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Browsing by Subject "oceanography"

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  • Sholeninova, Polina (2021)
    The Arctic Ocean is known to be inhabited with energetic mesoscale eddies commonly detected in depths from 200 m to 1200 m. Due to their high energetics and ability to transfer momentum, heat, salt and biochemical properties for long distances from their origin, eddies may considerably affect the structure of a water column in the Arctic Ocean. This study investigated an anticyclonic eddy event detected at one of the mooring stations deployed under the Nansen and Amundsen Basins Observational System project. The mooring located at the deep part of the continental slope of the Laptev Sea and conducted autonomous measurements during the years 2013–2015. The conductivity-temperature-depth, as well as current measurements from the Acoustic Doppler Current Profiler in the upper ocean (24–82 m) and from the McLane Moored Profiler in the intermediate layer (88–760 m), were examined. Spectral analysis of the currents and calculation of the eddy available potential energy were performed. This study revealed a mesoscale eddy with the core centred deeper than 750 m drifted past the mooring for 2 months. Its horizontal length scale was ∼128 km. The water properties typical for the Fram Strait Branch of the Atlantic water carried by the subsurface boundary current were trapped in the eddy. This study suggests that the eddy was originated from the baroclinic instability of the front between the Fram Strait Branch and the Barents Sea Branch of the Atlantic water flow.
  • Murakami, Margaret (2023)
    Antarctic Bottom Water (AABW), a water mass that sinks to form the deepest limb of the meridional overturning circulation (MOC), is a key control on the ventilation of the Southern Ocean as well as global exchanges of heat, freshwater, and carbon. Sources of this water mass include latent heat polynyas found in Prydz Bay, East Antarctica, which expose the Southern Ocean to the colder atmosphere and are important sources of high salinity shelf water (HSSW). This water mass is the precursor to Dense Shelf Water (DSW) which can be exported from the continental shelf to form Antarctic Bottom Water (AABW). In this study, Lagrangian particle tracking of water masses within Prydz Bay was used to investigate the roles of seasonality, bathymetry, and the presence of other water masses on the mechanisms of water mass transformation (WMT), a series of key processes in the MOC. Online particles were released weekly within the Prydz Bay polynya region in a 10 km resolution simulation of the Whole Antarctic Ocean Model (WAOM10) and their forward trajectories were tracked for one year. Results highlight the export of Prydz Bay water along the westward Antarctic Slope Current (ASC). Cluster analysis of the results shows a winter signal for bottom water forming particles. When advected beneath the ice shelf, polynya water can mix with fresh meltwater, becoming less dense and forming ice shelf water (ISW). After this polynya-originating water departs the ice shelf again, its increased buoyancy can make future AABW formation less likely. This study confirms that the presence of modified circumpolar deep water (mCDW) can play a controlling factor in rates of DSW export as bottom water. Results show export of DSW from the Prydz Channel and Cape Darnley, mixing either along or across isopycnals depending on the influence of other water masses and cross-slope flow. Interactions with the ASC and major topographic features including the Enderby Land projection and several underwater canyons appear to influence the export of water to the deep ocean. WAOM10 finds realistic ratios of AABW formation as compared with observational data and shows greater low-density water formation than other models.