Saturday, June 7, 2014

Rivers Contributing to Arctic Sea Ice Melt

I saw a very interesting paper in the journal Geophysical Research Letters about the MacKenzie River in Canada which empties into the Beaufort Sea and its affect on the melting of the Arctic sea ice, especially the massive 2012 ice melt. The waters in the river get warmed up and then empty into the sea, contributing to the sea warming and the ice melt. In 2012 this was complicated by a large ice dam that wasn't overwhelmed until 14 June. By 5 July, the authors found the surface temperature in the Beaufort Sea had increased by 6.5 degrees Celsius (about 11.5 degrees Fahrenheit) and the extent of open water occupied by warm waters had increased by 50%.

Their conclusion is that the MacKenzie and other large rivers bring large amounts of heat into the Arctic Ocean and contributes to melting sea ice.

So, what does that mean for today? Well, let's begin with the fact that Alaska and Siberia both had record warm winters. This means we could expect to see warm water flowing into the Arctic Ocean from those two regions. Canada had a cold winter, so the MacKenzie might not make much of a contribution in this regard this year. But, that a look at this data.

The graphic shown below is from the Polar Portal and shows the surface water temperature in the northern latitudes. This graphic shows the conditions on April 10 of this year. Notice the greenish area at about the 2:00 location. This is the discharge area of the Lena River, one of the largest rivers in the world. Notice how much warmer it is in that area than the surrounding areas. Also, note the greenish areas around the 4:00 position. This is the discharge area for the Ob and Yenisei Rivers. Again, note how it is warmer there. Now, using just this data here, we can't be sure about the Ob and Yenisei contributions. There are ways to explore that question, but not here. After all, that warming might be due to the Gulf Stream. But, that warming from the Lena River is very isolated and there is no discernible heat source that could be responsible for the warming except the river. In fact, if you were to follow this warming through the spring (I did), you would have seen the warming area spread outwards from the mouth of the river. That area is now mostly ice free.

An interesting point is to note the area around the mouth of the MacKenzie (about the 10:00 position) is not experiencing any above average warming. That is consistent with what I said above.

Source: Polar Portal
This bears watching. Right now, I would expect to see in coming weeks above average warming (and sea ice melting) in the area north of Siberia but average warming in the area north of western Canada.

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