Greenland Ice Core Data Research Articles

Recent Environmental Change and Human Impact on Svalbard: The Lake-Sediment Geochemical Record

As part of a broader investigation into recent environmental change on Svalbard, the inorganic geochemical record of six lake-sediment cores was analysed. The major temporal trends in sediment elemental composition are driven by variations in two contrasting sediment components, both derived from catchment soils: (1) mineral matter, and (2) soil organic matter (SOM), enriched in Fe and Mn oxides and heavy metals. Two environmental impacts are recorded in most or all of the lake sediment sequences. An up-core increase in organic matter can be partly attributed to diagenetic effects, but also requires an enhanced supply of SOM relative to mineral matter. In addition, the central and southern sites all show a ca. 1970 event characterised by an enhanced mineral matter accumulation rate. This requires either an enhanced allochthonous supply or an enhanced mobilisation of littoral sediments. In either case a regional-scale driving force, such as a shift in climate, is required. At five of the lakes the sediment heavy metal concentration profiles can be explained entirely by natural factors. However, at Tenndammen (U), situated close to the Svalbard’s largest settlement at Longyearbyen, possible anthropogenic Pb enrichment is found. Comparison of observed and expected heavy metal profiles (based on Greenland ice-core data) shows that the lakes are generally too insensitive to have recorded a long-transported heavy metal pollution signal.

Cold event at 8200 yr B.P. recorded in annually laminated lake sediments in eastern Europe

A quantitative annual mean temperature reconstruction from an annually laminated lake-sediment sequence in Estonia, eastern Europe, shows a distinct cold period at 8400– 8080 yr B.P. (= before A.D. 2000); the timing is consistent with that seen in the Greenland ice-core data and various high-resolution records from western Europe. During maximal cooling at 8250–8150 yr B.P., the annual mean temperature in Estonia was ∼2.0 °C colder than prior to and ∼3.0 °C colder than after the cooling. The pollen-stratigraphic and sedimentological data suggest especially cold and snowy winter conditions. The duration and amplitude of the cold event agree with the modeled impact of a sudden freshening of the North Atlantic surface water and subsequent perturbation of the thermohaline circulation. Provided that the cold event was caused by a pulse of freshwater—from the melting Laurentide Ice Sheet—to the North Atlantic, the results indicate a strong teleconnection between the North Atlantic oceanic forcing and the east European climate at least up to long 26°E, mediated probably by the changing intensity of the zonal atmospheric circulation.

An investigation of rapid warm transitions during MIS2 and MIS3 using Greenland ice-core data and the CLIMBER-2 model

AbstractIn the search for abetter understanding of the dominant mechanisms of the Earth’s climate system, we present a study of rapid warm-climate transitions to Dansgaard– Oeschger events as seen in the ice cores from the Greenland ice sheet. We present a continuous δ18O record from the Greenland Icecore Project (GRIP) core with a resolution of 5 years until 50 kyr BP and of 20 years until 100 kyr BP. These data are compared with other high-resolution records, i.e. the Greenland Ice Sheet Project II (GISP2) chemistry record (25 years until 50 kyr BP) and the GRIP Ca2+ record (3 years until 100 kyr BP). All records have been transformed to the GISP2 Meese/Sowers time-scale. the high-resolution records are separated into interstadials and stadials, defined by the GRIP and GISP2 δ18O records. We examine in detail the transitions into the Dansgaard–Oeschger events, and propose a scenario for the changes that occur in the different ice-core records during the approximately 50 years the transition takes. Themain difference from previous studies is the much higher-resolution datasets available until 50 kyr BP; previous high-resolution studies by Taylor and others (1997) have focused on only the Younger Dryas/Preboreal transition. the data are compared to model simulations of the Dansgaard–Oeschger events performed with the CLIMBER-2 model of intermediate complexity (Petoukhov and others, 1998 ; Ganopolski and Rahmstorf, 2001).

Climate changes in northern China since the late Pleistocene and its response to global change

Nine representative high resolution profiles with reliable 14C chronologies have been chosen from the monsoon sensitive areas in China (winter monsoon from the north-west, and summer monsoon from the east) to provide a comparative picture of climate change within these areas. Comprehensive analyses of stratigraphic sequences and climatic proxy data have been used to reconstruct a history of fluctuating dry and wet environmental conditions in these monsoon sensitive areas since the last deglaciation. These records have also been compared with Greenland ice core and Guliya ice core data. Four major events representing these climate fluctuations (E1–E4) are recognised. Among them, E3 indicates an abrupt cooling event after the Younger Dryas interval. This event has so far only been recognised in China and high latitude areas in the northern hemisphere. It is proposed that century to millenial scale global temperature changes affect the intensity of monsoon circulation through ocean/atmosphere interactions, hence producing dry and wet climate fluctuations in monsoon sensitive areas. In an era of global warming, the overall picture presented by the sequences of wet/dry periods recorded in Chinese monsoon affected areas during the last deglaciation can be used as an historical analogue for future predictions of medium to long term climate change within these areas.

Late Quaternary sedimentation along a fjord to shelf (trough) transect, East Greenland ( c. 68° N)

Abstract The East Greenland continental margin between c. 66 and 68° N consists of a major fjord/trough system that extends from Kangerdlugssuaq Fjord, along Kangerdlugssuaq Trough to Denmark Strait. Measurements of the temperature and salinity of the water column along this transect indicates that ‘warm’ water (0–2°C) underlies the surface Polar Water of the East Greenland Current. A series of short (1–3 m) gravity cores along the fjord/trough transect have sufficient numbers of foraminifera that a suite of AMS 14 C dates has been obtained, including both basal and core-top age estimates. Rates of sediment accumulation vary through space and time; over the last 1 ka estimates vary from c. 3 to 0.1 m. These dates and measurements of sediment density, together with measurements of the percentages by weight of total organic carbon and biogenic silica, are used to show graphs of fluxes of the organic and inorganic sediment components over the last 1–14 ka. An analysis of the net flux of foraminifera indicates a reduction in numbers during the Younger Dryas chronozone and a general similarity with data from the Renland (East Greenland) ice core data.

Decadal Trends in the North Atlantic Oscillation: Regional Temperatures and Precipitation

Greenland ice-core data have revealed large decadal climate variations over the North Atlantic that can be related to a major source of low-frequency variability, the North Atlantic Oscillation. Over the past decade, the Oscillation has remained in one extreme phase during the winters, contributing significantly to the recent wintertime warmth across Europe and to cold conditions in the northwest Atlantic. An evaluation of the atmospheric moisture budget reveals coherent large-scale changes since 1980 that are linked to recent dry conditions over southern Europe and the Mediterranean, whereas northern Europe and parts of Scandinavia have generally experienced wetter than normal conditions.

Global pollution and its effect on the climate of the Arctic

This paper describes the potential effects of global pollution, primarily the greenhouse effect, on the climate of the Arctic. Climate models indicate an amplification of greenhouse warming in the Arctic but there are still many uncertainties about the magnitude and timing of the expected change. This paper focuses on these uncertainties by examining the changes observed in the temperature, sea ice extent, snow cover and permafrost regime of the Arctic. Since pollution is not the only climate-forcing factor, however, other external and internal driving forces are also examined, including solar influences, volcanic eruptions and changes in ocean circulation. Recent analyses of Greenland ice core data are beginning to cast serious doubt on our present understanding of the causes of climate change. Nevertheless, it is likely that global pollution is playing a major role in climate change. All the signals of change in the polar regions are consistent with the global greenhouse scenario. It cannot be stated unambiguously, however, that the greenhouse effect has already been observed in the Arctic, despite the fact that climate models indicate it to be largest there.

CO<sub>2</sub> measurements from polar ice cores: more data from different sites

Air in the bubbles of polar ice has in principal the same composition as the atmospheric air at the time of ice formation. Based on this relationship, an increase in atmospheric CO 2 since the beginning of industrialisation has been documented (Neftel et al. 1985, Pearman et al. 1986) in Antarctic ice cores. It has also been shown that the CO 2 concentration was much lower during the glacial period than in the preindustrial Holocene (Neftel et al. 1982, Barnola et al. 1987). These two results are well established. In this paper, we will discuss possible small deviations of the CO 2 concentration in air bubbles from that of the atmosphere at the time of enclosure. To do this, new results from Crete (Central Greenland) ice cores, covering the period since the beginning of industrialisation are presented, showing a good agreement with the data from Antarctic ice cores. In addition, the record of the atmospheric CO 2 concentration during the transition from the last glaciation to the Holocene and the fast variations in the concentration of atmospheric CO 2 during parts of the last glaciation, as suggested by Greenland ice core data, will be discussed. DOI: 10.1034/j.1600-0889.1991.t01-1-00003.x