Increase in the wave power caused by decreasing sea ice over the Sea of Okhotsk in winter

Abstract

AbstractIncreasing ocean surface waves owing to decreasing sea ice in the Sea of Okhotsk (SO) is a major concern. However, long-term trends of ocean surface waves in the SO have not yet been investigated. Therefore, the long-term trends of wave power ($${P}_{\mathrm{w}}$$ P w ) in the SO were investigated using the 40-year (from the 1980s) simulations and based on the wave model (WAVEWATCH III) enforced by three reanalyses and one satellite product. Three wave model simulations were conducted using the original (hourly or daily) reanalysis or satellite sea ice data. In addition, to quantify the responses of the long-term $${P}_{\mathrm{w}}$$ P w trends to surface winds and sea ice, three wave model simulations were performed with climatological sea ice data, for a total of six model simulations. The model results of the original sea ice data corresponded well with the buoy observations. Moreover, $${P}_{\mathrm{w}}$$ P w increased (~ 12–15% per decade) remarkably during winter (December–February). The increased $${P}_{\mathrm{w}}$$ P w could be attributed to the strengthened surface winds and reduced sea ice (i.e., reduction of direct wave decay by sea ice). Moreover, a horizontal gradient of sea level pressure enhanced by the reduced sea ice strengthened the surface winds. These results suggested that the reduction of sea ice is the most important factor responsible for the positive $${P}_{\mathrm{w}}$$ P w trend over the SO during winter.