Abstract
Abstract. The Northeast Greenland Ice Stream (NEGIS) is the sole interior Greenlandic ice stream. Fast flow initiates near the summit dome, and the ice stream terminates approximately 1000 km downstream in three large outlet glaciers that calve into the Greenland Sea. To better understand this important system, in the summer of 2012 we drilled a 67 m firn core and conducted ground-based radio-echo sounding (RES) and active-source seismic surveys at a site approximately 150 km downstream from the onset of streaming flow (NEGIS firn core, 75°37.61' N, 35°56.49' W). The site is representative of the upper part of the ice stream, while also being in a crevasse-free area for safe surface operations. Annual cycles were observed for insoluble dust, sodium and ammonium concentrations and for electrolytic conductivity, allowing a seasonally resolved chronology covering the past 400 yr. Annual layer thicknesses averaged 0.11 m ice equivalent (i.e.) for the period 1607–2011, although accumulation varied between 0.08 and 0.14 m i.e., likely due to flow-related changes in surface topography. Tracing of RES layers from the NGRIP (North Greenland Ice Core Project) ice core site shows that the ice at NEGIS preserves a climatic record of at least the past 51 kyr. We demonstrate that deep ice core drilling in this location can provide a reliable Holocene and late-glacial climate record, as well as helping to constrain the past dynamics and ice–lithosphere interactions of the Greenland Ice Sheet.
Highlights
Mass loss of the Greenland Ice Sheet (GIS) is accelerating (Rignot et al, 2011) due to multiple processes that are not fully understood (Wouters et al, 2013)
We demonstrate that deep ice core drilling in this location can provide a reliable Holocene and late-glacial climate record, as well as helping to constrain the past dynamics and ice–lithosphere interactions of the Greenland Ice Sheet
Diffusion has removed the annual signal of water isotope ratios, clear seasonality of the aforementioned chemical impurities can be observed in Fig. 5, such as anti-phasing of winter-deposited sodium and summer-deposited ammonium
Summary
Mass loss of the Greenland Ice Sheet (GIS) is accelerating (Rignot et al, 2011) due to multiple processes that are not fully understood (Wouters et al, 2013). 50 % of net Greenland mass loss has been attributed to increased ice stream discharge, with other mass loss mechanisms including changing patterns of surface accumulation and runoff (van den Broeke et al, 2009). The mechanisms governing ice stream discharge are complicated, and include bedrock conditions as well as buttressing effects at the ice sheet margin. P. Vallelonga et al.: Initial results from geophysical surveys and shallow coring mass-balance estimates (van den Broeke et al, 2009), but may be locally significant
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