Research

Calving dynamics and ice shelf damage

About 30% of the ice discharge in Greenland and 50% in Antarctica is from iceberg calving. Since the 1990s, we have observed in Greenland that warmer ocean waters trigger ice-front retreats of marine-terminating glaciers, and the corresponding loss in resistive stress leads to glacier acceleration and thinning. We have implemented a level-set based method to track moving boundaries within our ice sheet model. In Antarctica, Larsen A and Larsen B have collapsed, and we are working on better understanding the evolution of damage of large ice shelves. Read more…

Bed topography mapping

We have devised a new method to infer the bed topography beneath the ice sheets at high resolution (150 m) based on the conservation of mass and optimization. Recently, we mapped the entire coast of Greenland (Morlighem et al. 2014) and showed that glaciers flow down well-defined, deep topographic channels with deep narrow depressions within mountain block landscapes, suggesting that the ice sheet will be vulnerable to more rapid retreat in the coming century than previously thought. Read more…

Ice-Ocean interactions

Over the past decades, many glaciers along the coast of Greenland have been retreating and accelerating, sometimes dramatically. The retreat of these glaciers is initiated by the presence of warm and salty subsurface Atlantic Water (AW) in the fjords. Similarly in Antarctica, some sectors such as the Amundsen sea embayment are experiencing dramatic grounding line retreat and ice flow acceleration. These changes have been linked to the inflow of warm Circumpolar Deep Water (CPDW) onto the continental shelf. Improving our understanding of the physics of  ice-ocean interactions and how to include them in numerical models is therefore critical in order to improve our ability to project the dynamics of the ice sheets. Read more…

Ice-Atmosphere interactions

Glacier ice forms by the slow transformation of snow into ice. Changes in precipitation patterns or in surface temperatures directly affect the mass balance of the ice sheets. Surface meltwater also can make its way to the bed, potentially changing basal conditions on different temporal time scale, and also affect the rate of undercutting at glacier termini. Ice-atmosphere interactions are an important focus of our research group. Read more…

Subglacial Hydrology

The presence of water at the ice-bed interface changes the basal boundary conditions of the ice sheet and may be responsible to changes in ice flow speed through changes in effective pressure. The routing of meltwater to the ocean also controls the strength of the circulation of the ocean in Greenland fjord, which directly affects the rate at which outlet glaciers produce icebergs. We are currently working on two different approaches to model hydrology: a dual continuum model, and a novel unified formulation (SHAKTI). Read more…

Paleoclimate modeling

Over the past few years, our group has been using new generation modeling technique to focus on the Holocene, where important paleoclimate archives constraining the past margin migration history of the ice sheet exist.  We investigate how changes in climatic conditions affected the rate of retreat of the Greenland ice sheet. Read more…

Numerics

Our group has co-founded the Ice Sheet System Model in partnership between UC Irvine and the NASA Jet Propulsion Laboratory. ISSM is a large scale, high-resolution, massively parallelized finite element model dedicated to ice sheet modeling and is our primary tool to address the science questions we are interested in. We develop new finite-elements for specific applications, automatic differentiation tools, and test test implementations of physical processes.  Read more…

Thwaites Glacier Collaboration

Thwaites Glacier, in West Antarctica, has been accelerating and widening over the past three decades. How fast Thwaites will disintegrate or how quickly it will find a new stable state have become some of the most important questions of the future of the West Antarctic Ice Sheet and its contribution to sea level rise over the next century and beyond.  Our group is leading the project “PROcesses, drivers, Prediction: modeling the History and Evolution of Thwaites” (PROPHET)! Read more…