Never a dull moment, always something new to see and learn!
I'm eyeballing the Arctic sea ice graphs page several times a day and noticed something new the day before yesterday while eyeing the Arctic SST map from the National Centers for Environmental Prediction (NCEP), run by climate scientist and blogger Robert Grumbine (the sea ice and sea surface temperature groups, not NCEP itself):
It struck me that the river surface temperatures of some of the Russian rivers were anomalously high (as much as 8 degrees C in some places), which isn't that remarkable of course when you consider the air temperatures on that side of the world, which have been high for quite a while now:
The intruiging thing, when you think about it, is of course that the water of these warm Russian rivers eventually ends up in the seas on the Siberian Coast. Two of the rivers that light up red and crimson on the NCEP SST map, the Ob and the Yenisei, flow out into the Kara Sea. The third one, the Lena, empties into the Laptev Sea. What happens when that relatively warm, fresh water reaches the icy shores? Is there an effect on ice melt, now that the melting season has started?
This was the question that popped up in my head when I noticed some emerging red and orange in the Kara Sea on the DMI/COI SST anomaly map, right where the estuaries of the Ob and Yenisei are situated. There's a red and orange blob close to Severnaya Zemlya (which even had some pink in it yesterday), but I think that's some sort of artefact:
My intuition says it doesn't have a big effect on the whole (when compared to ocean currents or insolation for instance), but it's interesting nonetheless and could be a significant factor at the start of the melting season, while there is fast ice stuck to the coast and sea ice nearby.
And I'm not the only one speculating here, as there was another blogger last summer who asked the same question in relation to the massive heatwave in Siberia. Googling around some more I found a few hints here and there on the effect of warm river water. Such as this sequence in a book called Exploring Polar frontiers: A - L., Volume 1 by William James Mills:
His plan was to acquire a sturdy Norwegian sealer and sail it along the Northeast Passage to the Lena Delta. There, Toll said, the best dogs in the world could be obtained. Also,the comparatively warm river water would enable him to find open water leading north of the New Siberian Islands, hopefully to "Sannikov Land".
I found a few scattered clues on a web page called Russian Nature:
In the Laptev Sea, heat flux through weaknesses and leads in summer months exceeds the estimated heat input by river runoff by a factor of 2.5 (Zakharov, 1966).
The Yenisey and the Ob bring warmer water into the western Kara and accelerate ice melt.
In summer, the removal of old ice, heat gain by dark polynya areas and relatively warm river runoff accelerate ice melt, and most of the Laptev becomes ice-free as far as 77°N by mid-September (Barnett, 1991).
Gareth Renowden of the Hot Topic blog - one of those bloggers who is keeping his eye firmly on what is happening up there - had a piece called Dragging the River almost three years ago that was about our beloved methane bomb, but indirectly touches on warm rivers as well:
Now the anthropogenic warming of the northeast Siberian area have lead to increased river discharge and higher temperature on both river water and other costal water which could contribute to an accelerated erosion of the permafrost layer.
But I hit the jackpot when I found a paper that deals specifically with the influence of river discharge on the thawing of sea ice, by Dean et al. 1994 [PDF]. The research focuses on the MacKenzie Delta, which is on the other side of the pond, and the data is almost 25 years old, but there's a lot of information pertaining to the subject of this blog post. From the conclusion:
Ice melts offshore from rivers earlier than it does along coasts with minimal river discharge. In the case of the Mackenzie River, fast ice is removed two weeks earlier than along surrounding coasts where river discharge is minimal. However, the ice removal process starts two months earlier.
The melting of sea ice by arctic rivers involves three processes: initial flooding, absorption of solar radiation and heat provided by warm water discharged by the river. Offshore from the Mackenzie River channels, the albedo of the water that overflows the fast ice is as much as 1/7 that of sea ice values, and hence the water absorbs significantly more energy than ice-covered surfaces even after melt-ponds develop. This absorbed energy initiates the melting process offshore of river channels. In our study, the albedo values of pack ice decreased as much as 113 between May and August. Approximately two weeks after the overflows develop, sea surface temperatures offshore from the delta begin to rise as the volume of “warm” water discharged by the river peaks and becomes the dominant source of energy that melts fast ice.
During my seach I also discovered that there has been an increasing trend in river discharge - touched upon in the aforementioned Hot Topic article - to the Arctic Ocean from both Eurasia (over 1936-2008) and North America (over 1970-2008), according to the Arctic Report Card for 2010, suggesting that both rivers and sea ice were responding to changes in large-scale hemispheric climate patterns (Shiklomanov and Lammers, 2009 [PDF]):
I'm sure there has been more research into this (though most recent papers are pay-walled), with a focus on the added effect of Global Warming on the temperature of those 'warm' rivers. If anyone knows about this, please share quotes and links in the comments.
This is obviously one of the things that kicks off the melting season. I'm seeing it for the first time and will be giving some extra attention to the Siberian coast the coming weeks. Never a dull moment, always something new to see and learn!
Delta of the Lena river