Abstract
The spectrum of linear free modes of a reduced-gravity ocean in a closed basin with weak dissipation is examined. The constraint of total mass conservation, which in the quasigeostrophic formulation determines the pressure on the boundary as a function of time, allows the existence of selected large-scale, low-frequency basin modes that are very weakly damped in the presence of dissipation. These weakly damped modes can be quasi-resonantly excited by time-dependent forcing near the eigenperiods, or during the process of adjustment to Sverdrup balance with a steady wind from arbitrary initial conditions. In both cases the frequency of the oscillations is a multiple of 2 p /t 0, where t 0 is the long Rossby wave transit time, which is of the order of decades for midlatitude, large-scale basins. These oscillatory modes are missed when the global mass conservation constraint is overlooked.
Highlights
Pine Island, Thwaites, Haynes, Smith, Pope, and Kohler Glaciers are among the fastest-flowing glaciers in continental Antarctica [Rignot et al, 2011b]
Pine Island Glacier is 30 km wide at the grounding line, fed by nine tributaries, and developing a 55 km long floating section that flowed at 4 km/yr in 2006
Thwaites Glacier is 120 km wide, with a 60 km wide fast-moving section that develops into the Thwaites Glacier Tongue to the west and a 60 km wide slower-moving section that flows into an ice shelf buttressed by ice rumples to the east, the Thwaites Eastern Ice Shelf (TEIS), an unofficial name
Summary
Pine Island, Thwaites, Haynes, Smith, Pope, and Kohler Glaciers are among the fastest-flowing glaciers in continental Antarctica [Rignot et al, 2011b]. Combined together, they drain one third of the West Antarctic Ice Sheet into the Amundsen Sea Embayment (ASE), or 393 million square kilometers. The ASE glaciers are major contributors to sea level rise from Antarctica with about 0.28 ± 0.05 mm/yr between 2005 and 2010 [Shepherd et al, 2012], which itself amounts to about 10% of the global sea level rise (3 mm/yr) [Church and White, 2011]. These glaciers and their catchment basins combined contain 1.2 m global sea level rise
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