Numerical modeling of ocean‐ice interactions under Pine Island Bay's ice shelf

Abstract

[1] A two-dimensional numerical model is used to simulate the dynamics of buoyant, meltwater-rich plumes flowing beneath the ice shelf occupying much of Pine Island Bay, West Antarctica. Recent studies have shown that this ice shelf, along with all others fringing the Amundsen Sea, is thinning rapidly. In the model, both the Coriolis effect and subshelf topography are important in controlling plume dynamics and the spatial distribution of ice melt. Melt is concentrated in a narrow zone within $20 km of the grounding line where steep subshelf slopes and access to warm ambient water allow melt rates to exceed 100 m yr À1 . The plume generated by entrainment of ambient water into the meltwater in these areas is guided by the topography of the ice shelf underside and exits the ice shelf at three distinct outflow locations. Melt rates generated along the course of the plume are higher (approximately 2.5Â) than rates elsewhere. The model suggests that the observed ice shelf thinning rates could have resulted from a hypothetical instantaneous 0.25°C warming of the ambient water entrained by the plume. A context for this value is provided by the 40-year warming trend documented by Jacobs et al.

A box model of circulation and melting in ice shelf caverns

“…A 'warm tub' environment is supposed to exist underneath Pine Island Glacier (PIG) where different techniques infer melting near the grounding line in excess of 40 m/y (Rignot andJacobs, 2002, Payne et al 2007). The relatively simple geometry of the PIG cavern invites the application of numerical models of different complexity , Payne et al 2007, Thoma et al 2008 which confirm the high melt rates in the deep interior and provide a mean basal melting of up to 20 m/y. However, it is still a matter of debate, with consequences for climate warming and related SLR, whether the dependency of the basal mass loss on the external ocean temperature is simply linear or of higher order .…”

“…Except for this extremely coarse resolution, the box model's physics are those implemented in high resolution circulation models of cavern systems (e.g. Payne et al 2007, Dinniman et al 2007.…”

Channelization of plumes beneath ice shelves

“…These in turn are approximations of parameterizations with more complicated dependence on the Richardson number (for entrainment) and Reynolds number (for heat transfer) (Payne et al 2007;Holland et al 2007), which were used in the numerical studies of Sergienko (2013) and Gladish et al (2012). With such additional complexities, the base state would again have to be computed numerically.…”

“…The formulation of turbulent stresses follows that of Gladish et al (2012), Holland et al (2007) and Payne et al (2007). One could potentially argue for alternative formulations of these terms, either with D moved inside the final derivative or with mixed-derivative terms that echo the viscous stretching terms in (2.1c)-(2.1d).…”

Response of sub-ice platelet layer thickening rate to variations in Ice Shelf Water supercooling in McMurdo Sound, Antarctica

“…< 0) to variations in ocean temperature has been investigated with 10 observations (Rignot and Jacobs, 2002;Shepherd et al, 2004) and model results (Grosfeld and Sandhäger, 2004;Holland et al, 2008;Payne et al, 2007;Walker and Holland, 2007;Williams et al, 1998Williams et al, , 2002. In contrast, we know of no studies to date of the response of marine ice (or SIPL) thickening rate beneath ice shelves (or sea ice) to variations in supercooling (i.e.…”