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

ABSTRACT

In 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.

KEYWORDS:

• Sea ice
• the Bohai Sea
• global warming
• ice thickness
• ice extent

Acknowledgements

The authors are grateful to NASA’s Level-1 and Atmosphere Archive & Distribution System (LAADS) Distributed Active Archive Center (DAAC) for providing daily MODIS imagery of the Bohai Sea, the European Centre for Medium-Range Weather Forecasts (ECMWF) for providing ERA-Interim reanalysis data including wind speed and air temperature, and the Climatic Data Center of the National Meteorological Information Center at the China Meteorological Administration for providing daily air temperature from 21 automatic weather stations around the Bohai Sea. Last but not least, the authors wish to thank the anonymous reviewers who did a thorough critical review of the manuscript and provided valuable suggestions to improve it.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Chinese Arctic and Antarctic Administration, National Natural Science Foundation of China (Grant Nos. 41676176, 41676182 and 41428603), and Chinese Polar Environment Comprehensive Investigation and Assessment Program.