Abstract
As Arctic sea ice melts, cyclones potentially enhance the mechanical and thermodynamic forces that influence the vulnerable ice edge. However, examples can be found in satellite observations and reanalyses where cyclones either locally increase or decrease ice within the marginal ice zone (MIZ). Two case studies with these opposing ice responses are presented. Guided by the tendencies during these events, 264 strong (minimum surface pressure below 984 hPa) summer cyclones were sorted by prevailing wind direction and sea surface temperature (SST) changes within the MIZ to quantify the net ice impacts in the present-day Arctic (2010–19) and early satellite era (1982–91). By tracking the MIZ ice area from 1 week before the cyclone’s formation through 2 weeks after, we find cyclones that enhance southerly winds mostly decrease the ice area, whereas enhanced northerlies generally increase the ice area within the MIZ later in the season. Furthermore, early summer storms tend to decrease the MIZ ice area more than late summer storms. A shift toward more frequent early summer storms is observed from the 1980s to the 2010s, resulting in almost two-thirds of recent storms decreasing area. Consequently, recent summer cyclones have more negative impacts, resulting in a decline of more than 40 000 km2 of MIZ ice area on average, whereas 1980s cyclones had little aggregate impact. Wind direction and SST trends partially reconcile the wide range of MIZ ice area changes due to cyclone passage, yet considerable variations in individual cyclones’ impacts remain even when controlling for these factors. These bulk diagnostics therefore only explain part of the complex ice–cyclone relationship.
Significance Statement
The purpose of this study is to better understand how intense summer storms in the Arctic impact the underlying, low-concentration sea ice around the ice edge (where the ice is most vulnerable to external changes). Both enhanced decreases and increases in ice area within this region over the lifetime of a storm were observed, with late summer impacts dominated by differences in mean wind direction over the sea ice. Overall, storms earlier in the summer season were found to decrease ice area more than storms later in the season. We also found a shift in the distribution of storms to earlier in the summer when comparing the 1980s–2010s, causing more negative effects from cyclones overall in recent years.
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