Mechanisms for the formation and variability of the Kuroshio Extension system and its influences on the atmosphere and the marine ecosystem
| A02-5. Mechanisms for the formation and variability of the Kuroshio Extension system and its influences on the atmosphere and the marine ecosystem | |
|---|---|
| PI | Masami NONAKA * (Team leader, JAMSTEC) |
| Members | Atsushi KUBOKAWA* (Prof., Hokkaido Univ.), Hideharu SASAKI* (Sub leader, JAMSTEC), Bunmei TAGUCHI* (Researcher, JAMSTEC), Shigeki HOSODA* (Deputy team leader, JAMSTEC), Hideyuki NAKANO* (Senior researcher, MRI) |
| Adjunct members | Norihisa USUI* (Researcher, MRI), Hiroyuki TSUJINO* (Senior researcher, MRI), Yoshikazu SASAI* (Senior researcher, JAMSTEC), Kosei SASAOKA% (Assistant researcher, JAMSTEC), Ichiro YASUDA* (Prof., Univ. Tokyo) |
| PD | Kunihiro AOKI* (Hokkaido Univ.) |
JAMSTEC: Japan Agency for Marine-Earth Science and Technology
MRI: Meteorological Research Institute, Japan Meteorological Agency
[Doctral degree/Field: *Oceanography, %Fisheries]
Strong jets of Kuroshio, Oyashio and their extensions are associated with strong contrast of ocean temperature across them. It has been suggested that variability in these oceanic temperature frontal zones induce significant variability in sea surface temperature (SST) and/or heat release from the ocean and can exert feedbacks to the atmosphere. Furthermore, resultant atmospheric variability may affect oceanic circulation, inducing and/or maintaining decadal time scale variability over the North Pacific. Also, variability in the oceanic frontal zones is expected to have significant impact on oceanic ecosystem. However, many mechanisms included in these processes are still unknown, and we aim to clarify them. More specifically, we are investigating following themes, closely collaborating with other programs.
- (i) Dynamical mechanisms to determine axial latitude and zonal length of the mean Kuroshio Extension (KE) jet, strength of the associated recirculation gyres to the south and north, and their decadal time scale variability. For this purpose, we are analyzing output data from decades long integrations of eddy resolving ocean general circulation models, and/or an ocean data assimilation/prediction system, focusing on non-linear responses of ocean eddies and strong jets.
Also, we are going to conduct ensemble experiments using an eddy resolving ocean model combining with an oceanic ecosystem model. By integrating the model from slightly different initial conditions, we will investigate intrinsic variability in oceanic eddies and jets, and their impacts on nutrient and phyto- and zoo-plankton fields. Also, we will utilize satellite observed data to compare and compensate the simulation data. - (ii) Variability in meridional SST contrast across the KE front and heat/water vapor release from the ocean due to variability in the KE jet, and their impacts on activities of storms aloft, the Baiu front, and East Asian summer monsoon. We will utilize high-resolution ocean-atmosphere coupled model simulations, and in situ observed data including that obtained by sea surface buoys. Also, we explore influences of local air-sea interaction over the KE region upon the basin scale atmospheric circulation over the North Pacific, and any possibility that such atmospheric responses can further affect the ocean circulation, and oceanic frontal zones. [Collaboration with A03-7, A03-8, and A02-4 programs.]
In the open ocean, rather than the oceanic frontal zones, variability in oceanic temperature is generally governed by atmospheric thermal forcing. Then, heat content of the oceanic surface layer is crucial for air-sea interaction, and we aim to clarify its spatio-temporal variability based on in situ vertical profile data obtained by the automatic observation (Argo float) system, collaborating with A02-4 & A02-6 programs.
