Arctic Sea Ice Melt Onset Timing From Passive Microwave‐Based and Surface Air Temperature‐Based Methods
Melt onset (MO) on Arctic sea ice has been monitored using satellite‐based passive microwave (PMW) observations since 1979. In this work, surface air temperatures from the International Arctic Buoy Programme/Polar Exchange at the Sea Surface and NASA's Atmospheric Infrared Sounder are used to derive MO date estimates using three threshold methods which are then compared with a record of PMW‐based MO dates. Results from the PMW data indicate a shift toward increasingly early MO timing, with significant trends as large as −9.45 days/decade in the E. Siberian Sea and −5.69 days/decade for the entire Arctic, consistent with other studies highlighting the overall decline of Arctic sea ice. Results indicate that the surface air temperature‐based MO date estimates produced using a −1 °C threshold are ~11 days later than the PMW‐based MO date estimates Arctic wide. A statistical comparison of the Polar Exchange at the Sea Surface and PMW‐based MO dates indicate that despite the ~11‐day bias, correlations between the MO date time series are generally good (≥0.6) for most of the Arctic Ocean while the Atmospheric Infrared Sounder and PMW‐based MO dates are generally better at capturing the statistically similar long‐term trends in MO dates for the Arctic and several Arctic subregions. Application of these results can contribute to the development of new methods to monitor the sea ice melting state.