Greenland’s ice sheet has been experiencing a disturbing acceleration in its rate of melting in recent decades, resulting in a significant rise in sea level. Among the remaining glaciers with a floating tongue, one particular glacier, Nioghalvfjerdsbrae (79NG), has become the center of attention in a new study published in The Cryosphere. The study, conducted by Dr. Ole Zeising from Alfred Wegener Institute at the Helmholtz Center for Polar and Marine Research, Germany, and his colleagues, utilized a combination of remote sensing, airborne measurements, and ground-level observations to investigate the effects of climate change on the decline of this ice tongue.
The research findings show that the ice tongue of the Nioghalvfjerdsbrae glacier has thinned by an alarming 42% since 1998, with an average loss of 38 meters of ice thickness since 2018. The scientists attribute this significant decline to the increasing ocean temperatures that have brought warmer currents into the area, resulting in enhanced melting and glacier retreat. Airborne radar images generated since 2010 have revealed the presence of a subglacial channel beneath the glacier, eroded by the inflow of warmer Atlantic intermediate water. This subglacial melting has caused the overall glacier surface to lower by 7.6 meters per year, with meltwater flowing rapidly at a rate of 150 meters per year during the summer months.
The Atlantic intermediate water carries dense saline water to the base of the glacier, where it flows into the cavity and warms the surrounding ice, triggering melting. The resulting buoyant meltwater then flows even further up into the subglacial cavity, intensifying the melting process and contributing to the formation of distributary subglacial channels. These channels further enhance the melting of the glacier’s base. The accumulation of warm water masses in the cavity has reached a thickness of 140 meters, exacerbating the vulnerability of the surrounding ice. This subglacial melting has also led to noticeable cracks forming at the calving front of the glacier, potentially signaling the impending disintegration of the glacier and worsening its retreat.
The researchers have also observed that increased summer melting of the glacier correlates with warmer atmospheric temperatures associated with global warming. Since 2005, the temperature has exceeded 0°C for approximately 50% of the time over a 70-kilometer section of the glacier, leading to surface melt during summer months. These enhanced meltwater rates and volumes contribute further to the overall degradation of the glacier. Additionally, the researchers discovered that the glacier’s surface has lowered by approximately 57 meters in a specific location since 2010. The ice thickness remaining above the subglacial channel is only 190 meters, amounting to 30% of the surrounding ice thickness. This highlights the susceptibility of the glacier to melting both above and below.
As the consequences of climate change persist, the melting of Greenland’s ice sheet will continue, rendering polar regions increasingly vulnerable to the effects of warming oceans. Ice albedo feedbacks play a significant role in this process. As white ice melts, more of the dark land beneath is exposed to solar radiation, resulting in increased absorption of heat and further melting of the neighboring snow. This exposes even more dark surface area, creating an ongoing cycle of heat absorption and melting. The analogy of wearing black clothing in summer versus white clothing, where black clothing retains more heat, is apt in understanding this feedback process. The effects of ice albedo feedbacks coupled with continued warming throughout the century may alter the current course of melting and lead to more rapid and extensive ice loss.
The ongoing melting of Greenland’s ice sheet, exemplified by the decline of the Nioghalvfjerdsbrae glacier, underscores the urgent need for immediate action to combat climate change. Rising ocean temperatures, intensified by global warming, continue to contribute to the accelerated melting and retreat of glaciers. The consequences of this process are far-reaching, affecting not only the melting of ice sheets and rising sea levels but also the fragile ecosystems and habitats of countless species that call polar regions their home. Urgent efforts must be made to mitigate the impact of climate change and preserve these vital environments for future generations.