Redoubt Lake

I went to a talk last night about sockeye salmon studies in Southeast Alaska. One of the few systems with sockeye that has much data on returns over the year is Redoubt Lake a few miles south of Sitka. Here are some interesting facts about the lake (some I learned from the talk and others that I learned elsewhere): Redoubt Lake is over 200 meters deep and below a certain depth it is saltwater. If you pull up some of the lower water it smells like sulfur (rotten eggs). Saltwater is more dense than freshwater and this prevents the lake from turning over and bringing up nutrients from the bottom. Redoubt is the largest of these lake types in Southeast Alaska. The lake is less than 15 feet above sea level, and I have read that on extreme high tides when there has been a significant storm surge, sea water has spilled into the lake. If sea level were a little bit higher, or the small barrier between the lake and the bay were removed, Redoubt Lake would be another fjord. If there has been significant isostatic rebound (where the ground raises back up after the weight of the glaciers has been removed), which seems likely, Redoubt Lake probably was a fjord at some point in the last few hundred or thousand years. In the late 1800’s and/or early 1900’s there were large runs (70,000 or more) of sockeye at the lake, however in recent decades runs have been much smaller.

I was somewhat surprised to find out that the lake was so deep (one person mentioned over 220 meters, another said 1000 feet, in either case, it’s deep). This leads me to wonder what might be at the bottom. I wonder what, if anything, lives at the bottom. How fast do things decompose down there? I think it would be interesting to explore the depths of the lake.

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