Sea ice measurements during POLARSTERN cruise ANT-XXIII/7 (Winter Weddell Outflow Study)

Various physical properties of snow and sea ice were measured during ice stations in the Western Weddell Sea, Antarctic, during the POLARSTERN cruise ANT-XXIII/7 (WWOS) in 2006. Most stations were reached via a gangway directly from the vessels others by helicopter. All vertical positions are corrected to freeboard, e.g. z=0 represents the snow-ice interface. More detailed information about the data sets and methods are available from the cruise report (section 4 sea-ice physics).

Mean sand flux in cores ER11, ER07 and ER13, Sermilik Fjord, Greenland

During the early 2000s the Greenland Ice Sheet experienced the largest ice-mass loss of the instrumental record, largely as a result of the acceleration, thinning and retreat of large outlet glaciers in West and southeast Greenland. The quasi-simultaneous change in the glaciers suggests a common climate forcing. Increasing air and ocean temperatures have been indicated as potential triggers. Here, we present a record of calving activity of Helheim Glacier, East Greenland, that extends back to about AD 1890, based on an analysis of sedimentary deposits from Sermilik Fjord, where Helheim Glacier terminates. Specifically, we use the annual deposition of and grains as a proxy for iceberg discharge. Our record reveals large fluctuations in calving rates, but the present high rate was reproduced only in the 1930s. A comparison with climate indices indicates that high calving activity coincides with a relatively strong influence of Atlantic water and a lower influence of polar water on the shelf off Greenland, as well as with warm summers and the negative phase of the North Atlantic Oscillation. Our analysis provides evidence that Helheim Glacier responds to short-term fluctuations of large-scale oceanic and atmospheric conditions, on timescales of 3-10 years.