Polar ice melt

An urgent priority for scientists is estimating the rate at which the Antarctic ice sheet will melt over the coming decades and centuries.

Despite our ever-improving understanding of ice sheet dynamics, difficulties associated with modelling polar ice sheet response to climate change remains the largest source of uncertainty in global sea-level projections. This is especially true when modelling the Antarctic Ice Sheet. 

One of the primary objectives of Te Ao Hurihuri Te Ao Hou is to generate new constraints on ice sheet behaviour from historical records. These constraints are used to test and improve ice flow models that are commonly used to predict how the Greenland and Antarctic ice sheets change as air and ocean temperatures increase.

In West Antarctica, warm ocean currents erode and thin the bottom of large floating ice shelves, causing accelerating loss of the highly vulnerable West Antarctic Ice Sheet which largely sits below sea level; while the vast East Antarctic ice sheet may gain mass, as warmer temperatures cause increased snowfall. This results in a greater range of future possibilities, from ice sheet growth that decreases sea level by 7.8 cm to ice sheet melt that increases sea level by 30 cm by 2100.

The main cause of the differences between the Antarctic Ice Sheet model projections is the extent to which they incorporate processes that control the rapid melting of ice shelves as well as rapid irreversible retreat into deep basins below sea level. 

Many of the models underestimate modern melt rates at the base of ice shelves. Better understanding of ocean circulation underneath the ice shelves is therefore critical for improving these ice flow models. This is why the IPCC has a “low confidence” and “medium confidence” set of projections for the global sea-level rise.