Monitoring the temporal changes in the gravity field, oceans, land water and ice masses in North America by means of integrated satellite data

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Scientific research has shown, and the fifth assessment report on the Earth's climate of the UN’s Intergovernmental Panel on Climate Change (IPCC) has asserted, that we are seeing changes in the climate system unprecedented in records spanning hundreds of years. The glaciers and ice caps are diminishing, sea level is rising and the water cycle is changing, just to name a few. More extreme weather events, severe coastal inundation and even depletion of water resources are forecasted, as is the persistence of these climate changes for centuries. Data from Earth-observing satellites are an invaluable tool for monitoring, modeling and predicting such changes, and the natural hazards they will cause, on a global scale. The proposed research program will contribute to this long-term goal by quantifying and modeling some of these effects, with focus in Canada and North America. It will allow proper assessment of the aforementioned effects of climate change, and thus will enable informed government decisions for their mitigation. In particular, this research will focus on the determination of temporal changes in the geoid (the equipotential surface of the Earth’s gravity field coinciding with the idealized oceans at rest), sea level, land water and ice masses. This has become possible primarily through the use of data from the GRACE satellite mission, which senses the integrated gravity change induced by the redistribution of masses related to geophysical processes in the fluid and solid Earth. These include hydrological, atmospheric and oceanic mass variability, viscoelastic Earth deformation due to glacial isostatic adjustment (GIA), and elastic deformation due primarily to climate-related ice mass changes. The identification, separation and interpretation of all these signals is a very daunting task and will be a key aspect of this research program. The first major objective is to determine the total temporal mass redistribution in the Earth System and in particular its effect on the geoid in North America. Since the geoid surface is used as the reference surface for land and ocean heights/depths (vertical datum), its monitoring is essential for understanding changes in the level of the oceans, ice and land water, and is therefore intimately related to the study of the other three objectives of this research. In addition, this will support and inform the Canadian and US governments’ recent decision to modernize their height systems by use of a geoid-based vertical datum. The second major objective is to study how the mean sea surface (MSS) of the oceans changes over time, an important factor for understanding coastal hazards such as flooding and storm surges. Data from radar and laser satellite altimetry missions will be merged to compute the changing MSS, and to better understand ocean circulation. The third major objective is the use of GRACE data together with hydrology models for regional and global hydrology studies and for GIA determination in North America. The knowledge gained from the Soil Moisture and Ocean Salinity (SMOS) and GRACE satellite data and hydrology models will strengthen forecasting and possibly predicting hazardous events such as floods (and even droughts and heat waves) and changes in precious natural resources such as land water over North America. The fourth major objective is to use satellite data from GRACE as well as from ice altimetry missions, such as NASA’s ICESat and ESA’s CryoSat missions, to determine the ice mass loss in the northern hemisphere and its contribution to sea level rise. Retreating sea ice will also be studied because, if sustained, it will have a tremendous economic impact since it will make navigation and resource exploration possible in the Arctic regions of Canada.