Modeling ice-ocean dynamics in ice-shelf rifts.

Abstract:

Ice-shelf break-up is thought to be driven by a combination of various environmental factors that can be classified as oceanographic, glaciological and atmospheric. These contribute to different phases of the ice damaging process. However, physical processes driving ice-shelf collapse and rift propagation are still poorly understood. A few studies have suggested that ice-shelf rifting can be highly influenced by the rift's infill. In particular, mélange, a heterogeneous mixture of sea ice, marine ice, and trapped icebergs, is thought to stabilize rift evolution, potentially slowing or halting rift growth.

In this study, we investigate ocean dynamics associated with rifts in ice-shelves using the Massachusetts Institute of Technology ocean general circulation model. Our goal is to estimate the effects of rifts on ice-shelf melting and freezing processes and in turn on sub-ice shelf circulation. Enhanced (reduced) melting/freezing rates induced by ice-shelf rifts affect the physical properties of the volume confined between rift's flanks. Here, we examine key hydrographic conditions on sensitivities to the cracked ice-shelf basal environment in an idealized set-up. We find that basal fractures modify the thermohaline circulation by accumulation of cold and fresh water in the rift’s open volume, which potentially is a prerequisite for mélange formation. An improved representation of ice-ocean interactions below a fractured ice-shelf is a step toward a better understanding of rifting processes and, on a larger scale, of ice-shelves collapse. To further study this, we use a more realistic regional set-up of Larsen C in the Antarctic Peninsula.