Jakobshavn Glacier Second Calving ?

The calving front of Jakobshavn glacier has retreated dramatically since about 1850, to the point that the two main outflow ice streams can be seen as separate calving fronts, Jakobshavn North and South.

Jakobshavn North recently calved a large floe which was widely reported by Arctic watchers and then picked up by the news media - and hyped up. 

For a non-hyped report I recommend http://neven1.typepad.com/blog/.../jakobshavn...

Jakobshavn South appears to have recently calved a similar amount also, some time between the 10th and 16th of July 2010.

The jakobshavn Glacier lies about the midpoint of Greenland's west coast.  It is famous for its iceberg production and is quite a tourist attraction.  Bergs often ground after calving so that the fjord is pretty much choked with bergs and bergy bits which make their way slowly to Baffin Bay where they are released into the sea.  They are then swept north by a current which carries them up one side of Baffin Bay and down the other.

The first animation below shows general activity in the region.

Jakobshavn July 2 and July 5 2010

The sediment in the channel at left settles and / or is flushed away by meltwater.  In the middle of the main channel ice becomes more open.  It appears to me that a surge of meltwater has pushed ice around.  Some ice is pushed back up-channel towards the calving fronts.  The appearance of motion at the calving fronts is almost certainly an artifact due to image distortion.


Jakobshavn July 6 and July 7 2010

At some time during July 6 and July 7 a large amount of ice calved from the J North calving front.  Such a large amount of ice calving into open water in a fjord would have sent a wave along the whole length of the fjord.  Here, that surge appears damped by the masses of floating ice.  A surge of surface ice can clearly be seen as movements of grey patches.  Those patches are most likely large tabular bergs with moraine and rifts on top.

The surge continues across the more open ice and continues almost to the sea, as can be seen from the small grey patch moving near the berg outlet area.


Jakobshavn July 10 and July 16 2010

Between July 10 and July 16 2010 the area was very cloudy.  At some time between those dates a large area appears to have calved from Jakobshavn South.  Note that these images show less distortion near the calving front, which tends to confirm that the apparent calving is not an artifact of image processing.


Jakobshavn July 10, 11 and 16 2010

The cloud coincides with the appearance of calving, as does a surge of floes similar to the previous one.  That would set the calving date as July 11 2010.

For the reasons given, I am confident that these images from http://rapidfire.sci.gsfc.nasa.gov/ show a second calving event at the Jakobshavn Glacier's calving front.

Related reading:

Sermeq Kujalleq - Jakobshavn Isbrae Retreat

Iceberg Alley And Global Warming

The ChatterBox Arctic Index