[PDF] A Numerical Study Of Ocean Circulation And Ice Ocean Interaction Beneath The Amery Ice Shelf Antarctica eBook

Author : David M. Holland
Publisher : Elsevier Inc. Chapters
Page : 79 pages
File Size : 17,69 MB
Release : 2013-10-22
Category : Science
ISBN : 012805865X

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The polar oceans interact with both sea ice, formed in situ at the ocean surface, and land ice, flowing under gravity from the land onto the ocean surface. This ice–ocean interaction has profound consequences for the ocean and climate in a number of ways: a change in ocean surface albedo and surface energy balance where there is ice cover compared with open ocean, a change in global sea level when land ice flows into the ocean, and a transformation of water masses through melting or freezing of ice which subsequently influences the global conveyor belt. Another type of ice–ocean interaction, less well understood, is that between marine permafrost at the seafloor and the overlying ocean waters. Collectively, we refer to sea ice, land ice, and marine permafrost as the marine cryosphere. In this chapter, we review current understanding of the interaction of the marine cryosphere with the global ocean and discuss emerging technologies to improve observations and numerical modeling of these interactions. Projections for the state of the marine cryosphere into the current century and beyond are reviewed.

Author : Stanley S. Jacobs
Publisher : American Geophysical Union
Page : 400 pages
File Size : 22,90 MB
Release : 1998-02-04
Category : Science
ISBN :

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In this latest oceanology volume of the Antarctic Research Series, polar scientists describe and model air-sea and ice-ocean interactions, the formation and chemistry of deep and bottom waters, regional circulations, tidal heights and currents, ocean bathymetry, interannual variability and the Antarctic Slope Front.

Author : Carl Wunsch
Publisher : Elsevier Inc. Chapters
Page : 68 pages
File Size : 37,14 MB
Release : 2013-10-22
Category : Science
ISBN : 0128058706

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The World Ocean Circulation Experiment drove the development of estimates of the decadal scale time evolving general circulation that are dynamically and kinematically consistent. A long timescale, and a goal of estimation rather than prediction, preclude the use of meteorological methods called “data assimilation (DA).” Instead, “state estimation” methods are reviewed here and distinguished from DA. Results from the dynamically consistent family of solutions from the project Estimating the Circulation and Climate of the Ocean based upon least-squares Lagrange multipliers (adjoints) are used to discuss the determination of the dominant elements of the circulation in the period since 1992—which marked the beginning of the satellite altimetric record. Significant changes documented in the Arctic in recent decades now mandate consideration of the coupled ocean-cryospheric state.

Author : Beau Riffenburgh
Publisher : Taylor & Francis
Page : 1274 pages
File Size : 42,76 MB
Release : 2007
Category : History
ISBN : 0415970245

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Author : Véronique Dansereau
Publisher :
Page : 123 pages
File Size : 22,71 MB
Release : 2012
Category : Ocean circulation
ISBN :

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Interactions between the ocean circulation in sub-ice shelf cavities and the overlying ice shelf have received considerable attention in the context of observed changes in flow speeds of marine ice sheets around Antarctica. Modeling these interactions requires parameterizing the turbulent boundary layer processes to infer melt rates from the oceanic state at the ice-ocean interface. Here we explore two such parameterizations in the context of the MIT ocean general circulation model coupled to the z-coordinates ice shelf cavity model of Losch (2008). We investigate both idealized ice shelf cavity geometries as well as a realistic cavity under Pine Island Ice Shelf (PIIS), West Antarctica. Our starting point is a three-equation melt rate parameterization implemented by Losch (2008), which is based on the work of Hellmer and Olbers (1989). In this form, the transfer coefficients for calculating heat and freshwater fluxes are independent of frictional turbulence induced by the proximity of the moving ocean to the fixed ice interface. More recently, Holland and Jenkins (1999) have proposed a parameterization in which the transfer coefficients do depend on the ocean-induced turbulence and are directly coupled to the speed of currents in the ocean mixed layer underneath the ice shelf through a quadratic drag formulation and a bulk drag coefficient. The melt rate parameterization in the MITgcm is augmented to account for this velocity dependence. First, the effect of the augmented formulation is investigated in terms of its impact on melt rates as well as on its feedback on the wider sub-ice shelf circulation. We find that, over a wide range of drag coefficients, velocity-dependent melt rates are more strongly constrained by the distribution of mixed layer currents than by the temperature gradient between the shelf base and underlying ocean, as opposed to velocity-independent melt rates. This leads to large differences in melt rate patterns under PIIS when including versus not including the velocity dependence. In a second time, the modulating effects of tidal currents on melting at the base of PIIS are examined. We find that the temporal variability of velocity-dependent melt rates under tidal forcing is greater than that of velocity-independent melt rates. Our experiments suggest that because tidal currents under PIIS are weak and buoyancy fluxes are strong, tidal mixing is negligible and tidal rectification is restricted to very steep bathymetric features, such as the ice shelf front. Nonetheless, strong tidally-rectified currents at the ice shelf front significantly increase ablation rates there when the formulation of the transfer coefficients includes the velocity dependence. The enhanced melting then feedbacks positively on the rectified currents, which are susceptible to insulate the cavity interior from changes in open ocean conditions.