Greenland Ice Sheet's Albedo Loss Accelerates Global Sea Level Rise

The Greenland Ice Sheet: An Alarming Shift in Global Dynamics

The Greenland Ice Sheet (GrIS), the planet's second-largest mass of permanent ice, covers approximately 1.7 million square kilometers and contains enough frozen water to raise global sea levels by an astounding 6 meters if fully melted.

Illustration 1: Greenland Ice Sheet At Scale

Transition to Instability

A fundamental shift has occurred in the GrIS's status over the past two decades. Previously viewed as a stable, slow-moving system, it is now the largest single contributor to global sea level rise, adding up to 1.2 millimeters per year. This acceleration in mass loss is a clear response to global warming.

The vulnerability of the GrIS was dramatically illustrated during the summer of 2019. An intense heatwave that swept through Europe eventually reached Greenland, leading to record-high air temperatures. During a critical period spanning the end of July and beginning of August, an unprecedented 90% of the entire ice sheet surface experienced melting. This single event generated roughly 55 billion tons of meltwater.

Illustration 2: Greenland Ice Sheet From Space

The Supraglacial Lakes and the Albedo Feedback

This vast amount of meltwater is not merely draining away; it is fundamentally altering the ice sheet's surface characteristics through the formation of supraglacial lakes. These lakes, ranging in size from a few square meters up to several square kilometers, form in localized depressions, are numerous and expansive, and are easily monitored by satellite.

The crucial impact of these lakes is their effect on surface albedo (reflectivity):

• Albedo Mechanics: Albedo is a measure of the fraction of solar radiation reflected back into space. Clean snow and ice have a high albedo, meaning they reflect most incoming solar energy, thus limiting warming. Water, in stark contrast, has a low albedo and absorbs significantly more energy.

  
  

• The Positive Feedback Loop: As global temperatures rise, more melting occurs, increasing the size, number, and total area of these supraglacial lakes. This effectively lowers the overall albedo of an expanding region of the GrIS surface. The darker surface absorbs more solar radiation, which leads to enhanced warming of the ice body. This increased warming then drives even more melting, creating more lakes, thereby accelerating the cycle. This positive feedback mechanism amplifies the rate of mass loss far beyond what would occur from simple warming alone.

Illustration 3: Supraglacial Lakes and the Albedo Feedback Loop

The result is a rapid reduction in the ice sheet's size and volume, with the lost mass inevitably flowing to the oceans and contributing to global sea level rise.

Resource: Based on an article by David Rippin: https://www.futurelearn.com/info/courses/tackling-environmental-challenges/0/steps/113613 

Further resources: https://www.livescience.com/51070-greenland-supraglacial-lakes-photos.html