Tuesday, July 9, 2019

Visiting the Greenland Ice Sheet

The Greenland ice sheet is the second largest body of ice in the world, after the Antarctic ice sheet. It covers about 80% of the surface of Greenland, about 660,000 square miles. From north to south, it is almost 1,500 miles long, and is 680 miles wide at its greatest width. It is generally more than 1.2 miles deep and 1.9 miles deep at its thickest point. The mean altitude of the ice is an amazing 7,005 feet. It has two north-south elongated domes or ridges. The southern dome, at latitudes 63 degrees to 65 degrees N, reaches almost 10,000 feet in elevation. The northern dome, at latitude 72 degree N, reaches about 10,800 feet in elevation. If all of the ice were to melt, it would result in a global sea rise of 24 feet. 
The Greenland ice sheet, from Wikipedia. 
Another view of it from here
Kangerlussuaq, a Greenlandic name meaning "Big Fjord," or Sondre Stromfjord in Danish, is one of the most inland settlements in Greenland, at the head (upper end) of the fjord having the same name. It is 75 miles inland from Sisimiut which is on the coast. Kangerlussuaq is only about 16 miles from the Greenland ice sheet, making it one of the best places to access it.  
Map from here
An August 24, 2014 article by Mia Bennett, titled "Greenland: The road to the ice", found here, details some of the background about development of a road from Kangerlussuaq to the ice sheet. She points out it is the only place in Greenland you can walk onto the ice sheet. The 18.6 mile long dirt road was completed in 2001 by a car company wanting to test new cars on the ice sheet. That project was abandoned, but the road, the longest in Greenland, now allows access to the interior. 

We arranged for a guided tour to the ice sheet on a gigantic four-wheel drive vehicle along the gut-busting and kidney-wrenching rutted dirt road. 
We started about 7:30 p.m. and did not get back until nearly 1:00 a.m. We were confined in this huge vehicle for most of the time and photographs from within were virtually impossible because of the constant jarring. On several occasions audible groans filled the air as our torsos were ejected from our seats, then rocketed back quite indelicately. 

We kept seeing glaciers from the window of our vehicle and I kept wondering, is that the ice sheet? 
This glacier fed river is dry in the winter. Note the glacier in the background. 
More glaciers in the background.
A glacial waterfall.
A massive expanse of ice in the distance. 

A moraine in the foreground left by the retreating glacier.
That raised the question, what is the difference between the ice sheet and a glacier? The answer I got is "there is no difference." An ice sheet is what the linked article describes as a continental glacier. The Wikipedia article Glacier morphology describes an ice sheet as the largest form of glacial formation - a continent sized ice mass covering more than 50,000 km. They are dome shaped and have a radial flow of ice. There are two presently, the Antarctic ice sheet and the Greenland ice sheet. They cover one-tenth of our planet, but covered one-third during the Pleistocene epoch which lasted from 2,588,000 to 11,700 years ago. 

An ice stream is another type of glacier, although part of the ice sheet. It is a region of an ice sheet that moves significantly faster than the surrounding ice. Ice streams are significant features in Antarctica where they account for most of the ice leaving the ice sheet. The speed of an ice stream can be over 3,000 feet a year and the forces at the edge of the ice stream cause deformation and recrystallization of the ice, making it softer. Crevasses form in these regions. Most ice streams have water at their base which lubricate the flow. We visited the largest ice stream in Greenland, Illulissat Glacier, also known as Jakobshavn Glacier (Sermeq Kujalleq in Greenlandic). Ilulissat Glacier drains 6.5% of the Greenland ice sheet and produces 10% of the icebergs, 35 billion tonnes each year. In 2014, Illulissat Glacier sped up its rate to three times faster than it was in the 1990s, to more than ten miles a year. The end of the glacier is over a deep gouge in the bedrock which is 4,300 feet below sea level. This gives the glacier a "very large nozzle to flow out of." 

An outlet glacier originates from ice sheets and ice caps. They move in one direction determined by the underlying landscape. Outlet glaciers drain inland glaciers through gaps found in the topography. Ilulissat Glacier is also an outlet glacier. So to get back to the point of the difference between an ice sheet and a glacier, Ilulissat Glacier is part of the ice sheet, is an ice stream and also an outlet glacier. 

I'm not sure why our road which followed a circuitous route near a number of glaciers on the way up did not stop at them. My best guess is that we were going up in altitude and actually getting on the ice sheet in an area where it was more stable (not calving and without crevasses). 

We finally arrived at the ice sheet and found it windy, very cold, and looking more like an industrial waste site. 

In a blog post titled, "When Glaciers Get Dirty: Attack of the Cryoconites," I learn that the blackness we saw covering much of the ice sheet is cryoconite, a "powdery windblown dust made of a combination of small rock particles, soot and bacteria." More specifically, it is a combination of  "mineral dust from warmer regions of the world, rock particles from volcanic eruptions,...soot from fires, the emissions of our cars, and coal-fired power plants." [By the way, note the very cool photo of Birthday Canyon in the Greenland ice sheet which is part of the post]. 
Judy, bundled up for the cold with the expanse of the ice sheet behind her.

Judy photographing me as I photograph her.
The ice is very crystally and gritty. As we walked we heard the constant "crunch, crunch" of our feet, like walking on Hawaiian shave-ice. The grit offered some traction, but only to some extent. Any substantial incline proferred the opportunity for a tumble on one's gluteous maximus and a hard, sliding fall on the grit would likely result in some "road rash." Crampons would make walking on the ice much easier. 
This close-up reveals the ice-grit. 
Some members of our group have expressed some dissatisfaction with this trip to the interior, much of it attributable to the discomfort of the ride and I think also somewhat attributable to our lack of preparation for the extreme cold we found there, particularly because when we left Kangerlussuaq it was uncomfortably hot. I agree that it was far from our best activity in Greenland, but I felt like it helped me understand Greenland much better and I'm very glad we did it. 

1 comment:

  1. Had we not had this experience, we really wouldn't have experienced Greenland. How can you not go to the ice cap when it covers most of the country? Yes, the vehicle we rode in was downright ridiculous, but it's not like there are a ton of options and/or resources. Good heavens, we were in GREENLAND.