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SMITHSONIAN MISCELLANEOUS COLLECTIONSVOLUME 82. NUMBER 6
THE PAST CLIMATE OF THE NORTHPOLAR REGION
BYEDWARD W. BERRYThe Johns Hopkins University
(Publication 3061)
CITY OF WASHINGTONPUBLISHED BY THE SMITHSONIAN INSTITUTIONAPRIL 9, 1930

SMITHSONIAN MISCELLANEOUS COLLECTIONSVOLUME 82, NUMBER 6
THE PAST CLIMATE OF THE NORTHPOLAR REGION
BYEDWARD W. BERRYThe Johns Hopkins University
Publication 306i i
CITY OF WASHINGTONPUBLISHED BY THE SMITHSONIAN INSTITUTIONAPRIL 9, 1930
ZU £or& (gafttmore (preesBALTIMORE, MD., U. S. A.
THE PAST CLIMATE OF THE NORTH POLAR REGION 1By EDWARD W. BERRYTHE JOHNS HOPKINS UNIVERSITYThe plants, coal beds, hairy mammoth and woolly rhinoceros ; thecorals, ammonites and the host of other marine organisms, chieflyinvertebrate but including ichthyosaurs and other saurians, that havebeen discovered beneath the snow and ice of boreal lands have alwaysmade a most powerful appeal to the imagination of explorers andgeologists. We forget entirely the modern whales, reindeer, musk ox,polar bear, and abundant Arctic marine life, and remember only theseemingly great contrast between the present and this subjective past.Nowhere on the earth is there such an apparent contrast between thepresent and geologic climates as in the polar regions and the mentalpictures which have been aroused and the theories by means of whichit has been sought to explain the fancied conditions of the past areall, at least in large part, highly imaginary.Occasionally a student like Nathorst (1911) has refused to becarried away by his imagination and has called to mind the mar-velously rich life of the present day Arctic seas, but for the mostpart those who have speculated on former climates have entirelyignored the results of Arctic oceanography. Recently, Kirk 2 has mar-shalled some of the evidence of the abundance of the present marinelife in the Arctic, and he concludes from this survey that marineorganisms are not dependable as indicators of geologic climates. 1think this conclusion is impregnable, and therefore if we are ever toget any information regarding past climates, the evidence will be fur-nished by fossil plants, and not too precisely either. Here againprudence is the watchword ; imagination must be entirely suppressed,and the distribution of recent plants must be understood and used.A correct solution of the problem is not only of prime interest togeologists and paleontologists but it offers assurance to geophysicistsconfronted with the now fashionable belief in wandering poles, and
'Given in summary before the Paleontological Society at the December, 1928,meeting.
'Kirk, Edwin, Fossil marine faunas as indicators of climatic conditions. Ann,Rep. Smithsonian Inst, for 1927, pp. 299-307, 1928.Smithsonian Miscellaneous Collections, Vol. 82, No. 6
2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82likewise comfort to meteorologists confronted with the traditionalview of a lack of climatic zones during most of the eons of earthhistory. I propose to pass in review what we know of the past dis-tribution of plants in the Arctic, after which I will endeavor to evaluatewhat they mean in terms of climate.Aside from some very scrappy plant fragments from the Silurianof Norway, the oldest traces of land plants in the north occur in rocksof Devonian age. Devonian plants have been discovered within theArctic Circle at the three localities shown on the accompanying map(fig. 1). These range from a few scraps, such as those found inEllesmere Land and Spitzbergen, to the extensive flora found onBear Island which embraces 31 named forms. These three florasare of upper Devonian age but not necessarily synchronous, since anearlier and a later horizon is represented on Bear Island and probablyon Spitzbergen.I have shown on the map (fig. 1) the occurrence of some otherDevonian floras outside the Arctic Circle and some in lower latitudesin order to give an idea of the known geographical range of Devonianplants in the present North Temperate Zone. The oldest of these isthe Lower Devonian flora of Roragen, Norway, embracing eightvery interesting forms. Of particular interest are the Middle Devonianplants found in silicified peats at Rhynie in northern Scotland andthe flora described recently from Germany, since these give us ourfirst considerable insight into the structure of these ancient plants.In looking over the list of identifications from Bear Island, allexcept Pseudobornia are seen to belong to widely distributed types,several are identical with species from the south of Ireland, and similarforms occur rather generally in lower latitudes. There are severalseams of coal at both the older and younger horizons, to whichBothrodendron contributed a large amount of material. Beneath thecoal seams are underclays with roots in place and the plant remainsshow no sorting—that is, delicate material is mixed with stems andbranches of all sizes—-both facts indicating conclusively that the bulkof the material was not transported but grew in the immediate vicinity.The same statement is true of the Devonian of Ellesmere Land.The plants of the Devonian are so remote from living forms thatI do not feel that any conclusions regarding the climate are warrantedbeyond the statement that they show that there were no climaticbarriers to prevent most of the types found in Latitude 45 to 50extending northward to Latitude 75 . There are, however, certaintypes which have not yet been found in the north, such as Eosper-
NO. 6 PAST CLIMATE OF NORTH POLAR REGION - BERRY
Fig. i.—Location of Devonian and Lower Carboniferous northern floras.1. Melville Island. Devonian2. Ellesmere Land. Devonian3. New Brunswick, Maine, etc. Devonian4. Northeast Greenland. Lower Carboniferous5. Spitzbergen: Devonian and Lower Carboniferous6. Bear Island. Devonian and Lower Carboniferous7. West Norway. Devonian8. Rhynie, etc. Scotland. Devonian9. Nova Zembla. Lower Carboniferous10. Northern Urals. Lower Carboniferous11. Siberia. Devonian.
4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. C2
matopteris from New York and Cladoxylon and Aneurophyton fromGermany, that may possibly indicate more genial climates in thoseplaces than obtained farther north, and Pseudobornia seems to be anorthern type, but until Devonian floras become much better knownno adequate conclusions can be reached.There are one or two points that deserve emphasis in this connection.These northern Devonian floras all consist of plants belonging to thePteridophyte, Arthrophyte, Psilophyte, Lepidophyte and Pteridospermphyla, and such existing representatives of these phyla as have sur-vived to the present, though few and not directly filiated, such asEquisetum and Lycopodium, are singularly unaffected by temperature.For example, there are now two species of Equisetum and oneof Lycopodium found within 10 degrees of the pole in northwesternGreenland (Ostenfeld, 1925). To be sure these modern Greenlandforms do not reach the size of their Devonian relatives, but this istrue of all existing members of these genera irrespective of latitude.Moreover, all of these northern Devonian plants appear to havebeen bog types. This conclusion is indicated by their forming coal inplace and by the structures disclosed in the silicified peats of Rhynie.Therefore, we conclude that the chief climatic factor was moisturerather than temperature. The fact that many of the Devonian plantswere palustrine also gives force to an observation which I haveelaborated in another place 1 that these Devonian plants while ancientand simple were not primitive and ancestral, but were the reduceddescendants of more highly organized ancestors. Since speculationwas to have no part in this discussion I refrain from elaborating myown belief regarding the more precise character of Devonian climate.LOWER CARBONIFEROUS(DlNANTIAN OR CULM)Fossil plants have been found in the Lower Carboniferous, orMississippian as Americans prefer to call it, at five or six localitieswithin or near the Arctic Circle. These floras range in extent froma few doubtful specimens at some localities to the 59 nominal speciesdescribed by Nathorst from Spitsbergen. The latter extend to 79North Latitude, and a considerable flora of similar species to thenumber of ten at least is found between 8o° and 81 ° North Latitudein northeast Greenland.
1 Berry, Edward W., Devonian Floras. Ainer. Journ. Sci., Vol. 14, pp. 100-120,1927.
NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY 5The Spitzbergen flora comprises 12 fernlike plants, 5 pteridosperms,1 arthrophyte, 25 lepidophytes, 1 cordaites (wood), and 15 of un-certain botanical affinities. Stigmarias and various roots occur inplace beneath the coal seams, showing that the vegetation was pre-served essentially in place ; and Lepidodendron stems have been col-lected up to 16 inches in diameter. There are no peculiar Arctic typesin this most extensive known Culm flora nor are there any generathat are not common to floras of the same age from lower latitudes.The single wood, Dadoxylon spetsbergense Gothan, fails to discloseany seasonal growth changes, which might be expected to result fromthe Arctic night. No other traces of the Cordaitales other than thiswood have been discovered here, which leads Nathorst to suggestthat the wood may have been carried by currents from some moresouthern clime, where also the woods fail to show growth rings.This may be true, but on the other hand there is great specific varia-tion in the degree to which growth rings develop in existing conifers,as Antevs has pointed out, and they tend to be absent under fairlyuniform conditions of humidity. That this is an individual trait ofthis particular species and is probably without climatic significance isshown by the presence or absence of rings in Devonian and Mississip-pian Dadoxylon woods from lower latitudes. For example, Dadoxylonbeinertianum Endlicher from Silesia, Dadoxylon TchicliatclicffianiuinEndlicher from Russia, and Dadoxylon vogesiacum Unger from theVosges, all of the same age as the Spitzbergen species, show distinctseasonal rings, but other contemporaneous European species fail toshow them.I cannot see any very conclusive indications of climate in theseLower Carboniferous floras, other than the fact that they extendedin places to within io degrees of the pole. Palustrine types pre-dominate as in the case of the Devonian, and more than half theknown forms are Lepidophytes which we have reason to believe show-little response to temperature. Sphenophyllums are entirely wantingin Spitzbergen, but are found farther north in Greenland and occuron Bear Island, so that their absence in Spitzbergen is merely anaccident of preservation or discovery. In general Arthrophytes aremuch rarer in the far north than in middle latitudes at this time andthe same seems to be true of a number of genera of large frondedfern-like plants, which is taken to indicate differences due to latitude.TRIASSICTriassic plants except in the latest or Rhaetic stage are scarcely,if at all known in the north polar region. There is a species of
C) SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82Schizoneura recorded from the New Siberian Islands which may beRhaetic and there are scattered Rhaetic plants in Greenland andSpitzbergen ; and somewhat farther south in northwestern Norway(Ando) and southern Sweden.The most extensive northern Rhaetic flora is that from ScoresbySound, East Greenland, between 70 ° and 71 ° North Latitude. Thiscomprises 51 named forms and several additional ones which are notnamed. Cycads and ferns predominate, and so far as we can judgeat this lapse of time all belong to cosmopolitan Rhaetic types. Harris,who has given an excellent account of these plants concludes thatthey indicate a temperate climate, largely on the ground of the pre-dominance of certain forms indicative of relatively pure stands andthe absence of mixtures such as occur in recent tropical assemblages.He concludes also, from a study of the cuticles of many of the species,that moisture was plentiful. The wood of Dadoxylon in the Rhaeticof Spitzbergen has very feebly marked seasonal rings.JURASSICSupposed Jurassic floras completely surround the pule and art'extensively developed throughout Siberia, in Alaska, Greenland, Spitz-bergen, Franz Josef Land, New Siberian Islands, and elsewhere.Formerly, many of these, as those in Siberia, were considered MiddleJurassic, but Nathorst is the authority for the statement that all ofthe more northern ones are post Oxfordian, and several, such as thatof Spitzbergen, are on the border between the Jurassic and the LowerCretaceous.The Spitzbergen flora is the most extensive and, according toNathorst, includes 2 horizons, one Portlandian and the other possiblyas young as Neocomian. A combined list of these comprises 57species, including 11 fern-like plants, 1 lepidophyte (Lycopodites),1 arthrophyte (Equisetites), 4 cycadophytes, 4 Ginkgoales, 23 conifersand 13 of uncertain affinities. Nine different types of coniferouswoods have been described and all show pronounced seasonal growthrings. Most of the generic types have a very great geographical range,but several, such as Phoenicopsis, Torellia and Drepanolepis, appearto be distinctly northern, and the predominance of conifers suggestsa cool temperate climate. They are found in sandstones associatedwith coal seams and freshwater mollusks (Lioplax, Unio) and evi-dently grew in the vicinity of their burial place.
NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY
Fig. 2.—Location of Triassici. Manchuria. Triassic and Jurassic2. Ussuri. Jurassic3. Amur. Jurassic4. Trans Baikal. Jurassic5. Irkutsk, etc. Jurassic6-10. Alaska. Turassic (?)11. Bathursy Island. Jurassic12. New Siberian Islands. Triassic (?)and Jurassic13. Mouth of Lena. Jurassic
and Jurassic northern floras.14. Solitude Island. Jurassic15. Franz Josef Land. Jurassic16. King Charles Land. Jurassic17. Spitzbergen. Triassic and Jurassic18. Northeast Greenland. JurassicTO. East Greenland. Jurassic20. Scoresby Sound. Triassic21. Ando, Norway. Triassic22. Scania. Triassic and Jurassic23. Scotland. Triassic and Jurassic.
8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82LOWER CRETACEOUSLower Cretaceous floras are found along the east coast of Asia,in Alaska, Greenland, and King Charles Land. From the last anumber of coniferous woods have been described by Gothan. Theseshow pronounced growth rings, said to be more prominent than inwoods of the same age from central Europe. Nathorst records anincomplete trunk 32 inches in diameter and showing 210 seasonalrings. The most extensive Arctic flora of Lower Cretaceous age isthat described by Heer from the Kome beds of western Greenland,but this, although generally considered to be of Barremian age, issubject to doubt as to age and content because collectors appear tohave mixed several Cretaceous horizons. As it stands in the literatureit comprises over 100 species, including 46 ferns (no less than 15are referred to Gleichenia, and although these surely represent thatgenus they are artificially multiplied), 1 marsilea, 1 lycopod, 3 equise-tums, 13 cycads, 20 conifers, 2 ginkgos, 5 monocotyledons, 3 or4 dicotyledons, and 6 of uncertain identity. The abundance of fernsindicates a humid climate as does the presence of coal. This floradiffers very little from those of corresponding age in lower latitudes(e. g., the Kootenai of western Canada and Montana)
.
UPPER CRETACEOUSStrictly Arctic Upper Cretaceous floras are limited to Alaska andGreenland but others of this age are found in northern Europe andeastern Asia. The most extensive is that from the two horizons inWest Greenland known as the Atane and Patoot beds. These havein large part been described by Heer and there is a great and un-warranted multiplication of species. That from the Atane beds has184 recorded species. It includes 31 ferns, 1 equisetum, 1 selaginella,1 marsilea, 12 cycads, 2 ginkgos, 25 conifers, 4 monocotyledons, 94dicotyledons and 14 of uncertain affinities.The seemingly most incompatible plant is the authentically deter-mined Artocarpus and this raises a question which cannot be decidedwithout prejudice. If a genus which is tropical at the present timeis found fossil associated with a preponderatingly temperate flora,which is to be given the most weight ? The one or the many, bearingin mind the latitude where they occur? My own feeling is that themajority are less likely to have altered their environmental require-ments than the minority, but this falls short of actual proof.The Patoot flora includes 19 ferns, 1 equisetum. 19 conifers, 2monocotyledons, 80 dicotyledons, and 2 uncertain.
NO. 6 PAS! CLIMATE OF NORTH POLAR REGION BERRY
Fig. 3.—Location of Cretaceous northern floras.1. Japan2. Sakhalin Island3-4. Siberia5. Klin6-8. Alaska9. Spitzbergen10. Queen Charlotte Islands
11. Vancouver Island12. Kootenai13. Mattagami. Ontario14. West Greenland (Kome, Atanc,Patoot)15. Scania[6. Wealden.
10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82TERTIARYTertiary plants from the Arctic have been encountered at verymany localities, usually associated with coal. This, and plants withtheir roots in place as in the case of Equisetum in Spitzbergen ; theassociation with fresh water mollusks, as in Greenland ; or aquaticbeetles, as in Spitzbergen and Iceland ; as also the presence of freshwater diatoms in the matrix and the mixtures of branches and delicatefoliage, prove conclusively that these Arctic floras and the associatedcoals cannot represent drift material from lower latitudes as somehave supposed. 1The similarity in facies and their mode of occurrence, as wellas the similar petrographic character of the intimately associatedbasalts suggest that all of these Tertiary Arctic floras are essentiallysimilar in age, although it is clear that in Spitzbergen, Alaska andprobably elsewhere, more than a single horizon is represented. Heer,the pioneer in this field, called them Miocene, just as Lesquereuxcalled the Fort Union and Wilcox floras Miocene, but the Arctic Ter-tiary floras are certainly older than Miocene and younger than Ft.Union. This is indicated by the determination of the so-called Kenaiflora of Alaska as of upper Eocene age, and if any one of them isproved to be upper Eocene none of the others can be older thanmiddle Eocene or younger than Oligocene. Collateral evidence of theirage is furnished by the age of the greatest extension of subtropicalfloras into the Temperate Zone, which is in upper Eocene (Jackson)to middle Oligocene (Vicksburg) time.Plants or coal of Tertiary age are found at the numerous widelydistributed localities shown on the accompanying sketch map (fig. 4).These completely encircle the pole and reach to within 83° of it(Grinnell Land). These will be treated at greater length than theolder floras because in some cases they are more extensive and alsobecause they consist very largely of species belonging to existinggenera, and hence can be discussed more intelligently than the olderfloras.It may be well at the start to dispose of an oft quoted assertion,as for instance " most of Heer's determinations were based uponleaves, which give no data for generic identification " (Gregory, op.cit.j p. 413). I would readily admit that much of Heer's material wasfragmentary, that he was over sanguine in some of his determinations,
1 Gregory makes much of this idea, which as we have seen is easily disproved.Gregory, J. W., Congres Geol. Intern. Compte rendu Xeme Session Mexico,1906, p. 413. 1907.
NO. (> PAST CLIMATE OF NORTH POLAR REGION BERRY I I
Fk;.4.—Location of Tertiary northern floras.i. Commander Islands2. Japan3. Sakhalin Island4-8. Eastern Siberia9-1 1. Northern Siberia12. Central Siberia13. Vancouver Island14. British Columbia15-18. Kenai19. Mouth of the Mackenzie20. Banks Land
21. Prince Patrick Island22. Melville Island23. Bathurst Island24. North Devon25-26. Ellesmere Land27-28. West Greenland29. New Siberian Islands30. Nova Zembla31. Spitzbergen32. Iceland33. North Ireland and Mull.
12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82
and described a great many more species than he should have done.Some genera do not have a characteristic leaf form, but to make sucha statement of genera such as Liquidambar, Betula, Corylus, Ulmus,Platanus, Sassafras, Liriodendron, Acer, Potamogeton, Cornus, andNymphaea, to mention but a few of those recorded from the ArcticTertiary, is the height of misunderstanding. Moreover, as I pointedout in 1922 (op. cit., p. 4) : " Plant fossils have this merit aside fromany question of botanical identification, and this feature seems to havebeen lost sight of by numerous critics of paleobotanical practise:that the size and form of leaves, their texture, the arrangement andcharacter of their stomata, and the seasonal changes in wood, affordcriteria that are quite as valuable climatically even though the speciesor genus to which they belong remains undetermined." Furthermore,a great many of the generic determinations are corroborated by fruitsand seeds, as for example, the genera Vitis, Acer, Nyssa, Hicoria,Juglans, Liriodendron, Fraxinus, etc.As recorded in the literature the number of species varies fromthe single Pinus recorded from Bathurst Island, 5 species from Elles-mere Land, 6 species from Banks Land to 55 species from Iceland,168 species from Spitzbergen, and 283 species from Greenland, thelast being greatly overelaborated. I have shown * that Heer's 30 speciesof fossil plants from Grinnell Land (Lat. 81 ° 42') represent not morethan half that number ; and that Viburnum, Alnus, Ulmus and Tiliarepresent Populus and Corylus. As thus revised the Grinnell Floracontains nothing extraordinary unless it be the supposed Nymphaearootstock and this may really belong to one of the plants representedby fragments of grasses or sedges.I will consider only the four most extensive of these floras in anydetail. These are Iceland, Spitzbergen, Greenland and Alaska.The Icelandic flora is preserved in tuffs, along with fresh-waterdiatoms, Unios, Potamogeton; and the wood and branches appearto have been broken off and buried by showers of ashes. The woodsshow sharply marked seasonal rings ; and conifers, willows, alders,birch, and hazel are prominent. The only plants certainly determinedthat might not justly be considered cool temperate are the following:Platanus, Liriodendron, Acer, Juglans, Ginkgo, Fraxinus, Hicoria.Representatives of all of these except Ginkgo, which is not a native,and Liriodendron, which reaches its northern limit in southern NewEngland, are hardy in northern New England (Platanus) or easternCanada (Acer, Juglans, Hicoria, Fraxinus) at the present time.
1 Berry, Edward W., Proc. Amer. Phil. Soc, Vol. 61, pp. 8-9, 1922.
NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY 1 1}The Spitzbergen flora comes from two horizons and the two total1 68 species and are not essentially different in facies. They are as-sociated with coal seams and are clearly continental palustrine associa-tions. There are 4 ferns, a Ginkgo, 27 conifers, 27 monocotyledonsand 80 dicotyledons. Three woods described by Gothan show markedseasonal rings. The warmer elements are Taxodinm, Platanns, Jug-lans, Nymphaja, Magnolia and Nyssa. Here also oaks, hazels, willows,poplars and conifers predominate. There is not a single tropical orsubtropical type and not one justly considered warm temperate.The Greenland Tertiary flora comprises 283 nominal species andincludes 8 fungi, 1 moss, 1 lycopod, 1 equisetum, 19 ferns (all tem-perate types), 1 Ginkgo, 28 conifers, 21 monocotyledons and 202dicotyledons. The petrified coniferous woods show well markedseasonal rings and the only genus that is seemingly out of place inthe far north is Taxodium, whose abundance in all Arctic floras andin proved temperate floras of other regions and other horizons showsthat it was not out of place here. The monocotyledons include mostlymiscellaneous leaf fragments, not generically determinable, as wellas two supposed palms (Flabellaria). It has frequently been pointedout by others as well as by myself that the nature of the last cannotbe considered as proving the presence of palms. The dicotyledonsare very much overelaborated. Probably 100 species is nearer thecorrect figure than the 202 which Heer differentiated.In Greenland as in all known Tertiary Arctic floras the leaves ofwillows, poplars, birches, and hazels predominate, but there are manyother genera whose identification cannot be disputed, such as Liquid-ambar, Alnus, Fagus, Quercus, Ulmus, Platanus, Sassafras, Fraxinus.Cornus, Liriodendron, Acer, etc. Vitis is represented by both leavesand seeds, and other genera also show fruits. The genera that appearto me to be highly questionable are the following: Castanea, Juglans,Pterocarya, Benzoin, Laurus, Myrsine, Apeiobopsis, Pterospermites,Zizyphus, Colutea, Dalbergia, Diospyros, Sapindus, and several others.I base this conclusion on the fossils and not on the probabilities oftheir presence. Some, such as Zizyphus and Ficus clearly do notrepresent those genera, in fact Fleer's discussion shows his lack ofconviction of the latter and he queried his determination.Heer devoted considerable space to a discussion of the climaticsignificance of this as well as other Arctic floras and concluded thatthe Greenland plants indicated a mean annual temperature of 53.6 F.,or a considerably lower figure than he estimated by the same methodsfor the supposed contemporaneous flora of Switzerland, thus clearlyrecognizing a climatic zonation.
14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82The so-called Kenai flora of Alaska was originally described byHeer and additions to it have been published by Lesquereux andKnowlton. Hollick has been engaged in a revision of this and relatedfloras from Alaska for a number of years, but his results are notyet published. That from the type locality as listed by Hollick in191 5 1 comprised but 40 named species and contains not a singletropical or subtropical type. Associated with the plants are thickcoal seams and fresh water mollusca (Unio, Anadon, Amicola, Mel-ania), as well as beetle elytra.He states in a recent letter that localities in the southeastern coastalregion of Alaska (Alexander Archipelago) have yielded a Tertiaryflora that is distinctly indicative of warmer climatic conditions thanthose from farther north, including cycads, palms, and such dicoty-ledonous genera as Anona, Dillenia, etc., but he has not yet determinedwhether they are the same or different in age. In either case they sup-port the conclusion that climatic zoning is indicated.As listed by Knowlton 2 in 1919 the Kenai flora (so called)comprised about 120 species. The most abundant forms are willows,oaks, poplars, walnuts, beeches, birches, hazels, and alders—dis-tinctly temperate, and cool rather than warm temperate types. Per-haps the most abundant plants individually, certainly the widest rang-ing geographically in northern latitudes (Holarctica), are the leavesof hazel bushes (Corylus). Of the 54 genera of Knowlton's list, thefollowing nine are not present in the existing flora of North America
:
Ginkgo, Glyptostrobus, Taxitcs, Hcdera, Paliurus, Elacodcndron,Pterospermitcs, Trapa, and Zizyphus.It may seem that I am juggling the evidence in omitting these ninegenera from further consideration, but let me point out that the threeof these about which there seems to be no doubt regarding their iden-tity, namely, Ginkgo, Trapa, and Glyptostrobus, are all temperate-types in the existing flora. The remaining six genera are under moreor less suspicion of quite a different order from any differences ofopinion among paleobotanists regarding the identification of the hazels,birches, alders, etc., with which they are associated. Opinion mightdiffer as to whether a particular species of the latter was a Betula orAlnns, an Ulmus or a Carpinus, or a Plancra; or whether one orseveral species of Corylus should be recognized as distinct species ; butopinion is unanimous that the choice is thus narrowed, whereas in thecase of such things as Taxites—all any one knows is that it represents
1 Hollick, A., U. S. Geol. Surv. Bull. 587, pp. 88-89, 1915.2 Knowlton, F. H., U. S. Geol. Surv. Bull. 696, pp. 786-789, 1919.
NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY 1
5
some Conifer. Why waste time trying to explain the climatic signifi-cance of Paliurus, a mostly extinct genus, when the particular fossilis probably not a Paliurus; or why concern oneself with an Arcticspecies of Zisyphus when the form in question is probably a Ceano-thusf I ask, can any one prove that the form-genus Ptcrospermitesis genetically related to the existing genus Pterospermumf or thatElaeodendron is a sound botanical identification ? I think not
!
On the other hand, the great mass of not only the Kenai but of allthe Arctic Tertiary floras are the readily recognizable, normal units ofa natural assemblage, which individually leave but slight room for dif-ferences of opinion regarding their identity. If fruits chance to befound in association with the leaves, they are such things as birch oralder cones, never the fruits of the " suspects " above mentioned.Of the remaining genera listed in the Kenai flora, all but the follow-ing six are represented in the existing flora of Canada: 2Esculus,Diospyros, Fiats, Liquidambar, Sequoia, and Taxodiuni. It may besaid of these that the Alsculus may not be an 2Escidus, but a Hicoria;that the two species that have been referred to Ficus do not belongin that genus; and that Sequoia is on the verge of extinction at thepresent time and its modern range bears little relation to its formerrange. The case of Sequoia is of especial interest in its bearing on mythesis. Formerly a Holarctic type, it survives today in a most re-stricted area particularly favored by humidity.The remaining genera of the Kenai flora appear to be determinedwith reasonable certainty. Not only are 39 of these represented inthe existing flora of Canada, but the following are still represented inthe existing flora of Alaska, or adjacent areas in northwesternCanada, or as far north as Labrador and Hudson Bay in easternCanada: Abies, Acer, Alnus, Alnites, Andromeda, Betirfa, Carex,Corylus, Equisetuiii, Fraxinus, Myrica, Osmunda, Phragmites(grass), Picca, Pinus, Populus, Prunus, Pteris, Oucrcus, Sacjittaria,Salix, Spiraea, Thuites, and Vaccinium.Seventeen of the Kenai species are conifers, and the only types thatwould seemingly be out of place in a cool temperate climate withwell-distributed moisture are Liquidambar, Paliurus, Taxodiuni, andZizypints. I have already given reasons for discrediting the deter-minations of some of these, and all of them have frequently beenfound fossil in temperate assemblages.The significant feature about these Eocene Arctic floras is thatthey show a comparable northward swing of not alone their northernlimits, but also of their southern limits, which in turn is comparableto the northward advance of the Jackson flora that I have considered
l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82
to be of the same age. The Jackson flora reaches Latitude 37 North.The most similar existing flora to that of the Jackson does not extendabove Latitude 26 North, and then only under especially favorableconditions of situation with respect to> warm ocean currents. This isa difference of 11 degrees. The flora of the Jackson was, moreover,a coastal flora, and I have not the slightest doubt but that had theMississippi embayment extended five degrees farther North, its shoreswould have been clothed with the same Jackson flora, for at that timesimilar floras are found in the Paris Basin in Latitude 49 ° North,in southern England in Latitude 51 ° North, and along the expandedMediterranean sea of the Old World.The southern limit of the contemporaneous " Arctic flora " is aboutLatitude 45 North in North America (British Columbia), and about57° North in Europe (Isle of Mull). It seems to me that the essentialconcordance of these facts is significant, and whatever may be thoughtof them, it would certainly seem to be difficult for any one to claim thatthese various Eocene floras mentioned do not show a climatic changein passing northward from the equator toward the pole. Moreover, atpresent—a time of. in many ways, an abnormal climate in a geologicsense ; with rather sharp zoning, although not nearly so sharp as thetextbooks would have us believe; a time of almost, if not quite, un-precedented land expansion in the Northern Planisphere, which Ibelieve expresses a casual relationship—the reliable members of theseEocene Arctic floras range much farther southward than they didin late Eocene time.EXISTING ARCTIC FLORASGreenland is the most illuminating of Arctic Lands because it ismuch the largest, and therefore more likely to preserve endemicspecies, and to receive immigrants from other Holarctic lands. Al-though mostly covered by ice which rises to an altitude of more than8,000 feet in the interior, it has island peaks (nunataks) with recentplants. Moreover the northeastern part appears never to have beenglaciated.About 400 species of recent vascular plants have been recordedfrom Greenland and at the south trees may reach heights of 10 or12 feet. North of the Arctic Circle the number of plants is fewer,but Ostenfeld (1925) records 125 species north of Latitude 76 and108 between Latitudes 78° and 8o°, including 2 equisetums, a lycopod,3 ferns, 32 monocotys and 70 dicotys, including Salix and Vaccinium.In an earlier paper (Ostenfeld, 1923) this author describes the floraof the north coast and records 70 species of plants from Latitude 82 .
NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY IJThis brief statement will be sufficient to indicate that there are otherand more important factors than cold. The almost entire absenceof vascular plants (a single species as I recall it) from Antarcticashows the part geography plays in the problem. The absence of treesin Lapland (Kihlman) shows the part taken by cold desiccating winds.The northern limits of many tree species in coastal Alaska and Nor-way will indicate the ameliorating climatic effects of warm ocean cur-rents and humidity.EXISTING ARCTIC CLIMATESThis is a complex subject which cannot be discussed in this con-nection beyond pointing out certain observed facts which support thethesis of the present discussion. These are the slower heating andcooling of water bodies as compared with land areas, with their respec-tive influence on air temperatures and pressures, their influence onthe amount of water vapor in the air and the resulting effect ofhumidity on equability.The climatic influence of the northward drift of oceanic watersmay be illustrated by the course of the present day isotherms over thenorth Atlantic, a somewhat hackneyed illustration but nevertheless themost striking. I am showing a few of the isotherms for January andJuly in figures 5 and 6. Those for January which show the full effectof the rapid radiation and quick cooling of the land, contrast mostmarkedly with the slow radiation and cooling of the ocean. At thistime the zero isotherm reaches Latitude 35 ° in Asia and about Lati-tude 74 north of Norway, a difference of 39 . Much the coldest placeis in northern Siberia which is io° to 20 ° colder than at the pole itself.The — 30 isotherm reaches almost to the pole north of the Atlanticand swings to approximately Latitude 55 ° in Siberia—a difference ofabout 35 of latitude. The midsummer isotherms naturally smoothout these curves somewhat but even at this season the isotherm of 5swings from about 62 in southern Greenland to 8o° just west ofSpitzbergen and the oceanic effect is clear as far eastward as NovaZembla.A few figures quoted from Sir John Murray's calculations willserve to emphasize the relations referred to. The energy radiatedby the lowering of the temperature of a cubic meter of water i° issufficient to raise the temperature of more than 3,000 cubic meters ofair i°, and a second calculation shows that the heat released by lower-ing by i° a stratum of water 200 meters deep and of 700,000 squarekilometers area would suffice to raise the temperature of a stratum
18
SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82
of air 4,000 meters deep over the whole of Europe on an averageof 10°.I have not attempted to evaluate the effects of the present ice capon Greenland or of the present altitude of the land surface, as all
Fig. 5.—Midwinter isotherms at the present time.
I wish to do in this brief discussion is to emphasize in a graphic waythe major thermal effect of land and water.The Arctic is an oceanic basin and shows a remarkable climaticcontrast with the elevated glacier-covered Antarctic continent. A fewof the probable climatic effects which would follow if the Arctic re-
NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY 19
ceived ocean waters from the Pacific or across Eurasia from ancientTethys, or became ice free during the summer are discussed verybriefly in a subsequent section of this paper.
20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82
tion that the flora of the Carboniferous grew in a supertropicalclimate with a humid atmosphere charged with carbon dioxide, ofwhich Koppen and Wegener make such specious use, had as itsoriginal basis the 18th century idea that the strange plants associatedwith the coal had been swept to Europe from the tropics by Noah'sflood and the further fact that the habit and venation of certain fern-like Carboniferous plants, now referred with strong probability tothe Pteridosperms, resembled certain existing tropical ferns.European students accustomed to the modern accumulations ofpeat in high latitudes concluded quite as illogically that peat couldnot accumulate in the present equatorial region because of the rapidoxidation there, so added carbon dioxide to make growth extraor-dinarily rapid and great moisture to prevent rapid oxidation. Thecarbon dioxide stimulation would also conveniently account for theenormous size O'f some of the calamites and lepidodendrons as com-pared with their diminutive survivors the equisetums and clubmosses.Then Koorders and Potonie described a peat bog from Sumatra andothers have been subsequently described from other tropical lands,and there has been much readjustment of views, which might havebeen accomplished much earlier if the experts on geological climateshad ever visited the tropics or even consulted the report on the peatdeposits of Florida published by the Geological Survey of that state.There is not space at my disposal to follow the vagaries of opinion,but it may be stated in the most positive way that temperature or theposition of any region with respect to the equator,1 that is betweenhot or cold climate, is not a factor in the formation of either peat orcoal. Second the tropical idea relies on representatives of long lived,vigorous groups with very many species, which either in the past orin the present have become adapted to a variety of habitats, as isusually the case in large vigorous groups of all kinds of organisms.As outstanding examples I may cite just a few types such as thepalms, and figs, or such genera as Cinnamomum and Zizyphus. Thegreat bulk of the existing palms are tropical and they are one of thefirst types of plants visualized when we think of tropical climates,whether we picture the Arab and his date palms or the South SeaIslander and his cocoanut palms. Nevertheless certain palms extendto approximately 39 ° South in Chile, 44 ° South in New Zealand,34 North in California, 35 ° North in North Carolina and 36° Northin Japan, and commonly are hardy several degrees north of their nat-ural limits, as in the Sacramento valley in California, or in southern
1 Not considering the subtropical arid belts of high pressures.
NO. 6 PAST CLIMATE OF NORTH POLAR REGION KERRY 21France. The greater limits of cultivated forms is usually not a resultof cultivation so much as it is of selecting the species that will growin a particular environment. In nature the proper species is subjectto the historical factor of there having been ancestors in the regionor in a region offering access to the particular region. For example ournative Californian palm (Neowashingtonia) is a plant of sandy alka-line soils whose range seems to be conditioned by the geologically latesubmergence of the Colorado Desert area, and to bear no relationshipto latitude. In the present tropics certain palms range upward tonearly 10,000 feet, as in the wet parts of the northern Andes(Ceroxylon, Geonoma, etc.).The genus Ficus, to which the cultivated fig belongs, is one withupwards of 600 existing species of a great variety of habitats, andwith probably as many fossil species, extending back to the dawn ofthe Upper Cretaceous. Various members range well into the temper-ate zone, both geographical and altitudinal. The cultivated fig gener-ally ripens its fruits in Baltimore. I have seen it in the temperatealtitudinal zone in Bolivia, and Weberbauer 1 records an altitudinalrange for it through 8,255 ieet m Peru.Cinnamomum is the genus to certain members of which the namescinnamon and camphor trees are applied. The genus is large andranges from the Upper Cretaceous to the present. Although the ma-jority of existing species are confined to the tropics some extend forconsiderable distances into the Temperate Zone, in fact the com-mercial supply of camphor comes in large part from Formosa andJapan, and the tree is hardy in the southern parts of the latter country.Introduced into Florida it has been widely seeded by birds and isperfectly hardy throughout that state.Zizyphus is a large genus also going back to the Upper Cretaceous,whose present center of population is southern Asia and the SundaIslands. The new world species are practically confined to> the tropics,but in the old world there are distinctly temperate species in southernEurope and eastern Asia. It has run wild in Louisiana, and charac-teristic fruits occur in the Pleistocene of the Atlantic coastal plain asfar north as Long Branch, New Jersey. Obviously as a fossil.Zizyphus entirely lacks a tropical significance.A third source of error is the common assumption that because aparticular type of plant has its home in the equatorial zone it is neces-sarily a tropical plant. The type most frequently alluded to in fossilArctic floras as indicative of a once tropical climate is the tree ferns.the term embracing a variety of species in several genera.
1 Weberbauer, A., Archiv. Asoc. Peruiana Progreso Ciencia, tomo 2, p. 60, 1922.
22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 52As a matter of fact tree ferns reach their maximum developmentin temperate rain forests, as in New Zealand (Lat. 40 S.), or insimilar situations in tropical uplands, as was pointed out by Alexandervon Humboldt over 100 years ago. They reach their greatest pro-fusion in South America in the temperate part of the montana zoneof the eastern Andes. They grow luxuriantly on the mountains ofcentral Africa at altitudes where they are buried in snow for part ofeach year, and as fossils their climatic significance is wet temperateand not tropical.There are a great many other genera or species in the same category.I have seen Anonas and Ingas (cultivated) at 10,000 feet in the Andesperfectly hardy, and a large number of generic types that are com-monly thought of as lowland tropical above the tropical altitudinalzone—such things as Dodonaca viscosa, Sapindus saponaria andSwietenia mahagoui. In fact it was my own observations in the Andesthat first turned me from the paleobotanic tropical tradition.Another misinterpreted type is the Gleichenia type of ferns (nowsegregated in several genera) very common in the Cretaceous florasof Greenland, but largely absent from the northern hemisphere inrecent floras. Although commonly confined to low latitudes at thepresent time, it is by no means confined to the tropical altitudinalzone; in fact, where I have seen it (Yungus of Bolivia) it is promi-nent above the tropical zone, as it is also in Hawaii, Peru, Ecuador,Asia, etc. Representatives reach 54 South in Chile and 40 Southin New Zealand.All this is related in any account of fern distribution (e.g., Dienatiirlichen Pflanzenfamilien, 1902), and still Gleichenias, along withpalms, cycads, and tree ferns always appear in the paleobotaniststropical repertoire.I suppose that constant reiteration of facts like the foregoing willhave to be continued over many years before the news reaches thosewho write on paleoclimatology, and at least another generation willelapse before writers of geological text books cease to talk about thetropical climate of Tertiary Greenland.Juniperus communis Linne is found as far north as the North Cape,which is at least 20 farther north than any other member of thefamily Cupressinaceae is found in the Eastern Hemisphere (Nat-horst, 1911). Sassafras, of the mostly tropical family Lauraceac. ex-tends northward to southern Maine, or about 13 beyond the bulkof the family. Diospyros, of the mostly tropical family Ebenaceae,extends northward to southern Connecticut, or about 12 beyond thebulk of the family.
NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY 27,Nor must it be lost sight of that at those times in the past whencertain groups were varied and abundant, as were the seed ferns inthe Paleozoic or the cycads in the Mesozoic, they were quite likelyto have shown the features of dominant organisms, both plant andanimal, and to have occupied more environmental niches than thedepleted survivors of the cycad phylum do at the present time.In Newfoundland and western Labrador the larch (Larix ameri-cana), the balsam poplar (Populns balsamifera), the paper birch(Betula papyrifera), and the balsam {Abies balsamea) fail to reachtbe Straits of Belle Isle (52 ) whereas they all extend far aboveLatitude 6o° in Alaska and the first crosses the Arctic Circle. Podo-carpus just fails to reach the Tropic of Cancer in Cuba. A Chileanspecies reaches 42 ° South Latitude in Chile. The northern limit offorests crosses the Arctic Circle in Alaska and reaches 70 ° NorthLatitude in Norway, the latter 20 north of the tree line on theAtlantic coast of North America.EXPLANATION OF PAST ARCTIC CLIMATESIt is perhaps fatuous to point out that climate, either present orpast, depends upon a variety of factors, both cosmic and terrestrial.Of the former the only one that is of practical importance is solar—that is, radiant energy from the sun, since it is inconceivable thatother heavenly bodies or the introduction of kinetic energy by meteor-ites exert any appreciable effect.The amount of solar energy reaching the earth depends upon thesun's activity, which is variable ; on the distance of the earth from thesun, which is also variable ; and more practically in so far as terrestrialclimates are concerned, on the condition of the earth's atmosphere,especially with respect to the amount of ozone, water vapor, carbondioxide, and dust present, all of which again are variable. The lati-tude, determining the angle of incidence of the sun's rays, is an obvi-ous factor, as is also the geographic pattern and the topography, in-cluding altitude under the latter. The geography determines whetherthe sun's energy falls on the land or the water, it determines thetemperature gradient between the equator and the poles and the con-sequent force of the planetary winds and ocean currents, and in lessobvious ways is of the greatest significance, as the following illus-tration will make clear.The North and South Equatorial currents in the Atlantic are sosituated that the South Equatorial, the stronger and the larger of thetwo. is divided by Cape San Roque into a larger, northern or Guianacurrent ; and a smaller, southern or Brazil current. Some authors.
24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82
c. g., Guppy, are inclined to consider the South Equatorial as bipartitethroughout, calling the Guiana current the Main Equatorial current.The point is immaterial in the present connection since all I desireto show is that the shape of eastern South America and the latitude ofCape San Roque are purely fortuitous in so far as their relation toclimate is concerned, and yet if the latter had happened to lie a few-degrees north of its present position much of the water that ultimatelycontributes to the Gulf Stream would have turned southward to aug-ment the Brazilian current, and the climate, especially of Europe andthe .Arctic, would lie profoundly modified, ft has been estimated thatif (ape San Roque were 2° north of its present position there wouldhe a shift of 40% of the Equatorial current which would be deflectedsouthward instead of northward. The same results would he attainedif the southern trades were not stronger and more constant than thenorthern trades, because of the relative amounts of land and waterin the northern and southern hemispheres.Scant attention will be devoted to the various theories that havebeen advanced to explain geological climates. These range from thatof Croll, in its original or modified form, based upon the eccentricityof the earth's orbit and the obliquity of the ecliptic, which was doubt-less a factor at all times, but hardly a controlling one ; through thosetheories that rely on changes in the atmosphere, such as alterationsin the amount of carbon dioxide (Tyndall, Arrhenius, Chamberlin) 1amounts of volcanic dust (Humphreys), to the extreme form of thehypothesis advanced by Manson, and elaborately defended by Knowl-ton, that a combination of cloudiness progressively diminishing dur-ing earth history, and a terrestrial control due to a cooling earth,instead of a solar control as at present, are the primary factors whichexplain past climates. Finally there are those highly speculativehypotheses such as Chamberlin's reversal of the oceanic circulation,and a group which predicate a wandering of the poles in variousways, now fashionable in the revived fonn put forward by Wegener.I have quite possibly omitted other proposals that might be men-tioned, and I have now to mention the theory, if it can be called atheory, wThich is the main thesis of the present paper, namely : thatit seems to me possible to interpret geological climates in the light ofdemonstrated changes in topography and geography, including underthe latter differences in the distribution of land and water and thetransfer of energy by currents.
1 it is of interest to note that Neumayr in 1883 pointed out that excesses of CO-would be impossible since the absorption by the oceans would maintain an almostperfect balance.
NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY 25This idea, as applied to the Pleistocene glaciation, was first advanced,I believe, by Lyell, and in its more general application has been re-cently put upon a scientific basis by Brooks, with whom I am in perfectagreement to the extent of the evaluation of these as major factors,but also in my firm conviction that arm chair philosophy with itsfondness for highly speculative and catastrophic hypotheses, has noplace in a uniformitarian world or in 20th century science, but be-longs in the medieval age of human thought.Climate, in a uniformitarian geology, occupies a somewhat anoma-lous position, which the scientific world has been slow to recognize,namely, that the history of the human race lias been run under cli-matic conditions which, from the point of view of earth history, areexceptional. Man was evolved subsequent to the relative elevationand the great extension of the continents which ushered in the Pleis-tocene glaciation, and therefore what is normal in human experience,is abnormal for the bulk of geological climate.While, therefore, we recognize that the climatic factors and themeteorological elements are the same now as always, their combina-tion to form actual climates has depended upon a great many factors,among the chief of which was the size, shape, position, and relativeelevation of the land masses. It may be remarked parentheticallythat numerous theories of the causes of, or descriptions of geologicalclimates have been advanced by students ignorant of meteorology,and also usually ignorant of the relationship of organisms to theirenvironments, and the last is strikingly true of Kdppen & Wegener'srecent Die Klimate der geologischen Vorzeit (1924).In attempting, a few years ago, to explain the extension of florasnearly to the poles during the late Eocene, I relied chiefly on the sub-mergence of continental areas in the middle Eocene and the resultingfree oceanic connections at that time between equatorial and Arcticwaters, pointing out that these Arctic floras were coastal floras andtherefore under the regime of an oceanic climate. 1 Essentially thesame explanation was put forward independently in connection withJurassic climates a few months later by Kerner von Marilaun.2 Anadditional and important factor has since been brought forward byBrooks,* who points out that the temperate gradient is a simple func-tion, whereas the influence of the ice increases as the square of the
1 Berry, Edward W., A possible explanation of upper Eocene climates. Proc.Amer. Phil. Soc, Vol. 61, pp. 1-14, 1922.2 Kerner von Marilaun, F., Sitz. k. Akad. Wiss. Wien, 1922.
'Brooks, C. E. P., The problem of mild polar climates. Quart. Journ. Roy.Meteor. Soc, Vol. 51, pp. 83-94, I925-
26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82
radius. Hence a coincidence of minor factors sufficient to effect anoverturn in the one or the other direction, that is, toward ice forma-tion or melting, would suffice to induce a wide extension of polarice, or to prevent the polar regions from maintaining a permanentice cap. If this is true then it seems quite probable that there was littlepolar ice during those times already enumerated when temperatefloras invaded the polar regions. This would mean profound changesin the distribution of barometric pressures and consequent wind cir-culation, and in fact, in all of the elements which constitute climate.It would mean that in western Greenland, for example, where themost extensive late Eocene Arctic flora has been found, the presentday glacial anti-cyclonic winds would be replaced by westerly or south-westerly winds blowing from the relatively warmed waters of BaffinsBay, and this would satisfactorily explain the details of the floralfacies. This does not mean that there would be tropical climatesin the Arctic or that the region would not be ice bound in the winterseason. The protective effect of snow, and cold sufficient to causea cessation of plant activity during the Arctic night are a physiologicalnecessity. Otherwise most vascular plants could not maintain them-selves. They tend to die either if active in darkness or if exposedto desiccation by air and wind when the ground water is frozen.Regarding the general history of discussions of geologic climatesI believe that most paleontologists who have written on this topic,especially those dealing with the pre Cenozoic periods, have had littlebasis in fact for their speculations. They seem to me to be utterlyoblivious to the great amount of modern work on the distributionof marine organisms ; and their ideas of the climatic significance of atrilobite, eurypterid, or ammonite is purely a tradition inheritedfrom the distant past when all strange organisms were associated withtorrid climates.In stating my belief in a greater uniformity of climate during thepast than obtains at the present I do not wish to be understood asadvocating such unsound beliefs as the entire absence of zonation,such as many paleobotanists have defended (Jeffrey, Knowlton), ora similar uniformity throughout all time. Both are equally disprovedboth by geological observations and meteorological principles. Jeffrey,for example (Anatomy of Woody Plants, Chapter XXX, 1917), holdsthat the more ancient the epoch the warmer the climate, and that therehas been a gradual and progressive refrigeration during geologictime ; that the organization of secondary wood in extinct plants furn-ishes the most reliable evidence of climatic conditions ; that towardthe end of the Paleozoic, growth rings appeared in woods in highlatitudes ; that in the Triassic, growth rings were developed ten degrees
NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY 2."
nearer the equator than had been the case during the Paleozoic ; that inthe Jurassic, the tracheids first developed tangential pitting whichwas at the end of the annual ring, and accompanied by storage ele-ments (wood parenchyma).None of the statements in the foregoing paragraph are facts ofobservation. There is no geological or paleontological evidence indi-cating a progressive climatic cooling during geologic time, and thePermo-Carboniferous glaciation was admittedly more extensive thanthat of the Pleistocene. The presence or absence of growth ringsexhibits what might be called constitutional variations quite indepen-dent of climate, not that they really are independent, but two associatedspecies under an identical climate will behave differently with respectto this feature of their anatomy. Growth rings appear in some Pale-ozoic woods many degrees nearer the equator than Jeffrey admits, 1and in marine formations deposited off low coasts so that they cannotbe considered to have been upland types. Several Lower Carbonifer-ous examples have already been cited. The Paleozoic genus Mesoxy-lon shows tangential pitting, which, according to Jeffrey, first appearedin the Jurassic; and the citation of a wood from the Triassic ofArizona as an argument for the advance equatorward of cooler cli-mates during the early Mesozoic is particularly disingenuous, as itis perfectly clear that the growth rings in this case have nothing to dowith temperature, but are due to periodic lack of moisture in thatregion, as exemplified by the contemporaneous gypsum deposits.Similarly in the recent elaborate work on geologic climates by Kop-pen & Wegener, already alluded to, these authors offer explanationsto account for climates during the successive geologic periods, whichclimates have not been proved to have ever existed.As I have pointed out on previous occasions, paleobotanists ingeneral have entirely lacked objective experience outside the temper-ate zone, and have invariably overestimated temperatures. They havebeen prone to use the present distribution of the fancied or real rela-tives of their fossil forms as if temperature were the sole factor in theenvironment, and have stopped with the geographic occurrence, withthe apparently simple trust that all lands in the equatorial zone were atsea level and wet tropical. A sojourn in the Arctic climate beneaththe equator on the backbone of South America would do much tocorrect this misapprehension, as would also some experience in thetemperate rain forests of different regions.I had intended to indicate current conceptions of contemporaneouspaleogeography on the maps showing the plant localities but have
1 Several have been named in the preceding paragraph devoted to MississippianArctic plants and others could be added.
28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82
not clone so although I did publish such a map for the Eocene in 1922.This intention was abandoned for the reason that it was not possibleto compile maps that did not cover too much time nor in which theextrapolation was not so great as to destroy any real value.Arldt has compiled maps which represent a synthesis of opinionsand showing the areas of agreement and disagreement among special-ists and to these the reader is referred. The debatable North Atlanticcontinent and the Gondwana continent would, if they ever existed,have had a profound effect on climate. Whether or not they wereever realities I am not prepared to say. I can, however, make thefollowing statements with a considerable degree of certainty, namely
:
That there was a wide extent of land in the Northern Hemisphere fromlate Mississippian through the Permian. That the Arctic was land-locked in early and middle Triassic and that there was a wide trans-gression of the sea in the Neo Triassic. That the maximum Jurassictransgression was about Oxfordian ; that of the Lower Cretaceous wasin the Neocomian ; that of the Upper Cretaceous was in the Emscher-ian ; that the late middle Eocene was a time of wide sea transgressionand low lying lands ; and that during the Miocene, the age to whichHeer assigned the Arctic Tertiary floras, the amount of land in theNorthern Hemisphere was nearly as great as it is at the present time.It will be seen that there is a correspondence between times of seaextension and Arctic floras and times of land extension and no tracesof Arctic floras. This correspondence is not exact, and so little ofpaleogeography is objective, that I would not want to appraise it formore than it is worth, but in so far as it is known it does offercorroboration of my thesis.I had expected to attempt an estimate of the meteorological condi-tions at the various times at which fossil floras are found in the Arctic,but after abandoning any hope of getting reliable paleogeographicdata I have also abandoned the former. Brooks has published someinteresting meteorological estimates using as a basis those parts ofArldt's maps where authorities agree, but it should be pointed out thatmajorities are quite as likely to be wrong in science as in politics, andif generalizations are valid (which of course they are not) thenminorities are usually right.There are, however, a few considerations that may be put forwardas having a high degree of validity, namely the importance of ice asa third factor, added to the long recognized rotational (planetary) andgeographic (distribution of land and water and altitude) factorsin influencing the distribution of pressures and consequently of pre-vailing winds. And also the effect of the volume of fresh water car-
NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY 20.
ried into the Arctic basin by rivers in the formation of ice and theeffect of current-borne ice in maintaining subnormal density and con-sequently the identity of the present day cold currents as they movesouthward. Once they become of normal density they disappear belowthe surface and lose their climatic influence.Another factor of considerable importance climatically, especiallyin connection with the theory of Brooks, is the amount of reflectionfrom the earth's surface. I do not have the exact figures, but estimatesgiven to me orally by \Y. J. Humphreys, are about 7 per cent fromland or water and about 70 per cent, or ten times as much, from thesurface of snow and ice. If there has been the wide fluctuations inpolar ice as Brooks predicts, then reflection is a factor which can notbe safely neglected.At the present time in high latitudes the prevailing wind circula-tion is easterly with a southward moving component at the surface.If the ice cap were gone we would have westerly winds in high lati-tudes with a poleward component at the surface.
I f Bering Strait was open and less shallow, a great volume of warmPacific water would pour into the Arctic and greatly ameliorate theclimate, as would also be the case if a Cretaceous seaway bisectedNorth America, or a Devonian or Eocene seaway bisected Eurasia,such as are shown on current paleogeographic maps. If the best avail-able sources are utilized in plotting Eocene seaways nearly all theTertiary coal occurrences and floras in the Arctic range themselvesalong the easterly coasts of such seaways.CONCLUSIONSThe major factor in the polar extent of temperate floras isnot primarily the direct effect of temperature so much as it is the factthat above 32 F. water is a liquid and below 32 F. it is a solid. AsaGray said "Plants are the thermometers of the ages." I have nodoubt that terrestrial vegetation when properly interpreted is the safest
^uide to geological climates, but as thermometers they are prettypoor and we have no means of calibrating them.There is no unequivocal botanical evidence of tropical or subtropicalclimates at any time in the Arctic. There is no evidence from paleo-botany of a lack of climatic zonation at any geological period fromwhich fossil plants are known, although at such times the evidencepoints to a relative mildness and a lack of sharp zonation, as com-pared with the present.The distribution of the known fossil Arctic floras with respectto the present pole proves conclusively, as Seward pointed out in1892 (p. 53). that there could have been no wandering pole.