The Observation Tube

One of the most unique activities available at McMurdo station is the Observation Tube, also known as the “Ob” Tube. This tube, which is like a big pipe, extends down through the sea ice with an observation chamber at the bottom so that visitors can sit below the sea ice and experience the marine environment. The bright turquoise lid that marks the opening to the Ob Tube sits only about a foot off the sea ice; it would be easy to walk by without noticing it was there! It is just off the edge of Ross Island, where McMurdo station was founded, so you can walk from the station to the tube. The sea ice is about 9 feet (2 meters) thick and below it is 75 feet (23 meters) of water. The tube itself is about 20 feet long and 3 feet wide, so only one person at a time can climb down and peek beneath the ice. If you’re at all claustrophobic, like me, this seems like a daunting task. Add 20 pounds of extreme weather gear and large bunny boots, and you start to question whether it’s safe at all! We all swallowed our fears, however, as the science nerds in us took over. The marine environment supports most of the wildlife on this extreme continent, and we couldn’t pass up a chance to see below the sea ice in this otherwise desert landscape!


Climbing down the tube was both a bit nerve-wracking and exciting. It was so narrow I had to lean my back against the wall to have just enough room to bend my knees and take the next step down. In bunny boots it took a minute to get to the bottom. Looking up, the rest of the team closed the lid on top of the tube, plunging me into the darkness beneath the ice. After a couple of minutes, my eyes adjusted and I realized there was a lot of light below the ice! The sun penetrated even 9 feet of ice and the water was a dark blue. There were windows all around, so I could see in every direction. There were even ice crystals forming around some of the window edges. Thousands of tiny larval fish were swimming all around, and a large transparent jellyfish drifted slowly by. Below the tube, I could make out a diver, another scientist exploring the sea life on the ocean floor. Looking up at the ice above, I saw that the ice was brown underneath because a layer of algae was growing!


The most exhilarating thing was the Weddell seal. Bright and clear, as if it was right below me, the trills and chugs of a Weddell seal were unmistakable. The vocalizations were so strong I could feel the vibrations through the walls of the tube. A reminder of how well sound travels in water, I never saw the seal; I could only listen.

I could have stayed in that tube for hours, just watching the world around me. But Emma was too hungry, so we went to dinner instead… We all hope to go back before we leave, and maybe we’ll get a glimpse of that Weddell seal underwater!

Written by: Sophie Whoriskey

Heather Liwanag