Next generation projections of sea level contribution and freshwater export from the Greenland Ice Sheet

Loss of ice from glaciers and ice sheets is one of the most obvious consequences of global warming. As the planet warms we can expect increased rates of ice loss, and this ice ultimately ends up in the ocean causing sea level rise. Accurate projections of sea level rise are hugely valuable for societies around the world to make the best decisions on how to adapt to the increased risk of flooding in coastal areas. Ice loss also releases vast quantities of freshwater into the ocean, which has the potential to affect ocean currents, particularly in the North Atlantic where these currents are critical in regulating our climate. Accurate projections of freshwater flux into the North Atlantic from ice loss are therefore hugely important to assess whether the loss of ice will be sufficient to affect large-scale ocean currents, with implications for global climate. The Greenland Ice Sheet is a vast mass of ice located in the North Atlantic, and is a key current and future source of global sea level rise and freshwater flux into the North Atlantic. Ice in Greenland is lost in two ways: (i) through melting of the ice sheet surface, forming liquid freshwater which flows into the ocean, and (ii) due to the flow of ice into the ocean through vast rivers of ice called tidewater glaciers; these glaciers produce huge icebergs which melt in the ocean. While reasonable confidence exists in our projections of ice sheet surface melting, projections of the flow of ice into the ocean are significantly less advanced. Projections of the flow of ice into the ocean in Greenland have to date been held back by (i) a lack of understanding of how the flow responds to climate change (though it is thought that recent increases in ice flow are related to warmer ocean temperatures), and (ii) the high computational costs of running models of future ice flow into the ocean. The research proposed in this fellowship will offer novel solutions to these problems, increasing confidence in projections of sea level rise and freshwater flux from the Greenland Ice Sheet. Specifically, I will develop a simple model for the transport of warm water from the ocean to the edge of the ice sheet, allowing us to quickly quantify the temperature of the ocean water which affects the ice sheet. I will also use datasets of ocean and air temperature and glacier behaviour from the past 100 years to develop simple relationships between glacier retreat and regional climate change. These two key developments will allow me to run computer simulations of the Greenland Ice Sheet which capture the flow of ice into the ocean, and its future evolution in a warming climate. With these computer simulations I will produce projections, with associated uncertainties, of future sea level rise and freshwater export into the North Atlantic from the Greenland Ice Sheet over the coming two centuries.