|Title||The North Pacific Oxygen uptake rates over the past half century|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Authors||Kwon E.Y, Deutsch C., Xie SP, Schmidtko S., Cho Y.K|
|Journal||Journal of Climate|
|Type of Article||Article|
|Keywords||Atm; Central Mode Water; circulation; climate; climate-change; data assimilation analysis; decadal variability; dynamics; intermediate; mixed-layer; ocean; Ocean circulation; Ocean dynamics; Pacific decadal oscillation; Phenomena; sea; seasonal cycle; structure; sub-arctic pacific; subduction; Thermocline circulation; upper ocean 1950-95; variability; water|
The transport of dissolved oxygen (O-2) from the surface ocean into the interior is a critical process sustaining aerobic life in mesopelagic ecosystems, but its rates and sensitivity to climate variations are poorly understood. Using a circulation model constrained to historical variability by assimilation of observations, the study shows that the North Pacific thermocline effectively takes up O-2 primarily by expanding the area through which O-2-rich mixed layer water is detrained into the thermocline. The outcrop area during the critical winter season varies in concert with the Pacific decadal oscillation (PDO). When the central North Pacific Ocean is in a cold phase, the winter outcrop window for the central mode water class (CMW; a neutral density range of = 25.6-26.6) expands southward, allowing more O-2-rich surface water to enter the ocean's interior. An increase in volume flux of water to the CMW density class is partly compensated by a reduced supply to the shallower densities of subtropical mode water ( = 24.0-25.5). The thermocline has become better oxygenated since the 1980s partly because of strong O-2 uptake. Positive O-2 anomalies appear first near the outcrop and subsequently downstream in the subtropical gyre. In contrast to the O-2 variations within the ventilated thermocline, observed O-2 in intermediate water (density range of = 26.7-27.2) shows a declining trend over the past half century, a trend not explained by the open ocean water mass formation rate.