Study On Global Ocean Wave Long-term Trends And The Northwest Pacific Ocean Wave Characteristics

As a key physical phenomena in the air-sea interface,ocean surface waves play an important role in the global climate system.In this paper,the ERA-20C historical reanalysis data and the prediction results of climate model FIO-ESMv2.0 based on the latest CMIP6 scenario are used to analyze the global long-term trend of significant wave height?H_s?and 99th percentile significant wave height(H_max)in the past 100 years and future.Using the same datebase and EOF analysis method,the characteristics of H_s spatio-temporal variations in the Northwest Pacific Ocean over past 100 years are analyzed,the relationships between the long-term ocean surface waves and the atmospheric factors are investigated.The main conclusions are as follows:Over the past 100 years?1911-2010?,the global H_sshows generally increasing trend,the linear trend of the annual average H_sis 1.0%/10a?global mean result?.The change of H_shas significant spatial differences,and the most significant increasing trend is located in the mid and high latitude areas?30°N-60°N?of northern hemisphere,and H_s in the Southern Ocean also shows clear increasing trend.The annual average H_sin the South Pacific Ocean does not change much,while it shows a significant decreasing trend in winter.Global H_max?99th?over the past 100 years mainly shows an increasing trend in the northern hemisphere and a decreasing trend in the southern hemisphere.In the 21^st century,global H_s,especially H_max,shows decreasing trend,while H_s and H_max in the mid and high latitudes of the Southern Ocean seas show increasing trend.Under the future emission scenarios of SSP245and SSP585,the linear trends of the annual average H_maxfrom 2001 to 2100are-0.5%/10a and-1.0%/10a?global mean results?,respectively.No matter in the past or future,H_s and H_max in the Northwest Pacific shows significant changing trend with obvious seasonal differences.Futher studies on the characteristics of the spatial and temporal changes of H_sover the past 100 years show that EOF1 in summer and winter mainly exhibit consistently increasing or decreasing pattern in the Northwest Pacific Ocean.The change of H_s in summer is related to the East Asian Summer Monsoon?EASM?,when EASM is strong,10m wind has southwesterly anomaly,resulting in the increase of H_s,and vice versa.The change of H_s in winter is related to the Aleutian low?AL?,when AL is strong,10m wind has southwesterly anomaly in the subtropical Northwest Pacific,resulting in the increase of H_s,and vice versa.The EOF2 pattern in summer shows the out-of-phase distributions in high and low latitudes,with 20°N as a boundary,which is related to the Arctic Oscillation?AO?.The EOF2 pattern in winter showsthe out-of-phase distributions that H_s increase/decrease in the west and decrease/increase in the east bounded by 150°E,with the significant inter-annual variation,and which is related to the changeof the East Asian Winter Monsoon?EAWM?.The EOF3 pattern in summer shows the out-of-phase distributions that H_s decrease/increase in the west and increase/decrease in the east bounded by 140°E.The EOF3 pattern in summer shows the out-of-phase distributions that H_s increase/decrease at high latitudes and decrease/increase at low latitudes north of 20°N,and H_s decrease/increase in the west and increase/decrease in the southeast of 20°N.There exists decadal oscillations in both summer and winter H_s changes,and the decadal oscillation in winter is related to the Pacific Decadal Oscillation?PDO?.