Abstract: The (230)Th ages and (234)U/(238)U ratios were determined for Barbados corals that grew during periods of high sea level within the last 200,000 years. The similarity of the initial (234)U/(238)U ratios of some of the corals to the modern marine value suggests that these samples are pristine and that the marine (234)U/(238)U ratio 83,000 and 200,000 years ago was within 2 per mil of the modern value. The accuracies of the (230)Th ages are evaluated on the basis of the (234)U/(238)U values and a model of the behavior of uranium and thorium isotopes during diagenesis. For the last three interglacial and two intervening interstadial periods, sea level peaked at or after peaks in summer insolation in the Northern Hemisphere. This overall pattern supports the idea that glacial-interglacial cycles are caused by changes in Earth's orbital geometry. The sea-level drop at the end of the penultimate interglacial, the last interglacial, and a subsequent interstadial period lagged behind the decrease in insolation by 5,000 to 10,000 years.

Abstract: RAPID shifts in climate during the last glacial are now well documented, particularly from the oxygen isotope records of the two Greenland ice cores GRIP1,2 and GISP23. In the GRIP record1,2 these climate events are also seen during the preceding (Eemian) interglacial which may be an analogue for the future climate, warmed by the greenhouse effect. But these shifts are not found in the Eemian section of the GISP2 core3, casting doubt on whether the rapid shifts in the GRIP oxygen isotope record really do represent a climate signal. Here we present magnetic susceptibility, pollen and organic carbon records from maar lake deposits in the Massif Central, France. These data provide an independent record of past climate and we find that they correlate well with the ice-core records during the last glacial. During the Eemian, two rapid cooling events seen in our record also correlate with those seen in the GRIP ice core, supporting the idea that rapid climate change did occur in the Eemian interglacial and demonstrating that it extended to continental Europe.

Abstract: Large, abrupt shifts in the l8O/16O ratio found in Greenland ice must reflect real features of the climate system variability. These isotopic shifts can be viewed as a result of air temperature fluctuations, but determination of the cause of the changes—the most crucial issue for future climate concerns—requires a detailed understanding of the controls on isotopes in precipitation. Results from general circulation model experiments suggest that the sources of Greenland precipitation varied with different climate states, allowing dynamic atmospheric mechanisms for influencing the ice core isotope shifts.

Abstract: A core recovered from a thick sedimentary sequence in the Ioannina basin, on the western flank of the Pindus M ountain Range, northwest Greece, presents the opportunity to observe multiple changes in vegetational communities at one locality through a series of glacial-interglacial Q uaternary cycles. The Ioannina 249 record adds to the knowledge of vegetation history of areas of increased topographical variability and precipitation of the western Balkans and provides a complete stratigraphical record that can be compared with that of other long terrestrial sequences and with the marine record. Pollen analytical results are presented as percentages and concentrations, the former providing information on the composition and structure of vegetation, while the latter is considered here to be a reliable indication of vegetation density when changes differing by an order of magnitude are documented. The record shows an hierarchical order of variation in the response of vegetation to environmental change. Higher order of magnitude changes are alternations between forest and open vegetation communities, a reflection of major climatic shifts from interglacial to glacial modes. Superimposed on these oscillations is a lower order variability associated with vegetation changes within interglacial and glacial periods. During forest periods a succession is recorded with Quercus and Ulmus/Zelkova expanding early, followed by Carpinus betulus and also Ostrya carpinifolia/Carpinus orientalis , and finally Abies often accompanied by Fagus . Although individual periods may be characterized by dominance of one or more taxa, the underlying pattern of differential expansion is usually distinct and consistent. Nine forested intervals are distinguished and are assigned local names to facilitate longdistance comparisons and correlations. During open vegetation periods a series of changes is also observed from transitional steppe—forest or forest-steppe vegetation, through grassland steppe communities, culminating in a discontinuous desert-steppe vegetation. In addition to the two ends of the spectrum (forest and desert—steppe), attention is drawn to the intermediate phases representing ‘average’ Quaternary conditions. The Ioannina record is correlated with that of other long sequences from Europe and variation in the response of vegetation with site characteristics is considered. A strategy for long-distance correlations relying on the primary structure of vegetation and relative stratigraphical position of individual periods is described. The last interglacial period followed by two interstadials is recorded in much the same fashion in all records. Correlation of earlier periods was also in general agreement although only two continuous records that extend beyond the last interglacial are at present available for comparison. To minimize elements of circularity, similarities in the behaviour of individual taxa during particular periods are not part of the correlation criteria so that if their chronostratigraphical equivalence is independently corroborated their significance can be examined. On this basis, the importance of Carpinus betulus and the almost complete absence of Fagus on a subcontinental scale during the last interglacial are noted. Possible effects of climate, competition and disease are discussed. Cross-correlation with the deepsea oxygen isotope record provides a tentative chronology for the Ioannina record. Based on this, the sequence down to a depth of 162.75 m is considered to represent a record of approximately the past 423 000 years. Aspects of land-sea correlations are discussed in the light of the Ioannina 249 record and the importance of long sequences in the development of European Quaternary stratigraphy is emphasized.

Abstract: High-resolution stable-isotope and accelerator mass spectrometry 14C measurements in 25 box and piston cores from the Labrador Sea allow the reconstruction of major paleoceanographical changes during the last ~ 200 ka in this basin and also document the links between the interior of the Laurentide Ice Sheet and the North Atlantic Ocean during this interval. Two deep circulation regimes are indicated by contrasting sedimentation rates on the slopes: (i) the modern situation is characterized by a gyre of the North Atlantic Deep Water (NADW) components into the basin, which is responsible for the high-energy Western Boundary Undercurrent; this regime also prevailed during the former "true" interglacials and possibly during shorter "warm" intervals (e.g., Bolling-Allerod); (ii) a more frequent NADW-free situation during glacial and interstadial intervals is marked by the presence of a vertically homogeneous water mass in the basin. Sedimentological records also indicate that carbonate events (i.e., pulses of ...

Abstract: This paper presents a summary of the evidence for climatic changes during the last glacial-interglacial transition (14-9 ka BP) in land areas adjacent to the North Atlantic. It is a synthesis of the results of the 12 regional summaries compiled by contributors to the North Atlantic Seaboard Programme of IGCP-253 that are published separately in this issue of journal of Quaternary Science. Eighteen palaeotemperature curves are compared and arranged in three transects, one from southern Europe to Spitsbergen, a second from Ireland to Poland, and the third from southern New England to the Labrador-Baffin Shelf area. Ten maps are presented that summarise the synoptic climatic conditions of the region in 500-year time periods. The purpose of the exercise is to examine the extent to which any emerging patterns support the Ruddiman and Mclntyre model of large-scale shifts in the position of the oceanic Polar Front during the last glacial-interglacial transition. Some broad agreement emerges, although the influence of oceanic changes is diminished in areas that lay in close proximity to the Laurentide and Fennoscandian ice sheets. Attention is drawn to limitations in the compilations and to the potential for improved models in the future.

Abstract: CHANGING conditions in the North Atlantic region may drive global climate changes1,2. According to previous reconstructions of the last interglacial (the Eemian), North Atlantic sea surface tempera-tures (SSTs) were similar to present-day values3. In the Norwegian Sea, even warmer conditions appeared as a single pulse of short duration4,5, whereas the Greenland ice record suggests that the warm interglacial air temperatures were interrupted by several cold periods6. Here we use faunal and stable-isotope analyses of foraminifera in two sediment cores from the North Atlantic ocean and Norwegian Sea to reconstruct high-resolution records of SST and sea surface salinity (SSS) during the Eemian interglacial. Our results, which differ significantly from the Greenland record6, show a sharp decrease in SST and SSS of the Norwegian Sea, associated with a more moderate cooling and freshening of the North Atlantic at the middle of isotope substage 5e, several millennia before the beginning of continental ice-sheet growth. Changes in the Norweg-ian Sea surface conditions appear to have represented an important climate change affecting global atmospheric and thermohaline circulations.

Abstract: We examined coarse fraction contents of pelagic carbonates deposited between 2000- and 3700-m water depth in the tropical Indian Ocean using ocean Drilling Program (ODP) sites 722 (Owen Ridge, Arabian Sea) and 758 (Ninetyeast Ridge, eastern equatorial Indian Ocean), and four giant piston cores collected by the French RN Marion Dufresne during the SEYMAMA expedition. Over the last 1500 kyr, coarse fraction records display high-amplitude oscillations with an irregular wavelength on the order of approximately 500 kyr. These oscillations can be correlated throughout the entire equatorial Indian Ocean, from the Seychelles area eastward to the Ninetyeast Ridge, and into the Arabian Sea. Changes in grain size mainly result from changes in carbonate dissolution as evidenced by the positive relationship between coarse fraction content and a foraminiferal preservation index based on test fragmentation. The well-known `'mid-Brunhes dissolution cycle'' represents the last part of this irregular long-term dissolution oscillation. The origin of this long-term oscillation is still poorly understood. Our observations suggest that it is not a true cycle (it has an irregular wavelength) and we propose that it may result from long-term changes in Ca++ flux to the ocean. Sites 722 and 758 deltaO-18 records provide a high-resolution stratigraphy that allows a detailed intersite comparison of the two coarse fraction records over the last 1500 kyr. Site 722 (2030 m) lies above the present and late Pleistocene lysocline. The lysocline shoaled to the position of site 758 (2925 m) only during the interglacial intervals that occurred between about 300 and 500 ka (Peterson and Prell, 1985a). Despite these supralysoclinal positions of the two sites, short-term changes in coarse fraction contents are correlatable from one site to another and probably result from regional (or global) dissolution pulses. By stacking the normalized coarse fraction records from sites 722 and 758, we constructed a Composite Coarse Fraction Index (CCFI) curve in which most of the local signals cancelled out. The last 800 kyr of this curve appear to compare extremely well with the Composite Dissolution Index curve from core V34-53 (Ninetyeast Ridge), which unambiguously records past variations of carbonate dissolution in the equatorial Indian Ocean (Peterson and Prell, 1985a). In the late Pleistocene the CCFI variations are mainly associated with glacial-interglacial changes. They show strong 100 and 41 kyr periodicities but no clear precession-related periodicities. As proposed earlier by Peterson and Prell (1985a), the lack of precession frequencies may suggest that the regional carbonate dissolution signal is driven by changes in deepwater circulation. We cannot totally reject the possibility, however, that low temporal resolution and/or bioturbation degrade somehow the precessional signal at ODP sites 722 and 758. In contrast, spectral density of dissolution cycles in the giant (53 m long) piston core MD900963 (Maldives area) displays clear maxima centered on the precession frequencies (23 and 19 kyr-1) as well as on the 29-kyr-1 frequency but shows little power at the 100-kyr-1 frequency. These high-frequency changes most probably result from changes in surface productivity associated with monsoon variability. Dissolution at this site may be ultimately controlled by the oxidation of organic matter which appears to be incorporated into the sediments in greater quantity during periods of weak SW monsoon and/or increased dry NE monsoon.

Abstract: RECENT data from the GRIP ice core1–3 in Greenland suggest that the climate of the last (Eemian) interglacial period was much less stable than that of the present interglacial. Rapid transitions between warm and cold periods were found to occur on timescales of just a few decades. The North Atlantic climate during the Eemian period was also shown to be characterized by three states, respectively warmer than, similar to and colder than today1,2. Recent data from the nearby GISP2 ice core have revealed some discrepancies with these findings, which remain to be resolved4,5. Here we present simulations using an idealized global ocean model, which suggest that the North Atlantic ocean has three distinct circulation modes, each of which corresponds to a distinct climate state. We find that adding a simple random component to the mean freshwater flux (which forces circulation) can induce rapid transitions between these three modes. We suggest that increased variability in the hydrological cycle associated with the warmer Eemian climate could have caused transition between these distinct modes in the North Atlantic circulation, which may in turn account for the apparent rapid variability of the Eemian climate.

Abstract: FOSSIL hominids from the earlier Middle Pleistocene of Europe are very rare and the Mauer mandible is generally accepted as the most ancient, with an estimated age of 500 kyr1,2. We report here on the discovery of a human tibia, in association with stone tools, from calcareous silts at the Lower Palaeolithic site of Boxgrove, West Sussex, UK3,4 (Fig. 1). The silt units are correlated by mammalian biostratigraphy to an, as yet unnamed, major temper-ate stage or interglacial that immediately pre-dates the Anglian cold stage5. Accordingly, the temperate sediments are equated with oxygen isotope stage 13 (ref. 6) and are therefore roughly coeval with the Mauer mandible. The massive tibia is the oldest hominid fragment from the British Isles and provides the first information about the manufacturers of the early Acheulian industries of Europe. It is assigned to Homo cf. heidelbergensis.

Abstract: Thorium-230 ages of emergent marine deposits on Oahu, Hawaii, have a uniform distribution of ages from ∼114,000 to ∼131,000 years, indicating a duration for the last interglacial sea-level high stand of ∼17,000 years, in contrast to a duration of ∼8000 years inferred from the orbitally tuned marine oxygen isotope record. Sea level on Oahu rose to ≥1 to 2 meters higher than present by 131,000 years ago or ∼6000 years earlier than inferred from the marine record. Although the latter record suggests a shift back to glacial conditions beginning at ∼119,000 years ago, the Oahu coral ages indicate a near present sea level until ∼114,000 years ago.

Abstract: The δ13C record for organic carbon in Late Quaternary sediments of the Eastern Angola Basin shows a pronounced cyclicity with high values (-18.3 to -20‰) in glacial isotopic stages 2 to 4 and stage 6, and lower values (-20 to -21.2‰) in interglacial stages 1 and 5. Seasurface temperatures, derived from the alkenone Uk 37 index, vary in the opposite sense, ranging from 20–22°C in glacial stages up to 24–26°C in interglacial stages. The inverse relationship between δ13Corg and SST values suggests that the isotopic variations are not due to temperature-dependent isotopic fractionation during photosynthesis, in which case δ13Corg values would be expected to increase with increasing temperature. Relationships between sedimentary δ13Corg and C/N ratios indicate that differing proportions of marine and terrigenous organic matter can also be ruled out as a cause for the δ13Corg variability. Instead we conclude that changes in surface water CO2 concentrations were responsible for the observed glacial to interglacial isotopic variations.

Abstract: The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake. Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence. On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During glacial periods, the deep basin sediments of Lake Baikal are dominated by rapidly deposited clastics entering from large rivers with possibly glaciated headwaters. On the sublacustrine Academician Ridge (depth = 300 m), however, detailed analysis of the diatom biostratigraphy indicates that diastems (hiatuses of minor duration) and (or) highly variable rates of accumulation complicate paleolimnologic and paleoclimatic reconstructions from these records.

Abstract: Sediment cores from the South China and Sulu seas have been used to study sea surface temperature changes in these two western equatorial Pacific basins during the last 25,000 years. Sea surface temperature (SST) estimates were derived using the planktonic foraminiferal transfer function FP-12E previously developed by Thompson (1981). The water depths for the cores range from 500 m to more than 4,000 m and thus provide a good opportunity to evaluate the effect of carbonate dissolution on quantitative paleotemperature estimates. The sea surface temperature time series from shallow, well-preserved cores indicate that average winter and summer temperatures during the Holocene were approximately 27°C and 29.5°C, respectively, for both the South China and Sulu seas. These estimates agree well with modern observations. During the last glacial maximum, summer sea surface temperatures were approximately 28.5°C in the South China Sea and 29°C in the Sulu Sea and thus were very similar to the Holocene. In contrast, glacial winter sea surface temperatures are estimated at approximately 21°C for the South China Sea and 24°C for the Sulu Sea. This decrease in glacial winter sea surface temperatures results in a much larger seasonality during the last glacial (5°-8°C) compared to the Holocene (2°C). These seasonal contrasts are much greater than those estimated by Climate: Long-Range Investigation, Mapping, and Prediction Members (1981) for this region of the western equatorial Pacific. Variation in intensity of the monsoon system and surface water exchange rates between these basins and the open ocean are the major factors controlling glacial-interglacial SST fluctuations in the South China and Sulu seas. One factor influencing the accuracy of the SST estimates is the quality of preservation of the planktonic foraminiferal assemblages. Our results demonstrate that depth-dependent increases in dissolution result in systematically cooler SST estimates. This is due to the fact that warm water planktonic foraminifera tend to be more solution susceptible, and as dissolution progresses, the assemblage becomes enriched in the more resistant, cooler water taxa. Since dissolution is more intense during interglacials than glacials in the Pacific, dissolution tends to reduce the amplitude of the glacial-interglacial temperature difference.

Abstract: Late Pleistocene signals of calcium carbonate, organic carbon, and opaline silica concentration and accumulation are documented in a series of cores from a zonal/meridional/depth transect in the equatorial Atlantic Ocean to reconstruct the regional sedimentary history. Spectral analysis reveals that maxima and minima in biogenous sedimentation occur with glacial-interglacial cyclicity as a function of both (1) primary production at the sea surface modulated by orbitally forced variation in trade wind zonality and (2) destruction at the seafloor by variation in the chemical character of advected intermediate and deep water from high latitudes modulated by high-latitude ice volume. From these results a pattern emerges in which the relative proportion of signal variance from the productivity signal centered on the precessional (23 kyr) band decreases while that of the destruction signal centered on the obliquity (41 kyr) and eccentricity (100 kyr) periods increases below ∼3600-m ocean depth.

Abstract: The Renland ice core from East Greenland covers a full glacial cycle from the Holocene into the previous Eem interglacial. The first northern hemispheric record of both anions (Cl - , NO 3 - , SO 4 2- , CH 3 SO 3 - ), cations (Na + , NH 4 + , K + , Mg 2+ , Ca 2+ ), total amount of insoluble dust and acidity (measured as solid electrical conductivity) is extracted from this ice core in continuous profiles between 10 and 120 ka b.p. and from the 19th century. The ions measured are in balance during the interglacials but there is a large deficiency of anions during the glacial period. The ice is alkaline during most parts of the glacial period and Ca 2+ is the totally dominating ion therefore the deficiency of anions is probably due to carbonates (not measured). The concentration of most impurities is higher during glacial stages than the interglacials. The largest increase is found for crustally derived impurities (up to a factor of 10) while the sea salt elements are only slightly enhanced (less than a factor of 2). The concentration of impurities with a strong biogenic component is generally lower during glacial stages than the interglacials. A simple model tests the effect of changes in the physical conditions of the atmosphere influencing transport and deposition processes while keeping the source area and production rate constant. The model results show that the increased glacial concentrations observed for some impurities can be explained entirely by changes in transport and deposition, while the decrease in others may indicate a change in source emissions. The total content of impurities in the glacial atmosphere is higher if physical changes in the atmosphere rather than source emission changes are responsible for the variations observed in the Renland ice core. Thus, physical changes in the atmosphere can have a large impact on the radiative properties of the atmosphere and a climate forcing mechanism may be found in the dynamics of the atmosphere. However, a better understanding of the hydrological cycle and the general circulation of the atmosphere during glacial conditions has to be attained to be able to interpret influences on the global climate of a changed composition of the atmosphere from ice core data. DOI: 10.1034/j.1600-0889.1994.t01-4-00005.x

Abstract: Investigations in the lower Colorado River Valley, Gulf Coastal Plain of Texas, have resulted in the development of a spatially and temporally controlled history of changes in channel and flood-plain erosional and depositional processes. When combined with paleoclimatic and stratigraphic data from the upper Colorado River drainage and the record of glacio-eustasy in the Gulf of Mexico, this study permits evaluation of the relative influence of different external controls on channel and flood-plain behavior, the development of alluvial landforms, and the development of alluvial stratigraphic sequences. Late Pleistocene and Holocene alluvial deposits of the lower Colorado River have been subdivided into allostratigraphic units, with chronological control afforded by radiocarbon ages. In the bedrock-confined valley, up to 10 m of late Pleistocene (∼20,000-14,000 yr B.P.) sediments referred to as the Eagle Lake Alloformation (ELA) underlie a terrace at 17-20 m above the present-day channel. Deposition of the ELA was followed by bedrock valley incision, then deposition of a complex Holocene valley fill referred to as the Columbus Bend Alloformation (CBA). Columbus Bend Allomembers 1 and 2 (CBA-1 and CBA-2) underlie a terrace at 12-14 m above the present-day channel. CBA-1 was deposited ∼12,000-5,000 yr B.P., whereas CBA-2 was deposited ∼5,000-1,000 yr B.P. Columbus Bend Allomember 3 (CBA-3) consists of channel and flood-plain deposits that represent the past 600 yr of activity. Allostratigraphic units within the lower Colorado valley correlate with allostratigraphic units in major valley axes of the upper Colorado drainage and with records of climatic and environmental change, suggesting that alluvial deposits record basinwide responses to climatically controlled changes in discharge regimes and sediment supply. Basal unconformities for Holocene valley fills, however, appear to be 1,000-2,000 yr younger in the upper Colorado drainage than they are in the lower Colorado valley. This time-transgressioe episode of bedrock valley cutting was initiated by climatically controlled reductions in sediment supply, but conditioned by limits on rates of up-stream propagation of incision through a large drainage basin. By contrast, unconformities within Holocene valley fills document time-parallel episodes of flood-plain abandonment and soil formation, but little additional bedrock valley cutting, and indicate decreased flood magnitudes following shifts to drier climatic conditions. Flood-plain morphology and sedimentary facies changed through time in response to changes in climate coupled with a protracted degradation of upland soil mantles, which altered the rate at which precipitation was transferred to stream channels as runoff. During the late Pleistocene through middle Holocene, runoff was filtered through deep upland soils, floods were for the most part less flashy and contained within channel perimeters, and flood plains were constructed by lateral migration without significant vertical accretion; hence, the ELA and CBA-1 contain few vertical accretion facies. Exposure of bedrock surfaces during the late Holocene resulted in increased flood stages, deep overbank flooding, and construction of flood plains by vertical accretion; hence, CBA-2 and CBA-3 contain thick vertical accretion facies. Allostratigraphic units and bounding unconformities persist through the bedrock-confined valley to the Quaternary alluvial plain, but stratigraphic architecture changes substantially in the downstream direction as a result of the last glacio-eustatic cycle. On the alluvial plain, late Holocene CBA-2 and modern CBA-3, deposited contemporaneously with the present interglacial highstand, onlap and bury the ELA and CBA-1, which were emplaced during the last full glacial lowstand and the transgression that followed.

Abstract: We examined the existence of temperature ecotypes in seaweed species from the North Atlantic Ocean belonging to different biogeographic groups. Temperature ranges for survival, growth and reproduction were determined in culture for a total of 68 isolates belonging to 18 species. From the data, the reproductive seasonality and potential monthly growth yields in situ were estimated, and the adaptive significance of local ecotypes was assessed. Published palaeo-climatic reconstructions of glacial seawater temperatures were used to determine the importance of climatic change for the development of thermal ecotypes. In all cases highest annual growth yields were obtained by the southernmost populations. Although northernmost isolates had improved their growth capacities at low temperatures, local populations are still exposed to severely suboptimal conditions even in midsummer. There was no apparent relationship between the degree of latitudinal displacement during Pleistocene glacial/interglacial cycles and the development of ecotypes. On the other hand, in disjunct parts of the distribution, where populations have been exposed to different types of temperature stress through glacial/interglacial cycles, thermal ecotypes have evolved. In several cold-water species, western Atlantic populations have higher upper temperature limits for reproduction that those from the eastern Atlantic, which enhanced glacial persistence on the American coast. During the glaciation, eastern Mediterranean and Atlantic populations of tropical to warm temperate species were isolated from one another because of the existence of a cold water barrier near Gibraltar. The resultant lack of gene flow, combined with different types of temperature stress on the disjunct refuge populations, has been of major importance for the development of thermal ecotypes in the North Atlantic Ocean.

Abstract: During the last interglacial, sea level was as high as present, 4000 to 6000 years before peak Northern Hemisphere insolation receipt 126,000 years ago. The sea-level results are shown to be consistent with climate models, which simulate a 3° to 4°C July temperature increase from 140,000 to 130,000 years ago in high latitudes, with all Northern Hemisphere land areas being warmer than present by 130,000 years ago. The early warming occurs because obliquity peaked earlier than precession and because precession values were greater than present before peak precessional forcing occurred. These results indicate that a fuller understanding of the Milankovitch-climate connection requires consideration of fields other than just insolation forcing at 65°N.