Because it seemed like a good idea at the time....: Guiding the Pressure Ridges

Close to the Kiwi Base are beautiful and majestic ice formations shooting up from the surface of the sea ice. These are called Pressure Ridges and we find ourselves there a few times a week guiding other McMurdo residents through the eerie glacier turquoise behemoths of ice.

The Thumbs UP!

Pressure Ridges are formed between the forces exerted from the ice shelf on the more variable sea ice. The permanent ice shelf is actually a massive floating glacier on top of the sea. Some estimates we have heard is that the Ross Ice Shelf is about 1,000 feet thick. The sea ice is found closer to shore and is not permanent. This sea ice ebbs with the changing seasons and is currently 6 or 7 feet thick and will almost completely break up and melt by January. As the massive ice shelf exerts pressure on the sea ice it gives and forms fissures that shove ice up into ridges, thus called Pressure Ridges. This same force mimics how mountain ranges are born on a much faster and smaller scale. These ridges often have cracks in the vicinity due to the changing nature and thickness of the sea ice along with melt pools. The melt pools can be fresh water, salt water, or a brackish mix depending on if they are formed by the melting water off the ridges, fed from a crack leading to the sea, or a mix of both.

Walking among the pressure ridges is an eye opening experience when you consider it through the eyes of Antarctic history and Shackleton's Endurance expedition. Shackleton, on his third expedition to Antarctica, was attempting to land his ship the Endurance on the Antarctic Peninsula (closest to South America). He then was going to travel overland with dog sleds making it to the South Pole and continuing the traverse to arrive back at the Ross Sea, where McMurdo is currently located. He was planning on having a second crew land at Discovery Hut (Scott's hut from previous Antarctic expeditions and still standing next to McMurdo) and take a second team to stash food caches along the way for Shackleton to use to complete his traverse. Shackleton never made it that far and ran into horrible sea conditions unique to sea travel around Antarctica and especially the Weddell Sea. The formation of the Weddell Sea and the surrounding land masses created a dangerous situation. The pack ice trapped the boat between broken ice and icebergs. The Endurance was trapped in the pack ice for months and his crew lived in the boat. Once the end of winter came, the pressure exerted from the ice shelf on the sea ice caused pressure ridges, which eventually encapsulated the boat and destroyed it completely. Shackleton and the rest of his crew were forced to travel over the precarious pack ice dragging their smaller open boats and food on dog sleds over and around the pressure ridges. Navigation was difficult and the ridges of ice made travel slow and tedious. Walking among them today really makes you appreciate the adventure and determination it must have taken long ago Antarctic explorers on such a harsh and unforgiving continent.

Pretending to be on Shackleton's expedition

We don't have it quite so rough! We simply take a group of 10 to walk a flagged route and take pictures. The route is constantly changing due to new pressure ridges forming, cracks widening, and expanding melt pools as the season progresses. But sometimes I like to pretend that we're lost. Sometimes the group doesn't like that...just kidding!

If you would like to read more about Shackleton and Antarctica, check out Endurance: Shackleton's Incredible Voyage by Alfred Lansing. Amazing read and an incredible example of leadership.