Research onshore Greenland

RV 'POLARSTERN' ARK-XXIV/3
Reykjavik – Bremerhaven
7 September to 13 September 2009

At the beginning of the week we still continued to recover the ocean bottom seismometers. Some of the instruments were placed close to submarine volcanoes to record small earthquakes coming from the interior of the volcano. Such earthquakes can be generated by movements in the crust and/or by ascending magma in the volcano itself. One of the objectives was to monitor with the help of earthquakes how tectonically active the investigated area of the Knipovich Ridge is. On Spitsbergen, for instance, such earthquakes cannot be recorded with sensors since the quakes are too weak. On Tuesday, we successfully finished this part of our program. All instruments were recovered as planned. In the middle of the week, the ship sailed southward to measure heatflow along a profile starting around 100 km east of Shannon Island. The distance between the heatflow stations varies between 40 and 80 km. Meanwhile, our geologists got accustomed to life onboard the ship again. Following is their report from the onshore camp:

The group of geologists was picked up on 1st September from their field camp at around 80°N and were now back onboard again. During the two weeks in the field, 10 lakes in total were explored. Some of the lakes were very shallow and became ice-covered again at the end of the field season. For the first time in this region, up to 1.6 m long sediment sequences could be recovered from 5 of the 10 lakes. The sediment sequences will provide crucial information about past environmental changes. The basis of the sediment sequences was mostly formed by minerogenic matter, which was likely deposited during the deglaciation at the end of the last glacial maximum. With the onset of limnic sedimentation, the sediments became enriched in organic matter, thus partially presenting a very fine lamination. The high content of organic matter was somewhat surprising, but can likely be explained by the relatively rich vegetation in the catchments of the lakes. Although the study area is located between 500 and 600 m a.s.l., shrub willows, herbs, and grasses are very abundant. The fine lamination in the limnic sediment sequences most likely reflects long-term and short-term environmental changes. The recovery of sediment sequences from different lakes in the region will enable to distinguish local and regional environmental changes, which is an important precondition for a reliable interpretation of the data. In addition to the work on the lakes, a small team carried out extensive sampling of erratics along several profiles from the ice sheet. The determination of the cosmogenic radiation in these erratics also will provide information on the ice sheet retreat and past glacier movements. Furthermore, a GPS station established at the camp collected important data for the regional isostatic uplift. The data and samples recovered during the fieldwork on land hence will significantly contribute to a more comprehensive picture of the history of deglaciation, climatic and environmental changes during the past ca. 10,000 years, and the stability of the ice sheet.

This week the weather has been perfect for our planned flight activities. Despite low temperature the flight weather on September 12th was excellent. This allowed us to recover the last three GPS stations, which were placed on the mainland of Greenland.

Best wishes to the readers at home

Wilfried Jokat, September 13th, 2009
Jan Mayen Fracture Zone     +1°C          72°00’N  016°00’W