Ocean driven melting of Northeast Greenland’s major glaciers
5-1.214 - Linke Seite – Großer, unterteilbarer Konferenzraum
GEOMAR - Standort Ostufer / GEOMAR - East Shore
Speaker: Dr. Claudia Wekerle, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Germany
Hybrid - online via https://geomar.webex.com/geomar-en/j.php?MTID=mf415834ed76a742bacf01eada863885d
Meeting number: 2787 635 2083
Password: XYwu583sQtA
Abstract
As the Arctic warms four times faster than the global average, the Greenland Ice Sheet is losing mass at an accelerating rate. About 25% of the current global mean sea-level rise is caused by the mass loss of the Greenland Ice Sheet, with a substantial increase in recent decades. The ice sheet’s mass loss comprises surface meltwater runoff, calving of marine-terminating glaciers, frontal melting of tidewater glaciers, and basal melting of ice tongues. Most of the mass loss thus occurs at the interface where glaciers meet the ocean. In this talk, I will focus on two glaciers located in Northeast Greenland, the 79N Glacier (79NG) and the Zachariæ Isstrøm (ZI). The 79NG features a floating ice tongue which has seen sustained thinning in recent years. Nonetheless, it’s extent has been relatively stable. In contrast, the ZI’s ice tongue almost disappeared in the last decades, it thus turned into a tidewater glacier. Based on simulations with the high-resolution sea ice/ice shelf/ocean model FESOM2, we could show that the interannual variability of basal melt below 79NG over the past 50 years is mainly associated with changes in the temperature of the Atlantic Intermediate Water (AIW) inflow. However, contrary to this long-term ocean warming trend, mooring observations at the calving front of 79NG revealed a distinct cooling of AIW temperatures from 2018 to 2021, and reduction in basal melting. The signature of the colder AIW temperatures can be traced back to eastern Fram Strait, where this cooling represents the largest event since continuous observations were initiated in 1997, and further upstream, connected to the slowdown of the large-scale ocean circulation in the Nordic Seas. We attribute this regional ocean cooling to a pattern of European atmospheric blocking that intensifies the export of cold air from the central Arctic Ocean through Fram Strait, impeding the northward flow of ocean heat. This pronounced atmospheric blocking appears to be the driver of major AW cooling events over the last 50 years, and will remain an important driver of multi-annual ocean cooling affecting Northeast Greenland’s glaciers.