Abstract
ABSTRACTIn Northeast Greenland, the Norske Øer Ice Barrier (NØIB) abuts Nioghalvfjerdsfjorden (79N) and Zachariae Isstrøm (ZI), two floating outlets of the Northeast Greenland Ice Stream. NØIB is an extensive region of perennially fast sea ice, which varies in size from year to year, but with complete breakup a rare event in the 20th century. It reportedly broke up in the 1950s and was seen to break up in 1997. Since 2000 the NØIB has broken up during 11 of the last 14 summers. The forcings driving the increased frequency of ice barrier breakup are poorly understood, and it is not clear if the breakup is a purely local phenomenon or an indicator of regional changes in the ocean and atmosphere. Here we use a logistic regression statistical model to show that the odds of breakup are linked to June positive degree days and July wind speeds at a nearby weather station. It is too soon to know if subtle changes detected on 79N and ZI in the last decade are connected to breakups of the NØIB but, if they are, it suggests a complex interaction between the atmosphere, ocean and outlet glaciers in this part of Greenland.
Highlights
Sea ice can potentially exert an important control on the behavior of Greenland’s outlet glaciers (Reeh and others, 2001)
We have shown that the Norske Øer Ice Barrier (NØIB) has broken up during the summers of 2001–2005, 2008, and 2010–2014
A logisitic regression model shows that the odds of breakup are strongly linked to the June positive degree days (PDDs) and July winds as recorded at nearby weather stations
Summary
Sea ice can potentially exert an important control on the behavior of Greenland’s outlet glaciers (Reeh and others, 2001). In the summer of 1933, Lauge Koch made a number of flights over northeast Greenland from a ship anchored off Norske Øer and noted a 100 km stretch of open water between Nordöstrundingen, Greenland’s most northeasterly cape and 79N He suggested that the open water existed because it was sheltered from the sea ice exiting through the Fram Strait and flowing southward (Koch, 1935). This hypothesis was supported and refined almost 60 years later by Schneider and Budéus (1994) based on data collected during a 1991 cruise and a follow-up study in the spring and summer of 1993 They proposed that two ice barriers, one along the Ob Bank southeast of Nordöstrundingen and another centered on Norske Øer, the NØIB, were major factors in the creation and the persistence of the NEW polynya. We consider the possible contributions of changing ice thickness, surface meltwater and the warming of the waters flowing beneath the ice barrier to break up
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