The spatiotemporal patterns of sea ice in the Bohai Sea during the winter seasons of 2000–2016

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ABSTRACTIn this study, sea ice thickness (SIT) and sea ice extent (SIE) in the Bohai Sea from 2000 to 2016 were investigated. A surface heat balance equation was applied to calculate SIT using ice surface temperatures estimated from the Moderate Resolution Imaging Spectroradiometer (MODIS) data with input from air temperature and wind speed from reanalyzing weather data. No trend was found in SIT during 2000–2016. The mean SIT and SIE during this period were 5.58±0.86 cm and 23×103±8×103 km2, respectively. The largest SIT and SIE periods were observed during the second half of January and the first half of February, respectively. The Spearman correlation coefficient between mean ice thickness and average air temperature from 21 automatic weather stations around the Bohai Sea was –0.94 (P < .005), and the coefficient between median ice extent and negative accumulated temperature was –0.503 (P < .001). The rate of increase in air temperature around the Bohai Sea is 0.271°C per decade in winter for 1979–2016 (P < .05), which is much lower than that in northern polar area (0.648°C per decade). This rate has not resulted in a decreasing trend in SIT and SIE for the past 16 years in the Bohai Sea.