North Pacific Eastern Subtropical Mode Water simulation and future projection
- PDF / 602,865 Bytes
- 6 Pages / 595.276 x 841.89 pts (A4) Page_size
- 26 Downloads / 189 Views
North Pacific Eastern Subtropical Mode Water simulation and future projection XIA Ruibin1, LIU Qinyu1*, XU Lixiao1, LU Yiqun1 1
Physical Oceanography Laboratory/Qingdao Collaborative Innovation Center of Marine Science and Technology, Key Laboratory of Ocean-Atmosphere Interaction and Climate in Universities of Shandong, Ocean University of China, Qingdao 266100, China
Received 11 June 2014; accepted 18 December 2014 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2015
Abstract The present climate simulation and future projection of the Eastern Subtropical Mode Water (ESTMW) in the North Pacific are investigated based on the Geophysical Fluid Dynamics Laboratory Earth System Model (GFDL-ESM2M). Spatial patterns of the mixed layer depth (MLD) in the eastern subtropical North Pacific and the ESTMW are well simulated using this model. Compared with historical simulation, the ESTMW is produced at lighter isopycnal surfaces and its total volume is decreased in the RCP8.5 runs, because the subduction rate of the ESTMW decreases by 0.82×10−6 m/s during February–March. In addition, it is found that the lateral induction decreasing is approximately four times more than the Ekman pumping, and thus it plays a dominant role in the decreased subduction rate associated with global warming. Moreover, the MLD during February–March is banded shoaling in response to global warming, extending northeastward from the east of the Hawaii Islands (20°N, 155°W) to the west coast of North America (30°N, 125°W), with a maximum shoaling of 50 m, and then leads to the lateral induction reduction. Meanwhile, the increased northeastward surface warm current to the east of Hawaii helps strengthen of the local upper ocean stratification and induces the banded shoaling MLD under warmer climate. This new finding indicates that the ocean surface currents play an important role in the response of the MLD and the ESTMW to global warming. Key words: eastern subtropical mode water, global warming, mixed layer depth, subduction rate, heat advection Citation: Xia Ruibin, Liu Qinyu, Xu Lixiao, Lu Yiqun. 2015. North Pacific Eastern Subtropical Mode Water simulation and future projection. Acta Oceanologica Sinica, 34(3): 25–30, doi: 10.1007/s13131-015-0630-y
1 Introduction In the subtropical gyres and parts of the subpolar gyres of the global oceans, there are distinct water masses characterized by a nearly vertically homogeneous layer of low potential vorticity (PV) lying just above or within the permanent pycnocline. These water masses, known as “mode waters”, enter the permanent pycnocline and are advected to spread over a much wider area, carrying temperature, salinity, and PV anomalies. The formation, circulation, and dissipation of mode waters and their variability are related to ocean-atmosphere interaction and various upper-ocean dynamic and thermodynamic processes over a wide range of time scales (Hanawa and Talley, 2001; Oka and Qiu, 2011). There are three types of mode waters in the North Pacific subtropical gyre: the
Data Loading...
