Meridional transport of the North Pacific Intermediate Water in the Kuroshio-Oyashio Interfrontal Zone

North Pacific Intermediate water (NPIW) is a dominant water mass controlling ~400-1200m depth North Pacific Ocean, characterized by its low salinities and relatively lower temperatures. In the modern climate, the interplay between NPIW-related physical and biogeochemical processes among seasons determines annual-mean budget and efficiency of carbon sink into the North Pacific Ocean. Thus, to understand the NPIW physics is key to project roles of the North Pacific Ocean in changing Earth climate and carbon systems in the future. In this study, we provide a modelling view of the NPIW history since Yr 1850 (historical experiment) and its projection to near future (IPCC-defined RCP 4.2 and 8.5 experiments until Yr 2100), using new-generation Alfred Wegener Institute Earth System Model (AWI-ESM). Our results suggest an important role of regional hydroclimate feedback over the NW Pacific and Sea of Okhotsk in determining the NPIW from recent past to near future.

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Roles of the Okhotsk Sea and Gulf of Alaska in forming the North Pacific Intermediate Water

Journal of Geophysical Research Atmospheres ◽

10.1029/1999jc900304 ◽

2000 ◽

Vol 105 (C2) ◽

pp. 3253-3280 ◽

Cited By ~ 66

Author(s):

Yuzhu You ◽

Nobuo Suginohara ◽

Masao Fukasawa ◽

Ichiro Yasuda ◽

Ikuo Kaneko ◽

...

Keyword(s):

North Pacific ◽

Gulf Of Alaska ◽

Intermediate Water ◽

Okhotsk Sea ◽

North Pacific Intermediate Water ◽

The North ◽

The North Pacific

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Persistent millennial-scale links between North Pacific intermediate-water ventilation and North Atlantic Climate during the deglaciation and last glaciation

10.5194/egusphere-egu2020-7221 ◽

2020 ◽

Author(s):

Jianjun Zou ◽

Xuefa Shi ◽

Aimei Zhu ◽

Yuan-Pin Chang ◽

Min-Te Chen ◽

...

Keyword(s):

North Atlantic ◽

North Pacific ◽

North Pacific Ocean ◽

Meridional Overturning Circulation ◽

Intermediate Water ◽

North Pacific Intermediate Water ◽

The North ◽

Last Glaciation ◽

The North Pacific ◽

Millennial Scale

The deep ocean carbon cycle, especially carbon sequestration and outgassing, is one of the mechanisms to explain variations in atmospheric CO2 concentrations on millennial and orbital timescales. However, the potential role of subtropical North Pacific subsurface waters in modulating atmospheric CO2 levels on millennial timescales is poorly constrained. Here, we investigate a suite of geochemical proxies in a sediment core from the northern and middle Okinawa Trough to understand variations in intermediate-water ventilation of the subtropical North Pacific over the last 50,000 years (50 ka). Our results suggest that enhanced mid-depth western subtropical North Pacific (WSTNP) sedimentary oxygenation occurred during cold intervals during the last deglaciation and last glaciation, while oxygenation decreased during the B&#246;lling-Aller&#246;d (B/A) and warm interstadials. The enhanced oxygenation during cold spells is linked to the intensified North Pacific Intermediate Water (NPIW), while interglacial increase after 8.5 ka is linked to an intensification of the Kuroshio Current due to strengthened northeast trade winds over the tropics. The enhanced formation of NPIW during Heinrich Stadials was likely driven by the perturbation of sea ice formation and sea surface salinity oscillations in high-latitude North Pacific. The diminished sedimentary oxygenation during the B/A and interstadials due to decreased NPIW formation and enhanced export production, indicates an expansion of oxygen minimum zone in the North Pacific and enhanced CO2 sequestration at mid-depth waters. We attribute the millennial-scale changes to intensified NPIW and enhanced abyss flushing during deglacial cold and warm intervals, respectively, closely related to variations in North Atlantic Deep Water formation. Out study extends the millennial-scale links between ventilation in the subtropical North Pacific Ocean and the Atlantic Climate into the last glaciations, highlighting the key roles of Atlantic Meridional Overturning Circulation in regulating the North Pacific environment at millennial timescales. Note: Financial support was provided by the National Program on Global Change and Air-Sea Interaction (GASI-GEOGE-04) and by the National Natural Science Foundation of China (Grant Nos.: 41876065, 41476056, and U1606401).

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Sensitivity of the Simulated Distributions of Water Masses, CFCs, and Bomb 14C to Parameterizations of Mesoscale Tracer Transports in a Model of the North Pacific

Journal of Physical Oceanography ◽

10.1175/jpo2854.1 ◽

2006 ◽

Vol 36 (3) ◽

pp. 273-285 ◽

Cited By ~ 4

Author(s):

Yongfu Xu ◽

Shigeaki Aoki ◽

Koh Harada

Keyword(s):

North Pacific ◽

General Circulation ◽

Western North Pacific ◽

North Pacific Ocean ◽

Circulation Model ◽

Water Masses ◽

Intermediate Water ◽

North Pacific Intermediate Water ◽

The North ◽

The North Pacific

Abstract A basinwide ocean general circulation model of the North Pacific Ocean is used to study the sensitivity of the simulated distributions of water masses, chlorofluorocarbons (CFCs), and bomb carbon-14 isotope (14C) to parameterizations of mesoscale tracer transports. Five simulations are conducted, including a run with the traditional horizontal mixing scheme and four runs with the isopycnal transport parameterization of Gent and McWilliams (GM). The four GM runs use different values of isopycnal and skew diffusivities. Simulated results show that the GM mixing scheme can help to form North Pacific Intermediate Water (NPIW). Greater isopycnal diffusivity enhances formation of NPIW. Although greater skew diffusivity can also generate NPIW, it makes the subsurface too fresh. Results from simulations of CFC uptake show that greater isopycnal diffusivity generates the best results relative to observations in the western North Pacific. The model generally underestimates the inventories of CFCs in the western North Pacific. The results from simulations of bomb 14C reproduce some observed features. Greater isopycnal diffusivity generates a longitudinal gradient of the inventory of bomb 14C from west to east, whereas greater skew diffusivity makes it reversed. It is considered that the ratio of isopycnal diffusivity to skew diffusivity is important. An increase in isopycnal diffusivity increases storage of passive tracers in the subtropical gyre.

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