A team of researchers from Durham University with colleagues from the Alfred Wegener Institute in Germany have been the first to enter and map previously uncharted waters in front of the North East Greenland Ice Stream on the ice breaker RV Polarstern.
The focus of the Durham group’s work is the investigation of the Northeast Greenland Ice Stream (NEGIS) and the large floating ice shelves that front it (79N Glacier and Zacharriae Isstrom). These two ice shelves buttress the flow of ice from the ice stream to the ocean and are the some of the last remaining in the Northern Hemisphere. In recent years they have begun to disintegrate raising concerns that this part of Greenland has started to respond to both rising air and ocean temperatures (Mouginot et al., 2015) and could potentially make a significant contribution to future sea-level rise.
Over the next four years the NEGIS project, led by Dr Dave Roberts and funded by the UK Natural Environment Research Council (Grant NE/N011228/1), aims to put these short term observations into a longer term context and establish how this sector of the Greenland Ice Sheet has evolved throughout the last 10,000yrs. Working both onshore and offshore the project will reconstruct ice sheet thickness, grounding line (where grounded ice changes to floating ice shelf) position, and ice shelf presence/absence. It will generate a time series of changes in ocean and atmospheric temperatures, thought to be key factors influencing the ice stream and ice shelf changes. These datasets will be used to test and model the sensitivity of the ice stream to different forcing mechanisms at 100 – 1000 yr timescales.
Cruise PS100 on the German ice breaker RV Polarstern is the first step towards gathering new information on the configuration and extent of NEGIS throughout the last 10,000yrs. The Durham team (Dave Roberts, Jerry Lloyd, Colm O’Cofaigh and Louise Callard) joined an international group of oceanographers, biologists, geochemists, geodeticists and seismologists on the RV Polarstern on July 18th and sailed north from Tromso, Norway. Having spent the first three weeks executing work in the Fram Strait led by Prof Torsten Kanzow (AWI) the ship moved onto the continental shelf offshore of NE Greenland working in Westwind Trough and then Norske Trough. Norske Trough is a deep trough that extends SE away from the Greenland coast. It has been hypothesised to have been a major ice flow pathway for the Greenland Ice Sheet during the last glacial cycle about 24-20,000 years ago and is now thought to play a major role in the advection of warm Atlantic Water on to the shelf. The plan was to sail from the outer continental shelf right up to ice shelf edge at 79N collecting oceanographic, geochemical, biological, geodetic and geological data as we went. This is a notoriously difficult area to access by ship due to the presence of pervasive, thick sea ice hence the need for the ice-breaking capability of RV Polarstern and the skill and experience of her exceptional crew.
In the Norske Trough the NEGIS team, supported by colleagues from the AWI bathymetry group, undertook several geophysical surveys and collected over 40 cores to shed new light on the poorly known history of the Greenland Ice Sheet in this region. On the seafloor we observed many distinctive geomorphological features such as moraines, grounding zone wedges, mega-scale glacial lineations and iceberg scours marking the former passage of the ice. They provide strong evidence for ice streaming to the shelf edge followed by grounding line retreat along the axis of the trough to the NW. After seven days sailing through heavy sea ice the ship reached the ice shelf of 79N Glacier on August 22nd; the first ship to ever sail so close to the ice shelf. With high pressure dominant over Greenland and favourable westerly winds the ship then spent an unforgettable week in front of the ice shelf. The Durham team have been able to survey and core the seafloor in front of the ice shelf and will now spend the next 4 years analysing the new data to reconstruct the history of the NEGIS and its ice shelves over the last few thousand years.
This is a beautiful part of the world. The sheer cliffs and blue sky forming the back-drop to mesmerising 79N ice shelf. The sea-scape has been amazing. The ship crashing through thick sea-ice day and night with switches between eerie fog, dazzling sunlight and glistening ice. We have also been lucky enough to see polar bears out on the ice in close proximity to the ship. We hope to return in 2017 with a land campaign supported by AWI via Station Nord and a second cruise (PS109) aboard the RV Polarstern.
The NEGIS project is supported through UK Natural Environment Research Council (NERC Grant NE/N011228/1) and through the Alfred Wegener Institute (Project N405) via the GRIFF I project and the RV Polarstern programme (Cruise PS100).