Eemian Climate Research Articles

Continental European Eemian and early Würmian climate evolution: comparing signals using different quantitative reconstruction approaches based on pollen

Analyses of Eemian climate dynamics based on different reconstruction methods were conducted for several pollen sequences in the northern alpine foreland. The modern analogue and mutual climate sphere techniques used, which are briefly presented, complement one another with respect to comparable results. The reconstructions reveal the occurrence of at least two similar thermal periods, representing temperate oceanic conditions warmer and with a higher humidity than today. Intense changes of climate processes become obvious with a shift of winter temperatures of about 15 °C from the late Rissian to the first thermal optimum of the Eemian. The transition shows a pattern of summer temperatures and precipitation increasing more rapidly than winter temperatures. With the first optimum during the Pinus–Quercetum mixtum–Corylus phase (PQC) at an early stage of the Eemian and a second optimum period at a later stage, which is characterised by widespread Carpinus, climate gradients across the study area were less intense than today. Average winter temperatures vary between −1.9 and 0.4 °C (present-day −3.6 to 1.4 °C), summer temperatures between 17.8 and 19.6 °C (present-day 14 to 18.9 °C). The timberline expanded about 350 m when compared to the present-day limit represented by Pinus mugo. Whereas the maximum of temperature parameters is related to the first optimum, precipitation above 1100 mm is higher during the second warm period concomitant to somewhat reduced temperatures. Intermediate, smaller climate oscillations and a cooling becomes obvious, which admittedly represent moderate deterioration but not extreme chills. During the boreal semicontinental Eemian Pinus–Picea–Abies phase, another less distinct fluctuation occurs, initiating the oscillating shift from temperate to cold conditions.

High-resolution stratigraphic framework for Mediterranean sapropel S5: defining temporal relationships between records of Eemian climate variability

A high-resolution stratigraphic framework is presented for sapropel S5, which represents the low-mid latitude climate optimum of the previous interglacial period (Eemian). The framework is based on three sites along a transect from west to east through the eastern Mediterranean, and is further validated using a fourth site. This method allows expression of S5-based proxy records of Eemian climate variability along a standardised depth scale that offers unprecedented possibilities for assessment of spatial gradients and signal leads and lags in an interval where high-resolution (radiocarbon-style) dating cannot be performed. Our lateral comparison of S5 sapropels suggests that the onset of S5 in ODP site 967C (Eratosthenes seamount) was 1–6 centuries delayed relative to the onsets in more westerly sites.

Peregrinations of the Greenland Ice Sheet divide in the last glacial cycle: implications for central Greenland ice cores

The superb quality of the climate chronology archived in the Summit, Greenland ice cores (GRIP, GISP2) testifies that the Greenland Ice Sheet divide has been generally stable through the last glacial cycle. The ice sheet has experienced a broad range of paleoclimate conditions, ice sheet margin configurations, and internal dynamical adjustments in glacial–interglacial transitions, however. It is unlikely that the Summit region escaped shifts in ice divide position, geometry, elevation, and flow characteristics. Details of this dynamical history are important to several aspects of ice core studies. The magnitudes of pure and simple shearing, reconstruction of vertical ice velocity, the explicit location of the ice divide, and the divide ‘residence time’ at different locations are all of interest in interpretation of climatic variables and physical properties of ice in the ice cores. We apply a three-dimensional, thermomechanical ice sheet model to examine the evolution of these dynamical variables over the last 160 kyr in central Greenland. While a high-elevation ice dome is present in the Summit region throughout the simulation, ice divide migrations of up to 150 km are predicted. All points in the vicinity of the Summit ice cores, including the modern divide, have been subject to flowline shifts and variable, non-zero shear deformation during the adjustment from glacial to Holocene conditions, from ca. 10 ka to the present. Modelled divide peregrinations and strain rate history are consistent with the observed disturbance of deep ice in the GRIP and GISP2 ice cores, which has muddled paleoclimate reconstructions for the last interglacial (Eemian) period in Greenland. Dynamical excursions are also evident north of the modern summit, where the NGRIP ice core is currently being drilled [Dahl-Jensen et al., J. Glaciol. 43 (1997) 300–306]. However, the prevailing flow direction and deformation regime at the NGRIP site are much more stable than those at GRIP and GISP2 in the simulations. Combined with the greater depth of ice at this site, this lends cautious optimism to the hope that Eemian ice at NGRIP may contain an intact record of Eemian climate.

Climate variability in northwest greece during the last interglacial

Isotopic and palynological data over the period 115,000 to 135,000 years ago from a lacustrine sequence in northwest Greece show distinct oscillations during the intervals leading into and out of the full interglacial, whereas in between, changes were less pronounced but included a brief fluctuation. After peak interglacial conditions, temperatures decreased and precipitation increased in a series of steps. These data suggest that Eemian climate variability was similar to that of the Holocene both in terms of amplitude and, possibly, of pacing.

Tepsankumpu revisited - pollen evidence of stable Eemian climates in Finnish Lapland

Tepsankumpu revisited - pollen evidence of stable Eemian climates in Finnish Lapland

Tepsankumpu revisited — pollen evidence of stable Eemian climates in Finnish Lapland

Several till‐covered organic deposits, principally lake gyttja, in Finnish Lapland have been correlated with the last (i.e. Eemian) interglacial on the basis of their lithostratigraphic position and pollen stratigraphy. Most of the sequences are short, but together with three longer sequences from Finnish Lapland and one from Swedish Lapland (Leveäniemi) they provide a complete picture of Eemian vegetational and climatic development. The Tepsankumpu site was revisited, and the till‐covered thick freshwater gyttja deposit was studied in detail for pollen in order to search for signals of rapid climatic fluctuations postulated for the earlier part of the Eemian on the basis of Greenland ice core studies. The Eemian pollen stratigraphy in Finnish Lapland closely resembles the Holocene pollen stratigraphy of the area. The abundance of spruce and alder pollen suggests, however, more northerly limits for forest vegetation zones during the Eemian than during the Holocene. Oak also grew closer to Lapland, indicating a wanner climate than during the Holocene climatic optimum. The Tepsankumpu pollen stratigraphy indicates climatic stability over the entire time‐span it covers, i.e. the major part of the interglacial. This finding is in conflict with results from Greenland GRIP ice core studies and interpretations of some Continental European Eemian pollen diagrams.

A contribution towards the reconstruction of Eemian vegetation and climate in central Europe: First results of pollen and oxygen-isotope investigations from Mondsee, Austria

In this paper, the results of pollen analysis and oxygen-isotope investigations of two new cores from Mondsee are discussed. The climatic progression from the end of the penultimate glaciation to the end of the Eemian interglacial is compared with reconstructions from Bispingen and Grabern, northern Germany. The rise in temperature, between thePinus phase and the climate optimum in theCorylus phase, appears to have occurred in two steps. Evidence for climatic deterioration is first recorded during thePicea-Pinus phase, i.e. after theCarpinus phase. These reconstructions are in agreement with those based on the Grabern pollen data, but contrast with recent reconstructions based on the Bispingen pollen profile and the GRIP ice core from Greenland.

An analysis of Eemian climate in Western and Central Europe

On the basis of 31 pollen diagrams and additional data for botanical macrofossils an analysis is made of the Last Interglacial (Eemian) climatic history in Western and Central Europe. The main tool for this analysis is the climatic indicator species method. Only selected woody species are used for the quantification of data. Partial climatic range diagrams are presented for: Abies alba, Acer monspessulanum, Acer tataricum, Buxus sempervirens, Tilia tomentosa. The problem of time correlation and pollen zonation of the Eemian is discussed. The climatic analysis itself is based on an improved version of the indicator species method. In this version not every site is analysed for its climatic values. Instead maps and tables on the migrational history of Hedera, Ilex, Buxus, Abies and species of Acer, Tilia and Abies are the basis for climatic maps showing respectively January and July isotherms for the periods of the Corylus zone (E4a) and the Carpinus zone (E5). It is concluded that mean January temperatures were as much as 3°C higher at Amsterdam (The Netherlands), than at present, and mean temperatures in July were 2°C higher. However, the thermal maximum in winter was later (zone E5) than the summer thermal maximum (zone E4a). Winter temperatures changed parallel to rise and fall of global sea-level. Precipitation changes are more difficult to estimate. In the first part of the Eemian precipitation must have been relatively low, but from zone E4b onward it increased to higher values, reaching 800 mm and probably substantially more in zones E5 and E6. Hence the Eemian climate was in its beginning relatively more contintental, and later (from E4b onward) more oceanic. However, as compared with the Holocene, the Eemian climate was, generally speaking, more oceanic.

Eemian climate and pollen

Eemian climate and pollen

Eemian climate and pollen

Eemian climate and pollen

The Eem Stable Isotope Record along the GRIP Ice Core and Its Interpretation

A 3029-m-long deep ice core extending nearly to bedrock has been drilled at the very top of the Greenland ice sheet (Summit) by the Greenland Ice-core Project (GRIP), an international European joint effort organized by the European Science Foundation. The ice core reaches back to 250,000 yr B.P. according to dating based partly on stratigraphic methods and partly on ice-flow modeling. A continuous and detailed stable isotope (δ18O) profile along the entire core depicts dramatic temperature changes in Greenland through the last two glacial cycles, including abrupt climatic shifts during the Eem/Sangamon Interglaciation, which is elsewhere recorded as a warm and stable period. The stratigraphic continuity of the Eemian layers has therefore been scrutinized. New ice core studies, comprising cloudy band observations, deconvolution, and frequency analyses, lead to the conclusion that the climate instability suggested during the Eem Interglaciation in Greenland is likely to be real, though no conclusive evidence is available. Whereas latitudinal displacements of the North Atlantic Ocean current are considered the immediate cause of the glacial climate instability, longitudinal displacements may be the immediate cause of the Eemian instability. If so, the Eemian climate changes will be much subdued outside the Arctic region and will probably only be recognizable in sedimentary sequences of high sensitivity and temporal resolution.

Eemian climate fluctuations observed in a European pollen record

RECENT ice-core data from Greenland1,2 suggest that the climate during the last interglacial period (the Eemian) was more unstable than that of the Holocene (about 10,000 years ago to the present), being characterized in particular by a series of cold episodes each lasting about 70 to 750 years. Subsequent analysis of a second Greenland ice core3,4, however, failed to corroborate the details of these Eemian climate fluctuations, a result that may be attributable to the effects of ice flow4. To resolve this discrepancy, it is imperative to seek alternative sources of information about the Eemian climate. Here we present climate reconstructions from pollen data from the annually laminated Eemian lake-sediment record at Bispingen5 and from the Eemian and Holocene peat records at La Grande Pile6. The former record indicates that an initially warm period of 2,900 yr was followed by cooling and a series of colder episodes, one of which had winter temperatures comparable to those at the end of the preceding cold stage. The latter records show greater climate instability during the Eemian than the Holocene. These results are in broad agreement with those from the GRIP ice core, but contrast both with the GISP2 core3,4 and with recent high-resolution marine records from the North Atlantic7,8.

The role of the deep ocean in North Atlantic climate change between 70 and 130 kyr ago

THE suggestion1 that changes in North Atlantic Deep Water (NADW) production are linked through surface heat flux to the atmospheric temperature over Greenland is supported by earlier indications2,3 that NADW production decreased during glacial times, and by the subsequent finding4–6 that it declined during the Younger Dryas cool period at the end of the last glaciation. Changes in North Atlantic surface temperatures have been found7 to mirror high-frequency temperature changes recorded in Greenland ice cores over the past 80 kyr, but the connection to abyssal circulation has yet to be established, except for one or two isolated oscillations8,9. Here we present carbon and oxygen isotope analyses of benthic foraminifera in a high-resolution North Atlantic deep-sea sediment core for the period 70–130 kyr ago. These data allow us to reconstruct the history of NADW production, which shows a close correlation with Greenland climate variability for much of this time interval, suggesting that the climate influence of NADW variability was widespread. We see no evidence, however, for changes in NADW production during substage 5e (the Eemian interglacial period), in contrast with recent ice-core data10 which suggest severe climate instability in Greenland during this time period. Our results may support suggestions, based on data from a second ice core, that this apparent instability is an artefact caused by ice flow11. Alternatively, the Eemian climate instability may have had a different origin from the subsequent climate events.

Rapid interglacial climate fluctuations driven by North Atlantic ocean circulation

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.

Eemian interglacial record in the northwestern European part of the Soviet Union

In the territory under discussion, the Eemian period correlates with stage 5e of the deep-sea record. Continental and marine beds of the interglacial have been identified at more than a hundred sites. Pollen stratigraphy at the sites includes seven assemblage zones of wide geographical extent. The Eemian climate was milder and more humid than today. During the climate optimum the mean January temperature above the Baltic was 4–8°C higher. The author supports the theory on the connection between the Eemian and White Sea basins through the system of shallow sounds and the lakes of Onega and Ladoga. The Eemian deposits serve as an excellent key horizon for the study area, furnishing a good basis for palaeoclimatic conclusions and speculations for the future.

Are There Any Satisfactory Geologic Analogs for a Future Greenhouse Warming?

Abstract There have been numerous attempts to propose past warm time periods as “analogs” for a future greenhouse warming. In this paper it is argued that, although paleoclimate studies may provide important insights into process operating in the climate system, there may be no warm time period that is a satisfactory past analog for future climate. The future greenhouse warming may represent a unique climate realization in earth history. This conclusion is based on the following considerations: 1 ) comparisons with Holocene (9000 BP) or Eemian climates (120 000 BP) may be inappropriate because much of the variations in these climates can be explained in terms of seasonal rather than mean-annual forcing it has yet to be demonstrated that increased warmth for these intervals involved mew annual temperature increases that were globally synchronous, 2) comparisons with older and warmer climates (ex., Pliocene, Eocene, or Cretaceous) can be misleading because these warm periods had reduced polar ice cover, whe...

The Eemian interglacial and its termination

The development and termination of the Eemian interglacial is important because it may serve as a model showing how the present warm period might end in the event of no anthropogenic impact. The most important methods for studying the Eemian are outlined and critically evaluated. In spite of interpretation and dating problems, the various proxy data seem consistent enough to allow the conclusion that some 120,000 years ago the warm Eemian climate deteriorated rapidly and drastically. The forest vegetation in West Europe was replaced by a tundra type vegetation, and within 5000 or 10,OOO years the volume of continental ice grew to at least double the present volume, corresponding to a sea level 65 m, perhaps 90 m, below that of today. There is considerable disagreement between sea level estimates deduced from geological evidence and from benthic foraminifera oxygen isotope records.