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Author Topic: Petermann Gletscher / Petermann Fjord / North West Greenland  (Read 308951 times)

BornFromTheVoid

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #750 on: August 18, 2020, 11:19:57 AM »
Hmm, IDK, Samuel. Is it sea ice thawing or crack opening what we see in your GIF?

In the zoomed in direct comparison i don't see the crack growing really.

I aligned the southern part so as to highlight the gap growth.
Doesn't seem like much, but it's close to 20 m growth on the northern section here
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

blumenkraft

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #751 on: August 18, 2020, 11:48:11 AM »
Right, the gap on that side widened a bit. I agree.

(Great alignment job there, BTW ;) )

Tor Bejnar

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Re: Petermann Gletscher / Petermann Fjord / North West Greenland
« Reply #752 on: August 26, 2020, 06:57:04 PM »
Seasonal evolution of supraglacial lakes on a floating ice tongue, Petermann Glacier, Greenland

by Grant J. Macdonald, Alison F. Banwell and Douglas R. MacAyeal
 Annals of Glaciology, Volume 59, Issue 76pt1  -  July 2018
Quote
Abstract

Supraglacial lakes [SGLs] are known to trigger Antarctic ice-shelf instability and break-up. However, to date, no study has focused on lakes on Greenland's floating termini. Here, we apply lake boundary/area and depth algorithms to Landsat 8 imagery to analyse the inter- and intraseasonal evolution of supraglacial lakes across Petermann Glacier's (81°N) floating tongue from 2014 to 2016, while also comparing these lakes to those on the grounded ice. Lakes start to fill in June and quickly peak in total number, volume and area in late June/early July in response to increases in air temperatures. However, through July and August, total lake number, volume and area all decline, despite sustained high temperatures. These observations may be explained by the transportation of meltwater into the ocean by a river, and by lake drainage events on the floating tongue. Further, as mean lake depth remains relatively constant during this time, we suggest that a large proportion of the lakes that drain, do so completely, likely by rapid hydrofracture. The mean areas of lakes on the tongue are only ~20% of those on the grounded ice and exhibit lower variability in maximum and mean depth, differences likely attributable to the contrasting formation processes of lakes in each environment.
The paper's conclusions end with
Quote
...
Based on previous studies of SGLs on Antarctic ice shelves, the presence of SGLs on Petermann's floating tongue may be indicative of its vulnerability to instability and potential collapse (e.g. Scambos and others, 2000, 2003; Banwell and others, 2013). We find lakes to cover <2.8% of the total surface area of Petermann's tongue, compared with the 5.3% of Larsen B's area that was covered prior to its collapse in 2002 (Banwell and others, 2014). Predicted future rises in air temperature (Kirtman and others, 2013) could enable a higher density of lakes, with larger volumes, to develop from earlier in the season, possibly leading to increased ice tongue instability. However, the decline of SGLs through July and August in each year studied, despite sustained high temperatures during those months, suggests that evacuation of meltwater from the tongue (e.g. by a river cf. Bell and others, 2017) may limit the total volumes of meltwater storage on Petermann's floating tongue, thereby mitigating the risk of instability and break-up.

(I found the article because I was looking for natural "hydrofracking" events being reported.  I had mis-read an ASLR comment a few days ago...)

I know this paper is a couple years old, but I don't recall reading about it before ... 

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