You wouldn’t generally think of ocean temperatures in the range of 40 to 50 degrees Fahrenheit (5 to 10 degrees Celsius) as hot. But to the great sea-fronting glaciers of Greenland it may as well be boiling.
Greenland Ice Sheet in Hot Water
All it takes is 32 degree F (0 C) water to begin melting the ice. And for each 1 degree increase above that margin, melt rates will dramatically ramp higher. Though a typical summer will push ice to melt at the Greenland seafront ice edge, this year, especially near Baffin Bay, the melt pressure has been extraordinary.
Ever since late June, 40-50 degree F sea surface temperatures have dominated the ice edge zone. For most regions that’s temperatures in the range of 4-11 degrees Fahrenheit (2-6 C) above average. The kind of heat that really risks a rapid melt along the ice margin.
(Sunday, August 16 sea surface temperature anomalies as provided by NOAA.)
A latent heat that sits at the surface, gnawing away at the ice, waiting for a fresh water flood. And when the fresh water does come, that hotter, saltier, heavier water is forced downward beneath the lighter fresh water outflow. At this point, the hotter waters are locked below the surface where they go to work eating away at the glacier base. Notably, the only region within Baffin Bay where we currently see cooler surface water is in the major glacier melt zone near Jakobshavn. It’s an indication that ice melt from a major glacier outflow there is cooling the surface waters even as it pulls the surface heat downward and toward the glacial base.
This glacial melt heat conveyor is the kind of process we are seeing more and more frequently near the great ice sheets as fossil fuel industry has continued its harmful emissions. And, it’s a process that, this week took a huge chunk out of one of the world’s fastest moving ice masses.
Huge Chunk of Jakobshavn Breaks Off
According to reports from The Arctic Ice Blog, the Jakobshavn glacier sent its biggest chunk of ice on record floating off into Baffin on August 16 of 2015. For a glacier that drains 6.5 percent of the Greenland Ice Sheet and that has been known to release icebergs the size of Lower Manhattan, that’s really saying something.
You can see this amazing and rather chilling calving event in action in the August 14 to August 16 satellite imagery comparison developed by Espen Olsen below:
(Jakobshavn experiences what is likely it’s largest calving event yet on Sunday, August 16, 2015. Image source: Espen Olson.)
Here we see the ice-choked Baffin Bay waters rapidly surging inland and taking up more of the Jakobshavn’s traditional outflow channel. What we do not see in this image, but what clearly happened, was that an ice mass hundreds of meters tall and covering an area of about 12.5 square kilometers was shattered into flinders as warming ocean waters invaded the Greenland Ice Sheet. Waters that will deliver still more heat to the ice. Waters that seek for the very heart of Greenland — a below sea level basin topped with 2-3 kilometer tall mountains of ice.
Back in the 19th Century, the Jakobshavn Fjord was half full of grounded Greenland ice. A long tongue of the glacier extended on outward through the channel. As of 2015, the Fjord is now completely full of water and ocean-bound ice bergs. The ocean itself has begun to invade the much larger ice masses beyond the Fjord. The broader inland mass of the Jakobshavn Glacier which is now directly in contact with the rising seas (indicated as Jakobshavn Isbrae on the maps above and below).
(Warming waters from Baffin Bay have driven through the ice in the Jakobshavn Fjord and are now boring into the thicker ice masses of Jakobshavn Ibrae. An impact that has serious implications for global sea level rise. Image source: The Arctic Sea Ice Blog and Espen Olsen.)
The inland-retreating Isbrae itself is a vast field of giant ice sheets. Massive tilting escarpments of luminous ice that, in the current age of fossil fuel forced warming, often cup great 1-3 kilometer long melt ponds in their wildly varied topography. It’s a single region that, in total, may hold about 1.5 feet of global sea level rise locked away in a rapidly melting ice pack. And Jakobshavn is just one of many regions (together containing about 15-20 feet worth of sea level rise) that are currently undergoing rapid melt due to the invasions of warming ocean waters.