scholarly journals A 1200 year record of accumulation from northern Greenland

1995 ◽  
Vol 21 ◽  
pp. 19-25 ◽  
Author(s):  
Arne Friedmann ◽  
John C. Moore ◽  
Thorsteinn Thorsteinsson ◽  
Josef Kipfstuhl ◽  
Hubertus Fischer
Keyword(s):  
Air Temperature ◽  
Little Ice Age ◽  
Accumulation Rate ◽  
Ice Cores ◽  
Ice Age ◽  
Greenhouse Warming ◽  
Accumulation Rates ◽  
Density Profiles ◽  
Secular Changes ◽  
Over Time

We present the first detailed study of regional and secular changes in accumulation rate from northern Greenland. Four 100–150 m ice cores from this previously little investigated region have been dielectrically profiled and a good chronology for all four ice cores established by modelling the density profiles and identifying volcanic peaks in the records. This made it possible to calculate the accumulation rates of each core. The current accumulation rates show that there is a large region of low accumulation rate to the northeast of central Greenland with drops in accumulation rate of 25% 150 km, and 50% 300 km from Summit.Relatively large variations in accumulation rate over time are seen in all the cores. We have compared the resulting accumulation-rate record, which should be related to changes in local air temperature over northern Greenland, with Scandinavian tree-ring records and have interpreted the data as showing an early Medieval Warm Epoch, but no pronounced “Little Ice Age” and no unequivocal greenhouse warming effect as yet in northern Greenland.

scholarly journals A 1200 year record of accumulation from northern Greenland

1995 ◽  
Vol 21 ◽  
pp. 19-25 ◽  
Author(s):  
Arne Friedmann ◽  
John C. Moore ◽  
Thorsteinn Thorsteinsson ◽  
Josef Kipfstuhl ◽  
Hubertus Fischer
Keyword(s):  
Air Temperature ◽  
Little Ice Age ◽  
Accumulation Rate ◽  
Ice Cores ◽  
Ice Age ◽  
Greenhouse Warming ◽  
Accumulation Rates ◽  
Density Profiles ◽  
Secular Changes ◽  
Over Time

We present the first detailed study of regional and secular changes in accumulation rate from northern Greenland. Four 100–150 m ice cores from this previously little investigated region have been dielectrically profiled and a good chronology for all four ice cores established by modelling the density profiles and identifying volcanic peaks in the records. This made it possible to calculate the accumulation rates of each core. The current accumulation rates show that there is a large region of low accumulation rate to the northeast of central Greenland with drops in accumulation rate of 25% 150 km, and 50% 300 km from Summit. Relatively large variations in accumulation rate over time are seen in all the cores. We have compared the resulting accumulation-rate record, which should be related to changes in local air temperature over northern Greenland, with Scandinavian tree-ring records and have interpreted the data as showing an early Medieval Warm Epoch, but no pronounced “Little Ice Age” and no unequivocal greenhouse warming effect as yet in northern Greenland.

scholarly journals Enhanced Moisture Delivery into Victoria Land, East Antarctica During the Early Last Interglacial: Implications for West Antarctic Ice Sheet Stability

2021 ◽  
Author(s):  
Yuzhen Yan ◽  
Nicole E. Spaulding ◽  
Michael L. Bender ◽  
Edward J. Brook ◽  
John A. Higgins ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Ice Cores ◽  
Snow Accumulation ◽  
East Antarctica ◽  
Ice Age ◽  
Accumulation Rates ◽  
Last Interglacial ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Victoria Land

Abstract. The S27 ice core, drilled in the Allan Hills Blue Ice Area of East Antarctica, is located in Southern Victoria Land ~80 km away from the present-day northern edge of the Ross Ice Shelf. Here, we utilize the reconstructed accumulation rate of S27 covering the Last Interglacial (LIG) period between 129 and 116 thousand years before present (ka) to infer moisture transport into the region. The accumulation rate is based on the ice age-gas age differences calculated from the ice chronology, which is constrained by the stable water isotopes of the ice, and an improved gas chronology based on measurements of oxygen isotopes of O2 in the trapped gases. The peak accumulation rate in S27 occurred at 128.2 ka, near the peak LIG warming in Antarctica. Even the most conservative estimate yields a six-fold increase in the accumulation rate in the LIG, whereas other Antarctic ice cores are typically characterized by a glacial-interglacial difference of a factor of two to three. While part of the increase in S27 accumulation rates must originate from changes in the large-scale atmospheric circulation, additional mechanisms are needed to explain the large changes. We hypothesize that the exceptionally high snow accumulation recorded in S27 reflects open-ocean conditions in the Ross Sea, created by reduced sea ice extent and increased polynya size, and perhaps by a southward retreat of the Ross Ice Shelf relative to its present-day position near the onset of LIG. The proposed ice shelf retreat would also be compatible with a sea-level high stand around 129 ka significantly sourced from West Antarctica. The peak in S27 accumulation rates is transient, suggesting that if the Ross Ice Shelf had indeed retreated during the early LIG, it would have re-advanced by 125 ka.

scholarly journals Enhanced moisture delivery into Victoria Land, East Antarctica, during the early Last Interglacial: implications for West Antarctic Ice Sheet stability

2021 ◽  
Vol 17 (5) ◽  
pp. 1841-1855
Author(s):  
Yuzhen Yan ◽  
Nicole E. Spaulding ◽  
Michael L. Bender ◽  
Edward J. Brook ◽  
John A. Higgins ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Ice Cores ◽  
Snow Accumulation ◽  
East Antarctica ◽  
Ice Age ◽  
Accumulation Rates ◽  
Last Interglacial ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Victoria Land

Abstract. The S27 ice core, drilled in the Allan Hills Blue Ice Area of East Antarctica, is located in southern Victoria Land, ∼80 km away from the present-day northern edge of the Ross Ice Shelf. Here, we utilize the reconstructed accumulation rate of S27 covering the Last Interglacial (LIG) period between 129 ka and 116 ka (where ka indicates thousands of years before present) to infer moisture transport into the region. The accumulation rate is based on the ice-age–gas-age differences calculated from the ice chronology, which is constrained by the stable water isotopes of the ice, and an improved gas chronology based on measurements of oxygen isotopes of O2 in the trapped gases. The peak accumulation rate in S27 occurred at 128.2 ka, near the peak LIG warming in Antarctica. Even the most conservative estimate yields an order-of-magnitude increase in the accumulation rate during the LIG maximum, whereas other Antarctic ice cores are typically characterized by a glacial–interglacial difference of a factor of 2 to 3. While part of the increase in S27 accumulation rates must originate from changes in the large-scale atmospheric circulation, additional mechanisms are needed to explain the large changes. We hypothesize that the exceptionally high snow accumulation recorded in S27 reflects open-ocean conditions in the Ross Sea, created by reduced sea ice extent and increased polynya size and perhaps by a southward retreat of the Ross Ice Shelf relative to its present-day position near the onset of the LIG. The proposed ice shelf retreat would also be compatible with a sea-level high stand around 129 ka significantly sourced from West Antarctica. The peak in S27 accumulation rates is transient, suggesting that if the Ross Ice Shelf had indeed retreated during the early LIG, it would have re-advanced by 125 ka.

scholarly journals Supraglacial debris-transport variability over time: examples from Switzerland and Iceland

1996 ◽  
Vol 22 ◽  
pp. 181-186 ◽  
Author(s):  
W.B. Whalley ◽  
C.F. Palmer ◽  
S.J. Hamilton ◽  
D. Kitchen
Keyword(s):  
19Th Century ◽  
Little Ice Age ◽  
Ice Age ◽  
Debris Transport ◽  
Actual Volume ◽  
Glacier Ice ◽  
Rock Glaciers ◽  
Slow Moving ◽  
The 19Th Century ◽  
Over Time

The volume of debris in the left-lateral, Little Ice Age (LIA:AD1550–1850) moraine of the Feegletscher, Valais, Switzerland was compared with the actual volume being transported currently by the glacier. The latter is smaller by a factor of about two. In Tröllaskagi, north Iceland, a surface cover of debris on top of a very slow moving glacier ice mass (glacier noir, rock glacier) has been dated by lichenometry. The age of the oldest part is commensurate with LIA moraines in the area. Knowing the volume of debris of a given age allows an estimate of the debris supply to the glacier in a given time. Again, there appears to have been a significant reduction in debris to the glacier since the turn of the 19th century. Debris input in the early LIA seems to have been particularly copious and this may be important in the formation of some glacier depositional forms such as rock glaciers.

scholarly journals Isotope Climatic Record Over The Last 2.5 KA from Dome C, Antarctica, Ice cores

1982 ◽  
Vol 3 ◽  
pp. 17-22 ◽  
Author(s):  
J. P. Benoist ◽  
J. Jouzel ◽  
C. Lorius ◽  
L. Merlivat ◽  
M. Pourchet
Keyword(s):  
Isotope Composition ◽  
Accumulation Rate ◽  
Maximum Amplitude ◽  
Ice Cores ◽  
Ice Age ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Temperature Changes ◽  
Low Pass ◽  
Climatic Record

Data on climatic changes over thousands of years is needed for a better understanding of the shorter term variations which are of interest to man. For this purpose we measured the isotope composition (δD‰) of two adjacent ice cores drilled in the Dome C area. The time scale was established using the remarkably constant mean annual accumulation rate (37 kg m−2) determined by various techniques. The detailed isotope records were smoothed to filter out the δ value fluctuations not directly related to local temperature changes. With respect to conditions over the last 2.5 ka, the combined smoothed δ curve indicates a cooler climate from about 1800 to 1200 AD and a slightly warmer period from about 1200 to 700 AD. These periods may well correspond to the suggested world-wide Little Ice Age and medieval warm phase. Using the present δD‰/T°C measured at the surface, the maximum amplitude for these two periods, after smoothing with a low pass filter of 512 a, is approximately -0.35 and +0.3°C, respectively.

scholarly journals Relation between recent glacier variations and climate in the Tien Shan mountains, central Asia

1992 ◽  
Vol 16 ◽  
pp. 11-16 ◽  
Author(s):  
Liu Chaohai ◽  
Han Tianding
Keyword(s):  
Mass Balance ◽  
Central Asia ◽  
Air Temperature ◽  
Little Ice Age ◽  
General Trend ◽  
Summer Temperature ◽  
Tien Shan ◽  
Ice Age ◽  
Climatic Fluctuations ◽  
Tien Shan Mountains

Since the Little Ice Age, most glaciers in the Tien Shan mountains have been retreating. Owing to an increase in precipitation in most parts of the mountains during the late 1950s to early 1970s, the percentage of receding glaciers and the speed of retreat have tended to decrease in the 1970s. However, the general trend of continuous glacier retreat remains unchanged, in part because the summer air temperature shows no tendency to decrease.In the Tien Shan mountains, as the degree of climatic continentality increases the mass balance becomes more dependent on summer temperature, and accumulation and ablation tend to be lower. Therefore, the responses of glaciers to climatic fluctuations in more continental areas are not synchronous with those in less continental areas, and the amplitude of the glacier variations becomes smaller.

Implications of rapid sediment accumulation in a small New England salt marsh

1992 ◽  
Vol 29 (9) ◽  
pp. 2013-2017 ◽  
Author(s):  
R. Scott Anderson ◽  
H. W. Borns Jr. ◽  
D. C. Smith ◽  
C. Race
Keyword(s):  
Salt Marsh ◽  
New England ◽  
Sea Level ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Sediment Supply ◽  
Greenhouse Warming ◽  
Accumulation Rates ◽  
Marsh Sediment ◽  
England Salt Marsh

The sediment accumulation rate within a small Spartina alterniflora marsh in Maine has been determined by measuring the amount of peat accretion on top of human-produced boards protruding from an exposed face of the marsh. Boards are at depths of 50–140 cm, suggesting sediment accumulation rates of 6.2–7.0 mm/year. Based on these data and a review of other relevant studies, aggradation in small marshes such as Shipyard Cove should be able to keep pace marginally with the anticipated sea-level rise due to "greenhouse" warming, given sufficient sediment supply. Local 19th century land clearance and subsequent erosion, activities that are greatly reduced today, probably supplied the bulk of the inorganic marsh sediment.

scholarly journals A first chronology for the NEEM ice core

2013 ◽  
Vol 9 (3) ◽  
pp. 2967-3013 ◽  
Author(s):  
S. O. Rasmussen ◽  
P. Abbott ◽  
T. Blunier ◽  
A. Bourne ◽  
E. Brook ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Ice Core ◽  
Conductivity Measurement ◽  
Ice Cores ◽  
Monte Carlo Analysis ◽  
Heat Diffusion ◽  
Ice Age ◽  
Age Difference ◽  
Electrical Conductivity Measurement ◽  
Volcanic Origin

Abstract. A stratigraphy-based chronology for the North Greenland Eemian Ice Drilling (NEEM) ice core has been derived by transferring the annual layer counted Greenland Ice Core Chronology 2005 (GICC05) from the NGRIP core to the NEEM core using 787 match points of mainly volcanic origin identified in the Electrical Conductivity Measurement (ECM) and Dielectrical Profiling (DEP) records. Tephra horizons found in both the NEEM and NGRIP ice cores are used to test the matching based on ECM and DEP and provide additional horizons used for the time scale transfer. A thinning function reflecting the accumulated strain along the core has been determined using a Dansgaard–Johnsen flow model and an isotope-dependent accumulation rate parameterization. Flow parameters are determined from Monte Carlo analysis constrained by the observed depth-age horizons. In order to construct a chronology for the gas phase, the ice age–gas age difference (Δage) has been reconstructed using a coupled firn densification–heat diffusion model. Temperature and accumulation inputs to the Δage model, initially derived from the water isotope proxies, have been adjusted to optimize the fit to timing constraints from δ15N of nitrogen and high-resolution methane data during the abrupt onsets of interstadials. The ice and gas chronologies and the corresponding thinning function represent the first chronology for the NEEM core, and based on both the flow and firn modelling results, the accumulation history for the NEEM site has been reconstructed, providing the necessary basis for further analysis of the records from NEEM.

scholarly journals Snow-accumulation rates and isotopic content (2H,3H) of near-surface firn from the Filchner-Ronne Ice Shelf, Antarctica

1994 ◽  
Vol 20 ◽  
pp. 121-128 ◽  
Author(s):  
W. Graf ◽  
H. Moser ◽  
O. Reinwarth ◽  
J. Kipfstuhl ◽  
H. Oerter ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Accumulation Rates ◽  
Ice Shelf ◽  
Near Surface ◽  
Surface Data ◽  
Chemical Profiles ◽  
Ice Edge ◽  
The Antarctic

The accumulation and distribution of the2H content of near-surface layers in the eastern part of the Ronne Ice Shelf were determined from 16 firn cores drilled to about 10 m depth during the Filchner IIIa and IV campaigns in 1990 and 1992, respectively. The cores were dated stratigraphically by seasonal δ2H variations in the firn. In addition,3H and high-resolution chemical profiles were used to assist in dating. Both the accumulation rate and the stable-isotope content decrease with increasing distance from the ice edge: the δ2H values range from about 195‰ at the ice edge to -25‰ at BAS sites 5 and 6, south of Henry Ice Rise, and the accumulation rates from about 210 to 90 kgm-2a-1. The δ2H values of the near-surface firn and the 10 m firn temperatures (Θ) at individual sites are very well correlated: dδ2H/dΘ = (10.3 ± 0.6)‰K-1; r = 0.97.The δ2H profiles of the two ice cores BI3 and BI5 drilled in 1990 and 1992 to 215 and 320 m depth, respectively, reflect the gradual depletion in2H in the firn upstream of the drill sites. Comparison with the surface data indicates that the ice above 142 m in core BIS and above 137 m in core BI3 was deposited on the ice shelf, whereas the deeper ice, down to 152.8 m depth, most probably originated from the margin of the Antarctic ice sheet.

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