Arctic Sea Ice Melt Onset Timing From Passive Microwave‐Based and Surface Air Temperature‐Based Methods

Abstract

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.

Regional variability of Arctic sea ice seasonal change climate indicators from a passive microwave climate data record

“…The regional boundaries in this work are similar to those used in many other studies (e.g. Meier et al 2007, Peng and Meier 2017, Bliss and Anderson 2018. It should be noted that local forcing on the dates at scales smaller than the regions used here warrant further investigation (e.g.…”

“…Arctic sea ice is now more susceptible to earlier melt onset (MO) (e.g. Mortin et al 2016, Bliss andAnderson 2018), more extensive summer retreat (e.g. Meier et al 2007, Cavalieri andParkinson 2012), delayed autumn freeze-up (e.g.…”

Passive Microwave Melt Onset Retrieval Based on a Variable Threshold: Assessment in the Canadian Arctic Archipelago

“…Three Northern Hemisphere polar stereographic grids are available from NSIDC at 25 km, 12.5 km and 6 km nominal grid spacing (NSIDC). For comparison with MO from AHRA and PMW [7,12], MO dates were determined using the 25 km NSIDC grid. An additional set of MO dates were estimated using AMSR2 data on the 6 km grid.…”

“…The appearance of water in the snowpack, indicating the onset of melt, is often correlated with an increase in SAT, where the SAT is taken to be the 2 m air temperature either from an in-situ observation [1,2,25] or from a surface analysis based on a weather forecasting model [26]. In an earlier study [12], AHRA MO dates were compared to those estimated by thresholding SAT using various methods, which we have also adopted here. These methods are as follows: For this comparison both daily and 14 day averaged SAT data were used over a range of SAT thresholds.…”

“…Data from synthetic aperture radars (SARs), scatterometers and passive microwave radiometers have been used in previous studies to determine MO dates [8][9][10][11][12]. While data from both SARs and scatterometers can yield MO dates at reasonably high spatial resolution (100 m-5 km), the most commonly used MO retrieval methods use passive microwave data from the scanning multi-channel microwave radiometer (SMMR), and/or the special sensor microwave/imager (SSM/I), or the special sensor microwave imager/sounder (SSMIS).…”