Charcot Island

(This post has been changed from the original version. Photos that were not taken by us have been removed and a new map of Charcot Island was added)

 

Charcot Island

 

As the Antarctic Peninsula continues to warm at an alarming rate, the sea ice has been retreating further south, creating a climate similar to what is seen in the Sub-Antarctic. In an effort to follow this transition, this year the LTER cruise was traveling farther south than in previous years, with our final destination being Charcot Island at 69ºS. At Charcot, we hoped to find this retreating sea ice and locate an Adelie penguin colony that had last been surveyed by air in the 1980s. 

Alex & I on the bridge of the ship with Charcot in the background

Rather quickly, our question about finding sea ice was answered. The ship was soon surrounded by large flat pieces of ice, indicative of sea ice rather than icebergs. Sea ice is formed by freezing seawater, while icebergs are fresh water that have broken free from nearby glaciers or ice shelves. You’ll find both of these forms of ice in the Charcot area, as the well known Wilkins Ice Shelf has been breaking up rapidly in recent years, and it currenlty covers much of Charcot Island. The next big question was whether we would find any Adelie penguins still breeding on the island. Another question was whether the birders would be able to negotiate around all the ice in a zodiac and get to land. 

A lone penguin spotted on the way into Charcot Island

A tabular iceberg dwarfing the Gould

Kristin & I in front of one of the massive tabular bergs

Alex & I were able to join Kristin and Rick (the birders) on their first attempt to the island. The ship could only take us within about 1.5 miles of the island and then we had to zodiac it from there. Unfortunately, we weren’t able to get much closer to the island due to the enormous amount of sea ice and the monstorous tabular icebergs that were blocking our way. But in our attempt to reach the island we did spot a penguin colony from afar. At first, we all doubted Rick’s claims that he saw guano (penguin poop) covered rocks and penguins amongst the rocks. However, as we were able to get a touch closer and using binoculars, we all finally agreed that there were most certainly guano covered rocks and definitely penguins! Ice conditions prevented us from getting any closer but at least we could answer the question that yes, there is a colony of penguins on Charcot Island. 

Penguin colony on Charcot from afar

The pink tinge on the rocks was how Rick originally spotted the penguins and if you zoom in even more on this photo you can see vague black and white shapes that resemble penguins. Luckily, we had a few more days to spend in this area, so a second, more successful attempt was made to get the birders to Charcot. They were able to land and confirm the presence of breeding Adelie penguins, about 50 breeding pairs.

This is a map of Charcot Island showing where the Wilkins Ice Shelf connects to the island. This map came from the Secretariat of the Antarctic Treaty and is available from their website. Below you can see an enlargement of the area where penguins were originally reported in 1976. The colony we located on Charcot was in this same area.

Kristin and Rick managed to hike up to the penguins that had made their nests on a very steep rock ledge. They spent a few hours weighing chicks and tagging a few adults birds with tracking devices so that we can monitor where they are foraging and where they end up at the end of the breeding season.

At first glance it seems an especially harsh place for these penguins to be breeding. However, earlier in the day while approaching the island we discovered a polynya. A polynya is an area of open water surrounded by sea ice and indicative of warm water upwelling. The polynya can be seen on the map above, it is the small bay just below the penguin colony. As we entered this polynya the bottom dropped from 150 to 550 meters. This meant we had discovered an underwater canyon that was likely providing the warm water upwelling, which not only maintains the polynya but also drives phytoplankton and krill production in the area. Krill being the primary source of food for the Adelie penguins. These underwater canyons are also found near Palmer Station and off Avian Island. These areas are where the Adelie penguins are known to forage and where we sent our glider to collect data from the water column. Bill Fraser (PI for bird and upper trophic levels of the LTER) has a hypothesis that wherever you find these underwater canyons you’ll find breeding Adelie colonies nearby. The breeding Adelie colonies on Charcot seemed to fit this hypothesis perfectly. 

Charcot Island