Visualization Of The Thermocline In The Central And Western Pacific

This dissertation mainly studies the distribution characteristics of thermocline in anomalous climate and the effect of its changes on the distribution of fisheries.In this paper,the global ocean Argo grid data set(BOA_Argo)from 2008-2017 and the fishing log data of commercial fishing vessels during the same period were used to study the temporal and spatial characteristics of the thermocline in the main fishing grounds of the yellowfin tuna purse seine in the western and central Pacific Ocean in La Ni?a and El Nino years The GAM(generalized additive model)model was used to analyze the spatiotemporal and environmental variables affecting yellowfin tuna.The results show that(1)The temperature of the upper boundary of the thermocline changes from weak to strong with the El Nino event,and the high-value zone of the temperature shifts eastward,moving closer to 15 ° north and south latitudes of the equator.The upper boundary depth of the central and western Pacific in the range of 0 °-10 ° S is shallower.Taking the 10 ° N latitude line as the axis,there is a shallow band-shaped distribution structure of the thermocline,and as the El Ni?o event goes from weak to strong,the band-shaped distribution becomes more obvious and the depth value decreases.(2)As the La Ni?a event changed from weak to strong,the high-value zone of the upper limit of the western equatorial Pacific spread to the west and deepened.Generally,when the La Nina phenomenon occurs,the thermocline north of the equator is deep,and the thermocline south of the equator is shallow.(3)The central value of the thermocline strength at the east of the equatorial central and western Pacific generally reaches 0.25 ° C / m,and it can reach 0.3 ° C / m during the strong El Ni?o event.The strong central axis is located near the 10 ° N parallel(4)The thickness of the thermocline in the western Pacific warm pool exceeds 200 m,and the thickness of the thermocline near the southeast of 10 ° S and the northeast of 10 ° N is more than 250 m.The thickness of the thermocline in the equatorial central and western Pacific is thick on the west and thin on the east.As the El Ni?o event changes from weak to strong,the thickness of the thermocline tends to become thinner on the east.(5)In the La Ni?a year,the CPUE moved westward as the high-value zone of the upper bound contracted westward,up to 145 ° E,and in the El Ni?o year,moved eastward to 165 ° E.Compared with normal years,the upper boundary depth difference of the thermocline on the east and west sides of the equatorial Pacific is larger than that of the normal year,and the upper boundary depth of 80-130 m is westward.The strength of the thermocline is generally weak in the west and strong in the east.The thickness of the thermocline is based on 15 ° N and 15 ° S axes,and each has a thick bandlike distribution structure.The CPUE is distributed between 120 and 200 m thick.The areas with high abundance of yellowfin tuna resources are 5 °N-5 °S,150 °E-175 °E.The optimal upper temperature range of the thermocline in the fishing place is 27.5-29.5 ℃,the optimal upper depth range is 80-120 m,the thickness is concentrated between 100-200 m,and the intensity is concentrated between 0.08-0.13 ℃ · m-1 Among them,the upper-bound temperature in the environmental factors has the greatest influence on the distribution of catch per unit effort(CPUE).The study found that the eastward shift of El Ni?o annual catch and the westward shift of La Ni?a annual catch shifted with the optimal upper temperature,upper depth,intensity and thickness of the fishing site in the thermocline.