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Friday, 19 July 2013

Nordvest Fjord, East Greenland

Satellite image of Nordvest Fjord and Scoresby Sund -- from Google Earth.

I've been doing some research recently on East Greenland, and have become more and more impressed with the statistics concerning Nordvest Fjord.

(Mind you, I have been obsessed with this particular fjord since 1962, when I paddled along the eastern fjord wall between Nordostbugt and the Oxford Gletscher outlet, with three fellow members of the OU East Greenland Expedition.  That was pretty mad, since we were using canvas kayaks to paddle through areas of brash ice -- if the canvas had been ripped in contact with sharp ice fragments, that would have been curtains.  One doesn't survive for more than a few minutes in water that cold....)

 A mixture of icebergs, old sea ice, new sea ice and brash ice fragments in Nordvest Fjord.  The new sea ice can start to form in late August, when it freezes at night.  It is not surprising that there has been no proper bathymetric survey of the fjord, and that all we have are occasional soundings.


And since you ask,  yes, we named the glacier, on which we did the first serious glaciological work in August 1962.

For maps of the territory in question, have a look here:
http://www.geus.dk/geuspage-dk.htm?http://www.geus.dk/program-areas/raw-materials-greenl-map/greenland/gr-map/sheet_s12-dk.htm

Back to the fjord, which is really the mother and father of all the fjords on Planet Earth.   If you go to any of the fjord sites on the web, you will find copious amounts of information about Sognefjord, Milford Sound, the fjords of Chile and even Antarctica, but very little about this one.  Strange, given that it is now well known from satellite imagery, even if not very frequently visited.  That's because access is very difficult.  The fjord extends c 217 miles (350 km) inland from the outer coast.  It's in two sections -- the outer (very broad) part is called Scoresby Sund, which is about 20 miles wide and 120 miles long, with Jameson land to the north and Milne Land and Knud Rasmussens land to the south and west, and then Nordvest Fjord proper, which pushes inland for a further 95 miles or so.  In this section the fjord is mostly less than 5 miles wide, and in places as narrow as 3.5 miles from shore to shore.  Access into the fjord system is often very difficult, even for ice-strengthened ships in the summer, because of the thick pack ice which conjests the Scoresby Sund entrance; in some years no vessels manage to get through it, and even when access is possible, the fjord is effectively shut off again early in September.

 This photo was taken near Nordost Bugt, where the narrow Nordvest Fjord opens out into Hall Bredning.  The snow-capped peaks and icefields on  the mountains across the fjord are typical of the fjord landscape.

The Nordvest Fjord - Scoresby Sund system has clearly been one of the major outlet routes for ice from the Greenland Ice Sheet, during the whole of the Pleistocene and maybe for much longer than that.  Even today the Daugaard Jensens Gletscher, near the head of the fjord, is possibly the most productive glacier in the whole of Greenland.  Because the ice here has been streaming so effectively in a narrow and constrained trough, the rate of downcutting has been impressive indeed. There are no proper bathymetric charts, but from the scattered soundings that have been made we see depths of 1372m, 1459m, 1372m, 1150m, 1237m, and 1290m between Eskimo Bugt and Syd Kap.  The deepest sounding of all is 1508m (4,947 ft).    These soundings show that the fjord is substantially deeper than Sognefjord in Norway (maximum known depth 1308m), which has just one short stretch deeper than 1200m.  But here on the flanks of Nordvest Fjord the plateau ice caps and mountain summits are almost all over 2000m (6561 ft), whereas there is little land over 1600m on the flanks of Sognefjord.  So the full depth of Nordvest Fjord over a distance of about 80 miles is approx 3300m or 11,000 feet.  I'll let somebody else work out how much material has been eroded and removed by ice from a trough of this size.......  but it is indisputable that this is the deepest, longest and most dramatic fjord system on earth.

We don't know enough about the long profile to know whether it conforms to the "ideal" long profile of Sognefjord, where we can see an incremental deepening of the trough wherever there have been supplements to the ice discharge via tributary glaciers:

I would expect something similar in the case of Nordvest Fjord.  What we do know is that where the narrow Nordvest Fjord opens out in the vicinity of Syd Kap and the Bear Islands, there is a sudden shallowing of the water, as the bedrock floor rises to approx 400-500m below sea level.  This is very similar to the situation at the mouth of Sognefjord, where ice diffluence has been associated with a reduction in erosive capacity, as we can see on the diagram above.  We don't exactly see skerries at the junction between the deep fjord and the shallow fjord, but there are some grounds and small islets which make navigation difficult and dangerous, and as in the case of Sognefjord the fjord bed rises from c 1200m to just a few tens of metres over a distance of just 4 miles.  This is called the threshold, and it explains why there is relatively little water exchange in the murky depths of the fjord; vast quantities of water are simply trapped in what is in effect a gigantic elongated basin.

Autumn colours at Syd Kap, where the fjord opens out into the wide expanse of Hall Bredning.
 
The uplands and icefields of Renland, with icebergs and the Bear Islands in the foreground.

Big tabular bergs in Scoresby Sund -- probably from either Daugaard Jensens Gletscher or one of the other ice sheet outlet glaciers.

Ice-smoothed slabs in Syd Kap Bay, with the waters of Hall Bredning beyond.

4 comments:

Anonymous said...

some beautiful photos there Brian!
PeteG

BRIAN JOHN said...

Not mine, I fear, Pete -- from my collection, picked up from all over the place. Full acknowledgement to Arctic Photo, Wikimedia Commons etc etc.....

snizan said...

yes - beautiful photos - but not made by brian - just stolen from commons. you should learn how to properly cite fotos from wikipedia. otherwise you may run into severe problems. sn.

BRIAN JOHN said...

Thanks Snizan. As I have indicated, the pics are not mine. They are not "stolen" from the commons -- those who place their pics on the commons assume they will be used. Where I know sources, I cite them. Mostly, I don't know where pics have come from -- I often pick them up third or fourth hand! See my post "on illustrations" -- it explains my policy. If anybody ever asks me to remove a pic, I will gladly do so. My photos are freely available for anybody to use, and I hope the source will be cited. But life is too short to check every usage!