Chlorine 36 fallout in the Summit Greenland Ice Core Project ice core

AbstractWe performed microscopic observations and a statistical study of the number, size and shape distribution of clathrates in the GRIP (Greenland Ice Core Project) deep ice core, using 185 samples from a depth range of 1016–3014 m, spanning a period of 6 to >110 ka BP and encompassing the Holocene, Wisconsin and Eemian periods. The number concentration of the clathrates varied considerably with climatic changes. It was possible to detect the rapid climatic oscillations in the last glacial between 13 and 110 ka BP, the Dansgaard–Oeschger cycles, in the number-concentration profile of clathrates. The mean volume of clathrates is less clearly influenced by climatic factors, with a tendency towards greater volumes in warmer periods, but also a growth of clathrates with depth could be detected. This growth rate was calculated to be 3.1 × 10-12 cm3 a-1. The amount of gases captured in the clathrates is estimated to be significantly smaller than the total amount of air determined by gas-concentration measurements. This points to diffusion processes of atmospheric gases within the ice matrix.

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Surface accumulation in Northern Central Greenland during the last 300 years

Annals of Glaciology ◽

10.1017/aog.2020.30 ◽

2020 ◽

Vol 61 (81) ◽

pp. 214-224 ◽

Cited By ~ 2

Author(s):

Nanna B. Karlsson ◽

Sebastian Razik ◽

Maria Hörhold ◽

Anna Winter ◽

Daniel Steinhage ◽

...

Keyword(s):

Large Scale ◽

Climate Models ◽

Regional Climate ◽

Ice Core ◽

Regional Climate Models ◽

Radar Data ◽

Accumulation Rates ◽

Ground Penetrating ◽

Core Project ◽

North Greenland

AbstractThe internal stratigraphy of snow and ice as imaged by ground-penetrating radar may serve as a source of information on past accumulation. This study presents results from two ground-based radar surveys conducted in Greenland in 2007 and 2015, respectively. The first survey was conducted during the traverse from the ice-core station NGRIP (North Greenland Ice Core Project) to the ice-core station NEEM (North Greenland Eemian Ice Drilling). The second survey was carried out during the traverse from NEEM to the ice-core station EGRIP (East Greenland Ice Core Project) and then onwards to Summit Station. The total length of the radar profiles is 1427 km. From the radar data, we retrieve the large-scale spatial variation of the accumulation rates in the interior of the ice sheet. The accumulation rates range from 0.11 to 0.26 m a−1 ice equivalent with the lowest values found in the northeastern sector towards EGRIP. We find no evidence of temporal or spatial changes in accumulation rates when comparing the 150-year average accumulation rates with the 321-year average accumulation rates. Comparisons with regional climate models reveal that the models underestimate accumulation rates by up to 35% in northeastern Greenland. Our results serve as a robust baseline to detect present changes in either surface accumulation rates or patterns.

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