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Seaglider surveys at Ocean Station Papa: Circulation and water mass properties in a meander of the North Pacific Current
Author(s) -
Pelland Noel A.,
Eriksen Charles C.,
Cronin Meghan F.
Publication year - 2016
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2016jc011920
Subject(s) - meander (mathematics) , acoustic doppler current profiler , water mass , mesoscale meteorology , geology , pycnocline , current (fluid) , ocean current , climatology , anticyclone , oceanography , mooring , current meter , boundary current , geometry , mathematics
A Seaglider autonomous underwater vehicle augmented the Ocean Station Papa (OSP; 50°N, 145°W) surface mooring, measuring spatial structure on scales relevant to the monthly evolution of the moored time series. During each of three missions from June 2008 to January 2010, a Seaglider made biweekly 50 km × 50 km surveys in a bowtie‐shaped survey track. Horizontal temperature and salinity gradients measured by these surveys were an order of magnitude stronger than climatological values and sometimes of opposite sign. Geostrophically inferred circulation was corroborated by moored acoustic Doppler current profiler measurements and AVISO satellite altimetry estimates of surface currents, confirming that glider surveys accurately resolved monthly scale mesoscale spatial structure. In contrast to climatological North Pacific Current circulation, upper‐ocean flow was modestly northward during the first half of the 18 month survey period, and weakly westward during its latter half, with Rossby number O ( 0.01 ) . This change in circulation coincided with a shift from cool and fresh to warm, saline, oxygen‐rich water in the upper‐ocean halocline, and an increase in vertical fine structure there and in the lower pycnocline. The anomalous flow and abrupt water mass transition were due to the slow growth of an anticyclonic meander within the North Pacific Current with radius comparable to the scale of the survey pattern, originating to the southeast of OSP.