Initial results from geophysical surveys and shallow coring of the Northeast Greenland Ice Stream (NEGIS)
- 1Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, Copenhagen 2100, Denmark
- 2Courant Institute of Mathematical Science, New York University, 251 Mercer St, New York, NY 10012, USA
- 3Physics Department, St Olaf College, 1520 St Olaf Ave, Northfield, MN 55057, USA
- 4Department of Geosciences and Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA 16802-6813, USA
- 5Department of Geosciences, University of Massachusetts Amherst, 611 North Pleasant St., Amherst, MA 01003-9297, USA
- 6Alfred Wegener Institute, Am Handelshafen 12, 27570 Bremerhaven, Germany
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.