Abstract
Using the high-resolution global ocean-sea ice model MITgcm-ECCO2, variability and changes of Arctic sea ice export through Fram Strait during 1979–2012 are examined. The simulated annual mean ice export is about 3216 km3/year, which is 12.7% of the 34-year averaged Arctic sea ice volume, with the maximum and minimum occurring in 1994/95 and 1984/1985, respectively. Winter (October–March) ice export is much more than summer (April–September) and exhibits a greater interannual variation. This study suggests that a significant regime shift of Fram Strait ice export from high to low value occurs around the mid-1990s. Further analysis shows that the regime shift of the atmospheric circulation from conventional Arctic Oscillation/North Atlantic Oscillation (AO/NAO) to the dipole-structure Arctic Rapid change Pattern (ARP) plays an important role on the regime shift of ice export. This shift of atmospheric circulation pattern dominates the variability of ice motion and changes the main source region of ice outflow. Combined with the decreased ice thickness and the less ice outflow related to the weakened northerly/northeasterly winds near the strait, sea ice export decreased, eventually generating a regime shift around the mid-1990s. The distinct impact of changes in Fram Strait ice export on the Arctic sea ice inside the basin before and after mid-1990s indicates that the recent continuing loss of Arctic sea ice was mainly induced by the accelerated ice melting in the Arctic Ocean, rather than the ice outflow through Fram Strait.
Highlights
The Arctic sea ice extent (Comiso 2012; Cavalieri and Parkinson 2012) and thickness (Rothrock et al 2008; Kwok et al 2009; Kwok and Rothrock 2009; Laxon et al 2013; Lindsay and Schweiger 2015) have significantly decreased during the recent decades
The increase in Fram Strait sea ice export identified for the time period from the late 1980s to the mid1990s has been well examined, and is suggested to be driven by the changes of atmospheric circulation associated with the positive polarity of Arctic Oscillation (AO) or North Atlantic Oscillation (NAO) (Fig. 10)
Following the dramatic circulation pattern shift, two scientific questions arise: how does Fram Strait sea ice export change since mid-1990s and what contribution does the changing Fram Strait sea ice export have to the accelerated sea ice decline in the Arctic Ocean in different time periods? These two questions will be addressed in this paper through a modeling study by using a coupled ocean-sea ice model
Summary
The Arctic sea ice (especially multiyear ice) extent (Comiso 2012; Cavalieri and Parkinson 2012) and thickness (Rothrock et al 2008; Kwok et al 2009; Kwok and Rothrock 2009; Laxon et al 2013; Lindsay and Schweiger 2015) have significantly decreased during the recent decades. The increase in Fram Strait sea ice export identified for the time period from the late 1980s to the mid1990s has been well examined, and is suggested to be driven by the changes of atmospheric circulation associated with the positive polarity of AO or North Atlantic Oscillation (NAO) (Fig. 10). It was suggested in previous studies that positively polarized AO could largely increase Fram Strait ice volume export (e.g., Zhang et al 2003; Kwok et al 2004, 2013; Kwok 2009) through the anomalous atmospheric circulation pattern Most of these studies have focused on this time period (from the late 1970s or late 1980s to the mid-1990s), while little study discussed the possible mechanisms of the ice export variability since . Following the dramatic circulation pattern shift, two scientific questions arise: how does Fram Strait sea ice export change since mid-1990s and what contribution does the changing Fram Strait sea ice export have to the accelerated sea ice decline in the Arctic Ocean in different time periods? These two questions will be addressed in this paper through a modeling study by using a coupled ocean-sea ice model
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