Frontal circulation and submesoscale variability during the formation of a Southern Ocean mesoscale eddy

AbstractObservations made in the Scotia Sea during the May 2015 Surface Mixed Layer Evolution at Submesoscales (SMILES) research cruise captured submesoscale, O(1-10 km), variability along the periphery of a mesoscale O(10-100 km) meander precisely as it separated from the Antarctic Circumpolar Current (ACC) and formed a cyclonic eddy ~ 120 km in diameter. The meander developed in the Scotia Sea, an eddy-rich region east of the Drake Passage where the Subantarctic and Polar fronts converge and modifications of Subantarctic mode water (SAMW) occur. In situ measurements reveal a rich submesoscale structure of temperature and salinity and a loss of frontal integrity along the newly-formed southern sector of the eddy. A mathematical framework is developed to estimate vertical velocity from co-located drifter and horizontal water velocity time series, under certain simplifying assumptions appropriate for the current data set. Upwelling (downwelling) rates of O(100 m day-1) are found in the northern (southern) eddy sector. Favorable conditions for submesoscale instabilities are found in the mixed layer, particularly at the beginning of the survey in the vicinity of density fronts. Shallower mixed layer depths and increased stratification are observed later in the survey on the inner edge of the front. Evolution in T-S space indicates modification of water mass properties in the upper 200 m over 2 days. Modifications along �θ 27 - 27.2 kg m�3 have climate-related implications for mode and intermediate water transformation in the Scotia Sea on finer spatiotemporal scales than observed previously

From sea ice to seals: a moored marine ecosystem observatory in the Arctic

Although Arctic marine ecosystems are changing rapidly, year-round monitoring is currently very limited and presents multiple challenges unique to this region. The Chukchi Ecosystem Observatory (CEO) described here uses new sensor technologies to meet needs for continuous, high-resolution, and year-round observations across all levels of the ecosystem in the biologically productive and seasonally ice-covered Chukchi Sea off the northwest coast of Alaska. This mooring array records a broad suite of variables that facilitate observations, yielding better understanding of physical, chemical, and biological couplings, phenologies, and the overall state of this Arctic shelf marine ecosystem. While cold temperatures and 8 months of sea ice cover present challenging conditions for the operation of the CEO, this extreme environment also serves as a rigorous test bed for innovative ecosystem monitoring strategies. Here, we present data from the 2015–2016 CEO deployments that provide new perspectives on the seasonal evolution of sea ice, water column structure, and physical properties, annual cycles in nitrate, dissolved oxygen, phytoplankton blooms, and export, zooplankton abundance and vertical migration, the occurrence of Arctic cod, and vocalizations of marine mammals such as bearded seals. These integrated ecosystem observations are being combined with ship-based observations and modeling to produce a time series that documents biological community responses to changing seasonal sea ice and water temperatures while establishing a scientific basis for ecosystem management.</p

An easy-to-use scoring index to determine severity of mitral regurgitation by 2D echocardiography in clinical practice

Thoracic Surger