Observation and understanding changes in the mass of the Greenland ice sheet using data from GRACE and remote sensing satellites

PhD student: Jiangjun Ran

The on-going global warming may have a number of serious consequences in the coming decades. One of them is global sea level rise, which may have a catastrophic impact for hundreds of millions of people living in coastal areas world-wide. Due to the enormous scale of this problem, it can only be managed on the basis of a careful long-term planning. Such a planning requires, in particular, an accurate estimation of future rates of water level rise. This is not an easy task. In particular, it is difficult to predict the contribution of the dynamic discharge of the polar ice sheets, where a large amount of water is stored. For instance, melting of the entire Greenland ice sheet would rise the sea level, in average, by about 7 meters.

In order to understand and predict the future behavior of ice sheets, it is necessary, in particular, to analyze available data. One of most important sources of such data is satellite gravimetry mission Gravity Recovery and Climate Experiment (GRACE). This mission is capable of measuring tiny variations of the gravity field caused by mass re-distribution. As such, this mission can be used to obtain direct estimates of changes in ice sheet mass. Another way to monitor ice sheets is to measure elevation changes using satellite altimetry missions, like ICESat and Cryosat. Altimetry data contain information only about volume changes, so that additional information about the density of the material responsible for the changes is needed. This limitation is compensated by a much higher spatial resolution that achievable with satellite gravimetry.

In the course of the project, possible ways to achieve the highest possible spatial resolution of GRACE-based mass change estimates will be investigated. Moreover, it will be studied how this resolution can be further improved by combining GRACE and remote sensing data. After that, we intend to isolate the dynamic discharge component from the observed changes, for which purpose appropriate models of precipitation and water melting are to be used. Finally, quantitative
links between the recovered dynamic discharge and environmental conditions (particularly, air temperature) are to be established. In combination with ice dynamics modeling, this information will lead to better quantification and understanding of ice dynamics.