Statistical Analysis of Arctic Cyclone Influence on Sea Ice Concentration (SIC) and Extent (SIE)

Climate change is causing the Arctic to warm four times faster than the global average, a phenomenon known as Arctic Amplification (AA) (Rantanen et al. 2022). There are several important positive feedback mechanisms that contribute to AA. One such mechanism is the ice-albedo feedback. Due to positive feedback loops, it is important to better project sea ice concentration (SIC) and extent (SIE). One synoptic-scale contributor to SIC/SIE is the Arctic cyclone (AC). There is currently significant debate on whether ACs lead to SIC/SIE gain or loss (e.g., Rae et al. 2017; Semenov et al. 2019; Schreiber and Serreze 2020). For this reason, this paper analyzes the impacts of ACs on SIC/SIE using the Community Earth System Model Large Ensemble (CESM-LE).

The main AC metrics investigated in this study were cyclonic vorticity () and maximum Arctic pressure gradient (PG). Such metrics were correlated to a running-average change (RAC) in SIE anomaly between the CESM-LE mean and an ensemble member of interest (EMI). A strong correlation between either AC variable was not established. There was, however, a strong correlation between maximum PG and a RAC in SIE anomaly in the marginal ice zone with low SIC. This suggests that significant sea ice loss is expected where SIC is sufficiently low due to mechanical transport of the sea ice out of the Arctic and warm air advection associated with ACs. Our findings, however, also reveal that an important sea ice loss mechanism fostered by ACs is not present in the CESM-LE. A strong PG generates strong winds and thus large ocean waves. Such waves break apart sufficiently thin sea ice (Blanchard-Wrigglesworth et al. 2022). In more central Polar regions where a strong correlation due to low SIC is expected, a low correlation is observed. This important finding signifies that reparameterization of ocean waves within the CESM-LE is necessary for more accurate sea ice projections under AA.