Delayed Chukchi Sea Ice Advance by the Anomalous Warm SST in November 2018
The sea ice advance around the wider Chukchi Sea area was also examined by the AMSR satellite measurements. The sea ice concentration (SIC) in November 2018 is significantly smaller than the mean over 2002-2018 and is close to the 25 percentile. In Fall 2018, the slowdown of the sea ice advance is remarkable from Nov. 14th and Nov 30th. Overall, there was a three week delay in the sea ice advance. This delay is not related to the air-sea heat flux. The atmospheric condition was indeed favorable for freezing with a large negative heat flux. Undoubtedly, the sea ice advance is compensated by the warm Chukchi Sea water.
The interannual variation of the November SST in the Bering and Chukchi Seas is found to be highly correlated with the annual Pacific Decadal Oscillation (PDO) index. The high correlation indicates PDO is potentially influential on the interannual variation of the Chukchi Sea SST. It should not be however the factor of the high SST found in November 2018 because the PDO index is close to zero in 2018. The warm SST over the Chukchi Sea in November 2018 seems preconditioned by the unusual wind pattern in September 2018. With the southerly wind driven transport, a large amount of heat is likely injected to the Chukchi Sea. Based on the atmospheric reanalyses, the air-sea surface heat flux was also increased although the influence was smaller.