Jakobshavn Isbræ, West Greenland, which holds a 0.6 m sea level volume equivalent, has been speeding up and retreating since the late 1990s. Interpretation of its retreat has been hindered by difficulties in measuring its ice thickness with airborne radar depth sounders. Here we employ high-resolution, helicopter-borne gravity data from 2012 to reconstruct its bed elevation within 50 km of the ocean margin using a three-dimensional inversion constrained by fjord bathymetry data offshore and a mass conservation algorithm inland.
We find the glacier trough to be asymmetric and several 100 m deeper than estimated previously in the lower part. From 1996 to 2016, the grounding line migrated at 0.6 km/yr from 700 m to 1100 m depth. Upstream, the bed drops to 1600 m over 10 km then slowly climbs to 1200 m depth in 40 km.
Jakobshavn Isbræ will continue to retreat along a retrograde slope for decades to come.
The Polar Ocean Challenge team issued a press release last night. This is what it said:
The Polar Ocean Challenge successfully completed their quest to sail the North East Passage and North West Passage in one season. The North West Passage was completed in an astonishing 14 days due to the fact that it was almost totally ice free. They encountered ice only twice in their 1800 mile NW Passage part of the voyage. This highlights an extraordinary loss of sea ice in the Arctic in the 30 years that David Hempleman-Adams has been coming to the area. He said, ‘whilst we are all delighted to have succeeded, it is extremely worrying to see this lack of ice so starkly‘ The objective of the expedition was to raise awareness of the change in the fragile climate in the Arctic. They left Lancaster Sound at the end of the NW Passage at 19.18 UTC on 12th September and are headed for Greenland.
This seems likely to cause much gnashing of teeth in certain quarters, where it is claimed that:
The S/V NORTHABOUT has failed to cross the Pacific Ocean Arctic Circle in the Bering Strait as the official starting line to validate their Northwest Passage attempt. You cannot say you climbed Mount Everest by just reaching high camp – you must summit. You don’t ride a bicycle in the Tour de France without starting and finishing over the course in the designated places. Likewise, you must cross BOTH the Pacific Ocean Arctic Circle in the Bering Strait and the Atlantic Ocean Arctic Circle in Davis Strait to validate a Northwest Passage.
In Northabout’s defence I pointed out that:
Perhaps the Polar Ocean Challenge team have other priorities than gaining an entry on that particular list?
If you’re planning a single season circumnavigation a diversion via Provideniya or Nome doesn’t make a whole lot of sense, rules or no rules.
but nobody else seemed to take that view!
Today they also pointed out on their Twitter feed that they are a:
Pressing on the crew of Northabout are now approaching halfway across Baffin Bay:
Her crew are trying to reach Upernavik in Greenland before the impending storm gets too bad. Here’s our own WaveWatch III based forecast for tomorrow afternoon:
Today Tonight and Wednesday Wind light increasing to south 15 knots early this evening and to south 20 late this evening. Wind backing to southeast 25 overnight then diminishing to light Wednesday afternoon.
Waves
Today Tonight and Wednesday Seas 1 metre building to 2 after midnight.
Thursday
Wind light increasing to northwest 15 knots in the afternoon then veering to north 20 late in the day.
Friday
Wind north 30 knots diminishing to north 20.
I seem to recall that 30 knot winds are best avoided! After Upernavik Northabout will head for Nuuk further south in Greenland and then across the North Atlantic back to Bristol, where she started her voyage back in June. It is certainly not beyond the bounds of possibility that there will be winds of 30 knots and more to contend with on that final leg of the Polar Ocean Challenge!
[Edit – September 14th]
Northabout has obviously not managed to escape the storm entirely. Ben Edwards reports today:
I hate this part of a journey. Yesterday as I came off watch we were scheduled to arrive about midnight tonight. I hate that anyway because you get the so close yet so far feeling. But typically as I came off watch the wind picked up, moved to an unhelpful angle and created the worst sea state we’ve had since the Chuckchi Sea. We’re still supposed to arrive about two in the morning but it will make the next twenty two hours really horrible. Not that our arrival time mattes too much, we can’t go in till it’s light anyway.
Gale from south and southeast, 13 to 18 m/s. From the western part decreasing and becoming south and southwest, 5 to 10 m/s, in northern part locally 13 m/s. Thursday gradually in eastern part south and southeast, 8 to 13 m/s, but in western part cyclonic variable, up to 10 m/s. Especially in northern part locally rain, sleet or snow with moderate to poor visibility, otherwise good visibility.
Significant wave height: 3,5 m. Swells: 3 m.
Many icebergs and growlers in the eastern part along the coast, otherwise few icebergs and growlers.
Upernavik is slightly south of there, but nonetheless Ben will have a few more uncomfortable hours, and Northabout may yet meet some more ice before her crew set foot on dry land once again:
[Edit – September 15th]
Northabout has just arrived in Upernavik:
[Edit – September 16th]
It looks as though Northabout has just left Upernavik, and is now en route to Nuuk:
As we expected, it was a long night last night as the big swell and Northernly winds continued to sweep us along from Upernavik, big surf waves behind us breaking under us, Northabout became a little Hawwai five o. We made our way along the coastline through amazing beautiful icebergs created by glaciers at Ilulissat.
The icebergs were between the size of telly to the size of a house to the size of a grand hotel. They were breaking up, and once or twice right in front of us creating lots a small bergs and ice chunks that don’t float so high above the water and so are difficult to spot especially with a large 10 foot swell, they disappear and reappear in the water around us.
[Edit – September 19th]
Northabout has just left Ilulissat, en route for Nuuk:
[Edit – September 22nd]
Northabout has crossed the Arctic Circle and has just reached Nuuk, the capital of Greenland:
En route from Ilulissat her crew have seen some amazing sights:
As we reported back in February, the Jakobshavn Isbræ glacier in Western Greenland has already calved around about 7 km² of ice earlier this year. Now the eagle eyed Espen Olsen reports another large calving via the Arctic Sea Ice Forum:
Jakobshavn Isbræ the calving-machine is up in gear again
Here’s his evidence, an animation created using images from the Landsat 8 Operational Land Imager:
After a bit more graphical processing Espen subsequently posted another animation:
This one reveals the amount of ice that still needs to be lost before the calving face retreats as far as it ultimately did last summer. Espen also comments:
The calving front at Jakobshavn is very different to September 28 2014 (record retreat), not only did the glacier expand since then but the front is much narrower?
Here once again is Jason Box’s Jakobshavn calving summary from February:
Jakobshavn Isbræ is a glacier in Western Greenland made (more?) famous by James Balog in his “Chasing Ice” movie. Here’s the “official video”:
which claims that it:
Captures [the] largest glacier calving ever filmed. On May 28, 2008, Adam LeWinter and Director Jeff Orlowski filmed a historic breakup at the Ilulissat Glacier in Western Greenland.
Depending on which languages you prefer to mix and match “Ilulissat Glacier” is another name for the self same glacier. So is “Sermeq Kujalleq”. Now comes news that something similar has just happened, albeit captured only by satellites in the twilight of the Arctic “spring”. Over on the Arctic Sea Ice Forum Espen Olsen posted late last night (UTC):
Believe it or not! Massive calving seen at the southern branch of Jakobshavn Isbræ
together with this animation created using images from the Landsat 8 Operational Land Imager:
We’ve just grabbed this Sentinel-1A synthetic aperture radar image from February 15th 2015 via Polarview, which appears to suggest that the calving took place before 20:38 UTC on that date:
Here’s a Sentinel-1A image via “nukefix” at the Arctic Sea Ice Forum, which confirms that the calving took place on or before February 16th:
This is a before/after animation from “A-Team” on the Arctic Sea Ice Forum, using 15m resolution Landsat images:
Finally, for the moment at least, Espen Olsen provides an illustration of the retreat of the calving face of Jakobshavn Isbræ since 1851:
This most recent event does not bring the calving face further east than the position in summer 2014. However the sun’s rays are only just returning to that part of the planet, and the next one may well do so.
[Edit – 24/02/2015]
We’ve phoned DMI and NSIDC as well, but Jason Box who is a Professor at the Geological Survey of Denmark and Greenland has been the first to respond with an opinion about how unusual this event is:
It’s an interesting finding. In the attached prepared by Karina Hansen you will see a light yellow polygon illustrating the end of melt season 2014 ice. Jakobshavn front position retreated from the Feb 2014 (pink line) and Feb 2015 (green line) positions. The Feb 2014 and Feb 2015 positions are roughly the same with 2014 Feb being further retreated than Feb 2015:
A cautious response: even if this calving were abnormal, we will likely see an advance in the next weeks that will fill the void. Why?
A) This glacier flows fast, and
B) Now with less flow resistance there will likely be an acceleration making the void filling happen even faster.
Here are annual end of melt season area changes measured by PROMICE.org. These are being updated. I will ask Karina Hansen today to update for 2014 and 2015. We could have that result in a few hours.
1999/00
-2.750
2000/01
-2.473
2001/02
-16.357
2002/03
-45.617
2003/04
-21.235
2004/05
-10.015
2005/06
-4.151
2006/07
-3.830
2007/08
-3.202
2008/09
-2.174
2009/10
-8.725
2010/11
-6.693
2011/12
-13.743
2012/13
-2.826
In context of the ongoing retreat, I would speculate that this retreat could make further retreat more likely because the acceleration from B) would cause ‘dynamic thinning’ that through a positive feedback would reduce glacier bed friction facilitating further thinning and acceleration. This feedback is an amplifier and not runaway but being activated would precondition Jakobshavn glacier for further retreat.
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