New sites, new seals

Cuteness alert: this post will contain pictures of adorable baby seals

We wanted to explore some different sites yesterday to see if the chemical bromoform distribution throughout the sea ice is different. If we find something markedly different, we could sample for biology as well to try to better understand how chemistry and biology intersect in the ice. We worked with the field safety team to identify an area near Razorback, past the Erebus Glacier Tongue, that has been snow free, which means that the ice has more light exposure than at our normal, snow-covered site.

The sea ice at this location was 2 m 74 cm (just under 9 ft) thick and was a beautiful, glacial blue.

The edge of the Erebus Glacier Tongue (EGT). You can see Mt Erebus among the clouds behind the EGT.

Razorback

The apple: a perfect lunch spot

Driving over the snow-free ice was much noisier than on the snow because of the sleds dragging over a harder surface. We also had to stop multiple times to measure sea ice cracks and make sure the ice was thick enough to cross safely. The dynamic ice in this area means that there are openings for seal holes and Razorback was surrounded by Weddell seals, many of which have been tagged already by the seal team from Montana State. Since this area is along the regular seal team route, there was also a seasonal shelter - called an apple - and a refueling station for the seal team's snow mobiles.

You can kind of gauge how old the pups are by the size of the pup and of the mom. The pup in the picture of the very large mom calling to her pup is very young: it is tiny and the mother is still huge. Mother seals will lose a huge amount of their body weight during the weeks of intense pup rearing since they are not eating much/at all and are providing fat-rich milk to their pup. There were also a lot of skuas at Razorback. Skuas are scavenger birds and were probably feeding on pieces of seal placenta, and even seal feces, scattered on the ice.

Mother seal calling to her new pup. We couldn't get too close to the seals, especially the moms and pups.

Thick seal blubber makes even sea ice a cozy place for a nap. You can see that these pups are bigger and the moms are smaller.

Skua

We are used to silent days on the ice, but the seals were very noisy and it sounded like people were yelling in the distance.

We noticed an interesting starburst patterns all across the ice surface. None of us knew what it was, but we happened to be at a glaciologist's birthday party last night and Sridhar from Penn State explained to us that these are likely caused by small, localized melting. Dust can accumulate on the sea ice surface in certain areas, make the sea ice less reflective (lower its albedo). This will lead to small areas of meltwater just below the ice surface and the starburst is the meltwater moving through the ice.

Sea ice cracks and pressure ridge

We wanted to see if a relatively new crack, with newer, thinner ice, might be another good sampling location so we stopped by on our way back to McMurdo. The crack has slammed back together, forming a pressure ridge. Again, a good area for seal holes so the entire site was covered in seal poop. This would not make for good bacterial community sampling, which is a huge part of our project, so we abandoned the idea of sampling the new ice in the crack.

Pressure ridge