Sea ice variability along the Okhotsk coast of Hokkaido based on long-term JMA meteorological observatory data

Long-term sea ice observation data at the Japan Meteorological Agency observatories along the Okhotsk coast of Hokkaido were analyzed. The observations at the Abashiri Local Meteorological Observatory largely explained the variations at other sites along much of the Okhotsk coast on a time scale longer than a few days. Interannually, variations of the maximum sea ice areas in the whole and southern Sea of Okhotsk were largely reflected in the yearly accumulated sea ice concentration (SIC) and sea ice duration variations at the observatories. A comparison with several indices for the North Pacific climate variability suggested that the North Pacific Index (NPI) is a robust indicator of the recent (after the 1980s) sea ice variations in the Sea of Okhotsk on a decadal time scale. Specifically, variations in the first sea ice appearance date at the observatories resulted from variations in the Aleutian Low with meridional wind anomalies over the Sea of Okhotsk and the air temperature around Japan in January; variations in the final disappearance date resulted from the Aleutian Low variations, and the resulting sea ice cover variations in the Sea of Okhotsk except for the Siberian coast affected the air temperatures in April. These factors influenced the sea ice duration. A strong linkage was found between variations in the local sea ice (along the Hokkaido coast) and large-scale fields, which will help improve our understanding of the sea ice extent and retreat variability over the Sea of Okhotsk and its linkage to the North Pacific climate variability.