Modelling the Surface Mass Balance of the Greenland Ice Sheet and Neighbouring Ice Caps, Brice Nöel

Brice Nöel, University of Utrecht

The Greenland ice sheet (GrIS) is the world’s second largest ice mass, storing about one tenth of the Earth’s freshwater. Totally melted, global sea level would rise by 7.4 m, affecting low-lying regions worldwide. Since the mid-1990s, increased atmospheric and oceanic temperatures have accelerated GrIS mass loss through increased meltwater runoff and icebergs discharge from marine-terminating glaciers. To study the recent GrIS mass loss, we use a climate model that simulates the GrIS surface mass balance (SMB), i.e. the difference between winter snowfall and summer runoff.

Using the model, we identify 1997 as a tipping point for the mass balance of Greenland’s peripheral ice caps (GICs), i.e. detached from the main ice sheet. These ice caps are covered by porous snow that acts as a ”sponge” absorbing a large amount of meltwater, which subsequently refreezes in winter. The excess meltwater runs off to the ocean, contributing to mass loss. Until 1997, the snow could actively sponge and refreeze meltwater. Around 1997, decades of increased melt saturated the snow, so that additional melt is now forced to run off to the ocean, tripling the mass loss. Likewise, ice caps of the Canadian Arctic underwent uninterrupted mass loss during the last six decades. Consequently, these ice caps will likely undergo irreversible mass loss in the future. The Greenland ice sheet is still safe, as porous snow absorbs most of the summer melt. However, the tipping point crossed by Arctic ice caps must be regarded as an alarm-signal for the ice sheet.

Brice Noël specializes in glacier and climate modeling at the Institute for Marine and Atmospheric Research, at Utrecht University. His research analyzes the dynamics of glacier mass loss at the Jacobshavn Glacier through the use of airborne altimetry and satellite imaging. His book, Modeling the Surface Mass Balance of the Greenland Ice Sheet and Neighbouring Ice Caps: A Dynamical and Statistical Downscaling Approach, discusses the development of a statistical downscaling algorithm that projects an existing meteorological model onto a 1km grid (as opposed to the standard 11km grid). Based on the output from this new model, Noël’s research team identifies 1997 as the tipping point for the mass balance of the Greenland Ice Caps. Since that time, the Ice Caps have become saturated with meltwater and have sustained mass loss. Noël and his research team have published in the journals CryosphereNature, and Journal of Geophysical Research.