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Kullorsuaq

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Local Fjords

Leveraging Local Knowledge to Measure Greenland Fjords

 
 

 

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Alison Glacier

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Polar Geophysics Group

Lamont-Doherty Earth Observatory

 

 

Alison Glacier Background

Alison

Alison glacier is shown circled above. The left image is a velocity map showing Alison flowing at up to 3000 m annually from 2005/2006. The image on the right shows change in speed from 2000 to 2006 while the red dot shows the amount of glacial retreat in that period. Click on the image to enlarge (image from Joughin et al, 2010)

Our research will focus on the ocean interface at Alison glacier ( 74.37 N and 56.08 W). Alison empties into Melville Bay to the east of Kullorsuaq Island and has been undergoing dramatic change over the last decade. Three methods for looking at glacial change are (1) to look at acceleration in the rate of ice flow that moves ice from land into the surrounding ocean, (2) to map rates of retreat of the glacier as it calves or melts away from the leading edge, shortening its length, and (3) to look at changes in elevation of the glacier.

(1) Acceleration: Using radar data Joughin et al. 2010 noted Alison glacier posted the fastest acceleration of glaciers north of Upernavik for the period 2000/1 to 2005/6 with peak speeds doubling in that period, and ice front moving at speeds of up to 3000m annually. During the same period adjacent glaciers around Hayes glacier to the north, actually slowed, pointing to a localized rather than a regional cause. Acceleration at tidewater glaciers has been linked to the loss of the floating glacial tongue. Warming ocean water has been linked to the weakening and break up of glacial tongues. As the tongue calves and breaks apart it releases back pressure on the flowing glacier, allowing it to surge forward, and as it flows it thins allowing it to accelerate even further.

 

 

Retreat of Alison tongue

Satellite images of Alison glacier retreat. Click on the image to enlarge.

(2) Retreat: Simultaneous to Alison's acceleration Joughin et al. 2010 noted the calving front significantly retreated by 8.7 km. Further studies by Howat and Eddy (2011 ) looked at a longer period, from 2000-2010 and noted that while 98% of the 71 northwest glaciers studied experienced retreat in this time, Alison's retreat far exceeded the average retreat. Alison glacier posted retreat rates of > 1km annually for the 2000-2010 period for a total of 11 km well in excess of the average 100m annual retreat for the total 2010 tidewater glaciers studied from throughout Greenland. Alison joined two other glaciers with this high retreat rate of >1km annually, Zachariae in the northeast and Jakobsahavn in the southwest. Warming water has also been linked to glacial retreat with warm water making its way to the glacier grounding line and causing melt and instability resulting in more calving and glacial retreat.

To the right is a time series of satellite imagery showing the retreat of the Alison glacier from 2001 to 2013. Alison is the glacier at the top flowing right to left as it moves ice off Greenland into Melville Bay. The sections of black that move through the image are caused by the rotation of the satellite. When looking at this series of images focus on the flowing section of the glacier, recognizable by the smooth streaked surface with a slight brown cast. As the years progress you will see the front of the ice break away into ice melange, or broken ice bits showing the glacial retreat. You might need to watch the images cycle through several times (using the enlarged version is helpful).

elevation loss

Image from Kjaer et al, 2012. The upper part of the image shows changes in elevation in Greenland's northwest coastal glaciers moving from north (left) to south (right) loss in elevation in meters. The bottom part of the image shows loss in length in km for the same period. Click on the image to enlarge.

(3) Elevation: Kjaer et al, 2012, compared aerial photographs along Greenland's northwest coast to measure changes in ice elevation in over the time periods 1985-1993 and 2005-2010. The glaciers are lined up geographically moving from north on the left to south on the right. Alison glacier is shown in the image with a red arrow. The top piece of the graph measures the significant drop in ice elevation, represented in meters of elevation change, in both 1985-2005 (in blue) and extending to 2010 (in green). The 'mirror image' below represents change in glacial length in km of loss for the same time periods.

Looking at the graphic it is evident that changes are more dramatic in the southwestern coast of Greenland, slowing as you move north. Ipernavik and Alison show the largest change in elevation.

 
       
   

LDEO

This project is funded through LDEO Climate Center with additional funding from NASA Interdisciplinary Program & logistical support from NSF. | contact us | web master

 

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