NET ACCUMULATION ON THE GREENLAND ICE SHEET LINKED TO NORTHERN HEMISPHERE SEA ICE EXTENT

Eleven ice cores were collected from 1995 to 1999 at widely distributed locations on the Greenland ice sheet and used to reconstruct historical annual net accumulation over recent centuries. Each core was analyzed with high depth resolution for a number seasonally varying chemical species and isotopes, providing near zero uncertainty in dating the annual accumulation records. These records demonstrate that net accumulation is highly variable, with dominant periods of temporal variability different for different regions of the ice sheet. To examine the relationship between hemispheric scale sea ice extent and net accumulation in different regions of the Greenland ice sheet, we compared net annual accumulation at each ice core site with principal components derived from anomalies in northern hemisphere sea ice extent over the past century. Results show that variations in accumulation in specific regions of the ice sheet closely match large-scale variations in sea ice extent. For example, decreases in net accumulation in southeast Greenland coincide with increases in sea ice extent in the Greenland and Barents Seas and decreases in sea ice extent in Davis Strait and the Chukchi and Beaufort Seas. Meanwhile, increases in net accumulation in southwest Greenland correlate with decreases in sea ice extent in the Davis and Denmark Straits and the Greenland Sea but increased sea ice extent in the Barent and Laptev Seas. Accumulation near the summit of the Greenland ice sheet where the GISP2 and GRIP bedrock cores were drilled is relatively insensitive to large-scale sea ice extent. The observed strong relationships in variability of net accumulation and hemispheric scale sea ice extent suggest that an array of appropriately located century to millennial scale ice cores in Greenland offers the possibility of reconstructing proxies of annual sea ice extent to place the modern record in long term perspective.