Characteristics of sea surface temperature and Chlorophyll concentration inside mesoscale eddies in the North Pacific Ocean

Mesoscale eddies are active in the North Pacific Ocean (NPO) sensitive to the global variation of the atmosphere and ocean and directly affect the climate and coastal areas of the country. Therefore, the influence of the mesoscale eddies in the NPO on the marine ecological environment needs to be examined. The relationship between Sea Surface Temperature (SST) and Chlorophyll-a (Chl-a) concentration inside these eddies as well as the response mechanism of these eddies to local ecological processes also warrant further research. In this paper, the Archiving, Validation, and Interpretation of Satellite Oceanographic data (AVISO)-merged satellite altimeter data are used to identify and track 992 mesoscale eddies in the NPO during the years of 2007-2012, including 442 Cyclonic Eddies (CEs) and 550 Anticyclonic Eddies (AEs), in the NPO between 2007 and 2012. The spatial and temporal distributions of the SST and the Chl-a concentration inside these eddies are analyzed via Operational Sea surface Temperature and sea Ice Analysis (OSTIA) SST and MODIS data, and the variability of these parameters inside typical eddies is examined. The results show that the temperature intensity of CEs (ICE) has a higher tendency to demonstrate monthly variations compared with that of AEs (IAE). The seasonal variation of ICE tends to contrast that of IAE. Specifically, ICE shows an obvious annual variation, whereas IAE does not. Stronger ICE and IAE are observed in the Kuroshio Extension intensively. Both CEs and AEs have similar monthly variation tendencies in the temporal and spatial distributions of eddy Chl-a. The annual trends of Chl-a in both AEs and CEs are ambiguous. For AEs and CEs, the highest Chl-a concentration is observed in the high-latitude region. A study of the relationship between the eddy SST and eddy dynamic parameters (e.g., amplitude, vorticity, and Eddy Kinetic Energy (EKE)) reveals that SST inner AEs are either positively or negatively correlated to amplitude with a uniform distribution in space. A negative correlation of SST inner CEs can be observed in the Kuroshio Extension, whereas a positive correlation is observed in offshore areas of California. A positive correlation is more frequently observed in AEs than in CEs. The correlation of SST with vorticity in AEs is either positive or negative, while in CEs, SST shows a negative correlation with vorticity. The correlation of SST with EKE in AEs is either positive or negative, but such correlation is only positive uniquely in CEs. The Chl-a concentration in AEs is positively correlated with amplitude and has a uniform distribution in space. In CEs, Chl-a concentration shows a positive correlation with amplitude in the Kuroshio Extension and in Alaska Bay. Chl-a concentration also shows a positive correlation with vorticity in both AEs and CEs, a positive correlation with EKE in AEs, and either a positive or negative correlation with EKE in CEs. We conclude that SST demonstrates obvious monthly and annual variation tendencies in CEs, and high ICE and IAE values are distributed in the Kuroshio Extension of the NPO. The Chl-a concentration in CEs and AEs demonstrate a similar monthly variation tendency and an ambiguous annual variation. Eddies with a high Chl-a concentration are mainly located in the high-latitude region of the NPO. The relationship between the eddy SST and the eddy dynamic parameters is treated as a local feature of the NPO, and a positive relationship between eddy Chl-a concentration and eddy dynamic parameters is observed in the Kuroshio Extension and Alaska Bay. The influence of mesoscale eddies on the ecological processes is related to the type and eddy lifetime of eddies in the NPO. © 2020, Science Press. All right reserved.