Pacific Northwest Sea-level Change And Its Impact Factors

Along with the climate change research gradually thorough, synthetically study on influence factors's contribution in various time scales will be strengthen. In this paper, we analyse the Sea level, Steric sea level, wind stress curl and Freshwater flux using Empirical Orthogonal Functions (EOF). The result are that Kuroshio Extension (KE), North Pacific warm pool and the South China Sea are the core change region for the spatial distribution of EOF, and the interannual cycles are existed(according to the temporal eigenfunction). Thus we focus on these three regions, analyzing the interannual sea level variation and its influencing factors.On interannual and interdecadal time scale, TSea level and Steric sea level show evident variations, and have a better consistency in the upstream of KE. However, in the downstream region, Sea level variation obviously in interdecal time scale, and Steric sea level changes obviously in interannual time scale. The vertical structure of the temperature is the main reason for the interannual variations of Steric sea level. Down below 200m, the temperature has an obvious interannual characters. Wind field has a significant effect on the interannual sea level changes in KE. In the upstream region, the correlation coefficient between the anomaly of wind stress curl and T/P sea level is-0.5. Wind stress curl decreases, then sea level rises, and vice versa. But, in the downstream, it has a worse correlation. Freshwater's change range is smaller than the sea level', and has little impact on the sea level.Sea level and Steric sea level have a correlation with ENSO event. Steric effects is the main reason for Sea level's interannual variation in warm pool. Ocean water changes greatly in 100m-300m below sea surface. Wind filed effect on interannual sea level significantly. Walker circulation impacts on warm pool's interannual sea level. Freshwater flux have a positive contribution on sea level interannual variation. Precipitaion impact on sea level more than evaporation. ENSO events impact on interannual sea level variation in the South China Sea. Steric effects is the main reason for sea level's interannual variation. Vertical structure of temperature do not significantly correlation with ENSO. Wind stress curl have a positive correlation coefficient with sea level variation. When El Nino events occurrence, Walker circulation and Hardley circulation impacts on sea level's interannual variation. Freshwater flux have a positive contribution on the South China Sea's interannual sea level variation.