Lake Brownworth

Here are a couple more pictures from the trip the the Wright Valley yesterday. We hiked to Lake Brownworth, a pro-glacial lake on the margin of the Wright Lower Glacier. Most of the lakes in the dry valleys are closed-basin lakes, meaning that water flows in, but it doesn't flow out. Lake Brownworth is different because meltwater from the glacier flows in, but the lake is drained by the Onyx River, the longest river in Antarctica. As I mentioned in my previous post, the Onyx flows away from the coast inland to Lake Vanda, which is a closed-basin lake. Lake Brownworth has a permanent ice cover like most of the lakes in the dry valleys. It also appears to have a significant amount of algal mat. You can see dark chunks of this mat material that worked its way up through the ice over many years and is still frozen to the surface. We were optimistic as we walked closer that the dark material might be wind-blown sediment, but as we got to the shore we could see that it was all algae. Because Lake Brownworth has a river draining it, the lake level must stay fairly constant. I mean, the lake level could drop, but it can't get any higher because of the river. There is a bathtub ring of algal mat marking the perimeter of the lake.