Guidelines are determined for the spatial density and location of climatic variables (temperature and precipitation) that are appropriate for estimating the continental- to hemispheric-scale pattern of atmospheric circulation (sea-level pressure). Because instrumental records of temperature and precipitation simulate the climatic information that is contained in certain paleoenvironmental records (tree-ring, pollen, and written-documentary records, for example), these guidelines provide useful sampling strategies for reconstructing the pattern of atmospheric circulation from paleoenvironmental records. The statistical analysis uses a multiple linear regression model. The sampling strategies consist of changes in site density (from 0.5 to 2.5 sites per million square kilometers) and site location (from western North American sites only to sites in Japan, North America, and western Europe) of the climatic data. The results showed that the accuracy of specification of the pattern of sea-level pressure: (1) is improved if sites with climatic records are spread as uniformly as possible over the area of interest; (2) increases with increasing site density-at least up to the maximum site density used in this study; (3) is improved if sites cover an area that extends considerably beyond the limits of the area of interest. The accuracy of specification was lower for independent data than for the data that were used to develop the regression model; some skill was found for almost all sampling strategies.

Three characteristics of the output of a forest-stand simulation model were matched to pollen records of actual vegetation in central Tennessee. Temporal shifts of individual pollen taxon frequencies were compared to shifts of individual plant species frequencies in simulated biomass for the last 16,000 yr. Individual pollen profiles (temporally ordered species frequencies) were also compared to simulated biomass profiles during that period. Modern ratios of pollen to vegetation composition (R values) were compared with those calculated from simulated biomass percentages and fossil pollen percentages. The model output was similar to the comparable characteristics of the pollen record. The model output is therefore a plausible description of vegetation characteristics at the site of pollen deposition in central Tennessee. The model produced information unavailable from other sets of prehistoric data. This information describes the invasion and growth of the yellow-poplar which produces no windborne pollen, and of palynologically indistinguishable oak and pine species. These results suggest that many paleoecological questions can be answered through appropriate simulation modeling studies.

The Klutlan Glacier in the St. Elias Mountains of the Yukon Territory has surged repeatedly during the last few hundred years, and its drift-covered stagnant ice provides an analog for the downwastage, landform development, vegetational succession, and lake formation on Late Wisconsin moraines of Minnesota. Melting of the buried ice caused collapse of the drift mantle and the formation of lakes, which become filled with sediment that slumps in from receding ice walls. Topographic reversals are common, as the sediment cover of drained lakes inhibits local under-melting, and collapse occurs elsewhere. As the drift mantle thickens the land surface becomes stabilized and pioneer herbs are succeeded by shrubs and then by white spruce. The oldest moraines (600–1200 yr old) have a multiple-generation spruce forest, yet melting of buried ice still locally forms young lakes. Cores of organic sediment from the oldest lakes contain a stratigraphic sequence of pollen, diatoms and cladocerans that record the early stages in lake and landscape succession.

The quantitative distribution of planktonic foraminifera, pteropods, and coccolithophorids, as well as oxygen-isotope variations were analyzed in four deep-sea cores from the Gulf of Aqaba (Elat) and the northernmost Red Sea. The core record covers about 150,000 yr. Detailed stratigraphic subdivision is facilitated by combining all calcareous plankton groups. Time-stratigraphic correlation and dating beyond the radiocarbon range are possible by comparison of the oxygen-isotope curves. During the glacial maximum salinity rose to more than 50‰, while winter temperature of the upper waters fell by at least 4°C compared to the present. The rise in salinity can be accounted for by sea-strait dynamics and lowering of sea level. The Gulf of Aqaba and the Red Sea were continuously connected through the Straits of Tiran, and there is no indication of desiccation during the glacial maximum.

Interpretation of Deep Sea Drilling Project results and air-gun seismic profiles suggests that about 106 km3 of sediment have been eroded from eastern North America and southern Greenland and deposited in the adjacent North Atlantic since the beginning of continental glaciation. This volume is a minimum estimate which does not account for sediment beneath the continental shelf nor that portion carried south of the Blake-Bahama Outer Ridge by the Western Boundary Undercurrent. It represents erosion of about 100 m of solid rock and indicates that more than 90% of the sediment eroded from these areas was deposited as sands, silts, and clays in the adjacent western North Atlantic. Glaciation accounts for between 55 and 95 m of this average 100 m, and fluvial processes account for the remainder. The documented erosion in part substantiates W. A. White's (1972, Geological Society of America Bulletin83, 1037–1056) hypothesis of deep erosion and exhumation of shield regions, but is not in agreement with the entire volume of erosion implied by his model.

The Klutlan Glacier is a valley glacier 82-km long emerging from the Icefield Ranges of the St. Elias Mountains. It is one of at least 200 surging glaciers identified in western North America. During about the past 1200 yr, the glacier has deposited at its terminus a series of at least 7 surge-related Neoglacial ice-cored moraines. Lithologic characteristics of the Klutlan moraines suggest that they have resulted principally from the surging of the tributary Nesham Glacier, which periodically injects a lobe of medial and lateral moraines and the underlying ice into a more slowly moving Klutlan ice stream. Subsequent surges of the main ice carry the Nesham surge lobes to the Klutlan terminus as discrete geomorphic features. For the past 400 yr a Nesham lobe has reached the Klutlan terminus at approximately 80-yr intervals.

A seasonal reconstruction of the Indian Ocean during the last glacial maximum (∼18,000 yr B.P.) reveals that its surface circulation and sea surface temperature patterns were significantly different from the modern Indian Ocean. This reconstruction is based on the planktonic foraminiferal biogeography and estimated sea surface temperatures in 42 Indian Ocean samples. Compared to modern conditions, the polar front was 5° to 10° latitude further north during the last glacial maximum; the Subtropical Convergence was 2° to 5° latitude further north. The West Australian Current was more intense as part of the West Wind Drift was deflected northward along the coast of Australia. The Agulhas Current was cooler and weaker during the summer and more saline and subtropical during the winter. In general, the low latitudes underwent little temperature change. The western Arabian Sea was warmer which implies less upwelling and a weaker Southwest Monsoon. On the average, the Indian Ocean was 1.9°C cooler in February and 1.7°C cooler in August during the last glacial maximum.

14C ages supplemented by 230Th/234U determinations have been obtained for calcareous deposits on Koror, Babelthuap, Auluptagel, and Adorius Islands in the Palau Group, West Caroline Islands. Test borings for a bridge between Koror and Babelthuap reveal shoreface terraces consisting largely of bioclastic sand, but resembling fringing reefs. The base of the shoreface terraces dates to between 7000 and 8000 14C yr B.P. and the upper surfaces are slightly younger than 4000 yr B.P. Spacing of the subsurface isochrons indicates that the rate of sedimentation increased up-section on Koror terrace and decreased up-section on Babelthuap terrace. The average rate of deposition in the terraces was 0.5 cm/yr. Isochrons in the Babelthuap shoreface terrace are 7 m higher than those in the Koror terrace. If deposition was sufficient to keep the surfaces of the terraces at low tide level, then the Babelthuap side was essentially stable and the Koror side was uplifted between about 8000 and 6300 yr ago, and then subsided until 4000 yr ago; since then there has been about 2 m of uplift. “Top hat” microatolls on Koror terrace indicate that relative sea level has dropped about 30 cm in the past 75 yr. In the absence of good evidence for changes of level in water ponded in a moat, it is likely that the microatolls indicate uplift of the terrace. On the other hand, if tectonic activity was minimal, then differences in the two terraces are due to differences in sedimentation with the Koror side of the channel being substantially subtidal between about 7000 and 5000 yr B.P. Taking the composite eustatic sea-level curve of Hawaii and elsewhere as a reference standard, it is deduced that Auluptagel Island has risen 0.8 m in the last 2900 yr, and Adorius Island has risen approximately 8 m in the last 5000–6000 yr.

Modeling the combined hydrological and energy balances of Paleolake Chad and its drainage basin yields an estimate of at least 650 mm/yr for annual precipitation during portions of the early Holocene (10,000 to 5000 yr B.P.); the current rainfall in Chad Basin is 350 mm/yr. Two versions of the model are developed. The first version is one in which precipitation and lake area are linearly related. This version requires specification first of the area, net radiation, and Bowen ratio of the lake and second of the paleovegetation, net radiation, and Bowen ratio of the surrounding basin. In the second version of the model the ralationship between precipitation and lake area is nonlinear because the runoff ratio and Bowen ratio of the basin are made functions of precipitation. As the lake increases in area in response to increased precipitation, this version of the model allows for further increases in runoff (from the basin into the lake) as the vegetation changes from steppe to savanna and swamp. This nonlinear process may provide a partial explanation for the expansive paleolakes of the early Holocene. The results derived from both models are in good agreement with previously derived estimates of precipitation for North Africa during the early Holocene.

Research has demonstrated that leaf physiognomy is representative of the local or microclimate conditions under which plants grow. The physiognomy of leaf samples from Oregon, Michigan, Missouri, Tennessee, and the Panama Canal Zone has been related to the microclimate using Walter diagrams and Thornthwaite water-budget data. A technique to aid paleoclimatologists in identifying the nature of the microclimate from leaf physiognomy utilizes statistical procedures to classify leaf samples into one of six microclimate regimes based on leaf physiognomy information available from fossilized samples.

A series of ice-cored Neoglacial moraines at the terminus of the Klutlan Glacier covers an area of 90 km2. Studies were made to determine empirically how long ice persisted in the Klutlan moraines and to develop models that can accurately predict wastage rates under current climatic conditions. A meltout curve based on climatological data reflects the sum of three melting processes: surficial melting, melting by lake water, and melting by geothermal heat. About 950 yr are required to melt 180 m of ice with a debris concentration of 1%, or about 1200 yr for a 1.5% debris load. Another meltout curve, based on seismic data, suggests total meltout in about 875 yr. When all geologic factors are considered, the empirical meltout curve is remarkably similar to that derived by considering the major heat-flux parameters. Meltout rates can be predicted if (1) the fundamental climatic parameters can be ascertained, and (2) the sediment concentration in the ice is known.

Three units, correlatable with recent Lake Champlain, late-glacial marine Champlain Sea, and proglacial Lake Vermont sediments, have been identified from about 200 km of high-resolution seismic reflection profiles and eight piston cores collected in southern Lake Champlain. Lake Vermont deposits are nonfossiliferous and range from thin to absent nearshore and on bedrock highs to more than 126 m thick near Split Rock Point. Champlain Sea sediments contain marine foraminifers and ostracodes and are fairly uniform in thickness (20–30 m). Recent Lake Champlain sediments range in thickness from 0 to 25 m. Average sedimentation rates for Lake Vermont are considerably higher (4–8 cm/yr) than those for the Champlain Sea (0.8–1.2 cm/yr) and Lake Champlain (0.14–0.15 cm/yr). Bedrock, till, and deltaic and alluvial deposits were also identified on the acoustic records but were not sampled. An unconformity separating Champlain Sea deposits from Lake Champlain deposits is associated with numerous benches at water depths of 20–30 m. These benches, the alluvial deposits, and the onset of deltaic deposition are probably associated with a low water level stillstand at the close of the Champlain Sea episode.

The interaction between continential ice sheets and the planetary radiation budget is potentially important in climate-sensitivity studies. A simple ice-sheet model incorporated in an energybalance climate model provides a tool for studying this interaction in a quantitative way. Experiments in which the ice-sheet model is coupled step by step to the climate model show that ice sheets hardly affect the zonal mean radiation balance because the albedo feedback due to sea ice and snow cover is dominating. The model requires a 5% drop in the solar constant to create ice sheets of ice-age size.

If the feedback between surface elevation and ice-mass balance is included (in a very crude way), the ice-sheet size (L, measured southward from 70°N) becomes much more sensitive to in insolation. For a range of normalized solar constants, roughly from 0.98 to 1.02, two stable solutions exist: L ⋍ 0 and L ⋍ 2000 km. This result demonstrates that the response of ice sheets to insolation variations is far from linear. It also stresses the need for explicit modeling of the ice-mass balance of ice sheets, particularly its dependence on surface elevation.

The landform evolution of the Klutlan moraines is described and explained primarily with respect to processes that cause voids in which debris is deposited. Morainal deposits of different ages provide examples of landforms at different stages of development, so that continuous ideal evolutionary sequences can be inferred. Specific features are classified as those on material of the same depositional age that develop mostly in a vertical direction with numerous topographic reversals, and those cross-cutting materials of different depositional age that develop primarily in a horizontal direction. The evolution of slopes is often terminated by their destruction as the underlying ice melts, but former slopes on morainal debris are traceable to ice-ridge slopes on the original glacier surface. The general process of evolution is one of downwasting by surficial icemelt, in which a grand topographic reversal takes place as the original ice mass with a gently convex surface melts to leave a basin floored by a concave mantle of morainal debris. The primary glacial process of melting differs from the primary karst process of solution, but many minor glacial processes and major glacial forms are similar to minor karst processes and major karst forms.

Seven coprolites of the extinct Shasta ground sloth (Nothrotheriops shastense) were recently discovered in the Los Angeles County Museum collection from Shelter Cave, New Mexico. Three dung balls provided radiocarbon ages of 11,330, 12,330 and 12,430 yr B.P. Packrat (Neotoma) middens disclose a xeric juniper woodland at Shelter Cave during the sloth's occupation. Plant cuticles from the dung indicate that the ground sloth had a diet dominated by mormon tea (Ephedra) and other xerophytic shrubs. Pollen spectra from the coprolites have high representations of anemophilous plants and low representations of the dietary items shown in the cuticle analysis.

Fifteen radiocarbon dates of sloth dung obtained since 1974 strengthen the hypothesis that sloth extinction occurred about 11,000 yr B.P. Paleoenvironmental studies indicate that ground sloths lived in juniper woodlands and montane conifer communities. Nothrotheriops commonly dined on shrubs that are still present in these habitats. It is difficult to explain the demise of the Shasta ground sloth by climatic change or dietary stress. Human predation remains as a possible explanation; ground sloth extinction appears to coincide with the time of Clovis mammoth hunters.

Stratigraphic studies of pollen and macrofossils from six sites at different elevations in the White Mountains of New Hampshire demonstrate changes in the distributions of four coniferous tree species during the Holocene. Two species presently confined to low elevations extended farther up the mountain slopes during the early Holocene: white pine grew 350 m above its present limit beginning 9000 yr B.P., while hemlock grew 300–400 m above its present limit soon after the species immigrated to the region 7000 yr. B.P. Hemlock disappeared from the highest sites about 5000 yr B.P., but both species persisted at sites 50–350 m above their present limits until the Little Ice Age began a few centuries ago. The history of the two main high-elevation conifers is more difficult to interpret. Spruce and fir first occur near their present upper limits 9000 or 10,000 yr B.P. Fir persisted in abundance at elevations similar to those where it occurs today throughout the Holocene, while spruce became infrequent at all elevations from the beginning of the Holocene until 2000 yr B.P. These facts suggest a more complex series of changes than a mere upward shift of the modern environmental gradient. Nevertheless, we conclude that the minimum climatic change which would explain the upward extensions of hemlock and white pine is a rise in temperature, perhaps as much as 2°C. The interval of maximum warmth started 9000 yr B.P. and lasted at least until 5000 yr B.P., correlative with the Prairie Period in Minnesota.

The flora and vegetation of six ice-cored moraines of the Klutlan Glacier were analyzed in 65 plots by European plant-sociological techniques. The age of each plot was estimated from annual growth rings of shrubs or trees in the plots. Nine major vegetation types are distinguished: Crepis nana, Dryas drummondii, Hedysarum mackenzii, Hedysarum-Salix, Salix-Shepherdia canadensis, Picea-Salix, Picea-Arctostaphylos, Picea-Ledum, and Picea-Rhytidium. These contain plants aged 2–6, 9–23, 10–20, 24–30, 32–58, 58–80, 96–178, 177–240, and >163- >339 yr, respectively. Six other vegetation types are described from windthrow areas, drainage channels, volcanic tephra slopes, lake margins, fens, and drained lakes. The major vegetation types reflect a vegetational succession related to moraine age and stability, with the Crepis nana type as the pioneer vegetation developing through the other vegetation types to the Picea-Rhytidium type on the oldest moraines. Changes in species diversity and soil development, particularly humus accumulation, parallel the vegetational succession. This succession differs from patterns of revegetation of deglaciated landscapes in Alaska and British Columbia today and in Minnesota in late-Wisconsin times because of differences in climate, plant migration, and local ecology.

Cette étude est un premier essai de corrélation entre les résultats déjà obtenus sur les grandes faunes plio-pléistocènes européennes et les stades climatiques majeurs (tant froids que tempérés) mis en évidence dans les courbes isotopiques océaniques. Ce sont les phases froides en particulier qui expliquent souvent la disparition de certaines espèces, puis les phénomènes climatiques s'accentuant, leur remplacement par d'autres groupes. Un parallélisme assez évident se fait jour entre la succession en Europe des associations de grandes faunes et les phases paléoclimatiques révélées par le domaine marin, avec cependant une certaine dissension pour les périodes récentes. Face à la grande diversification des faunes quaternaires, dues vraisemblablement à la multiplicité des zones climatiques, et aux résultats des carottes océaniques qui nous fournissent seulement des données globales, seules les biostratigraphies régionales permettront de reconstituer avec précision les différents biotopes.

This study is the first test of correlation between the results obtained on the large Plio-Pleistocene European faunas and the main climatic stages (cold as well as temperate) demonstrated in marine isotopic records. In particular, there are cold stages which often explain the disappearance of some species, as well as climatic events that promote the substitution of some species by other groups. A rather evident parallelism appears between the European succession of large faunal associations and paleoclimatic stages revealed in oceanic areas, but some discordance occurs in the later periods. Faced with the great diversification of the Quaternary faunas, probably due to the multiplicity of climatic environments, and with global information from oceanic records, only local biostratigraphic studies will allow precise reconstruction of the different biotopes.

Data on soils with six Neoglacial moraines of the Klutlan Glacier have been compared with those from moraines at the warm, moist coastal site of Glacier Bay, 160 km south. Percentage organic matter increases rapidly for the first 100 to 150 yr of soil development and then continues to rise gradually for the next 100 yr. Soil pH falls from 8.0 in recent till to approximately 6.0 in 200-yr-old soils. Nitrogen levels in the mineral soil increase from near zero in recent tills to 0.7% in soils 175–200 yr old; organic horizons of soils associated with spruce forests in later successional stages contain approximately 1% nitrogen. Concentrations of certain inorganic phosphate ions in the different-aged soils increase continually throughout the succession. Data for nine chemical variables were subjected to a principal components analysis; the major pattern in the data reflects the differences between soils of low organic content and high pH present in early successional stages, and nutrient-rich soils with high organic content and low pH present after succession has progressed toward the spruce forest. These trends in soil development with time are strikingly similar to those reported from Glacier Bay, except that the changes in soil properties appear to be delayed by 50–100 yr at the Klutlan terminus. Although numerous signs of nitrogen deficiency have been identified in plants growing on new soils at Glacier Bay, none was observed visually in living plants or in nutrients measured in samples of foliage from three plant taxa (Epilobium latifolium, Salix spp., and Populus balsamifera) taken from the Klutlan moraines. Concentrations of nitrogen and other nutrients (Ca, Mg, K, total P) in the foliage samples show no clear trends with increasing soil development. Low temperatures, a short growing season, and very low mean annual precipitation probably limit plant growth and account for the delayed soil development on the Klutlan moraines.