The Ob Tube

Below the Ice

At temperatures below freezing, the water below the ice is crystal clear.  The sun shines through the ice above emanating colors of blue, green, yellow, and orange, accenting the deep blue of the watery world below.  A large jellyfish slowly pulses its path through the water.  The edge of Ross Island can be seen, dropping down to the depths; scattered along its underwater slope crawl bright red starfish and sea spiders.  White, flat, and shoe-lace-like, large worms creep along the sediment.  Shrimp-like critters (amphipod? decapod? copepod? I'm not a marine biologist!) swim placidly through the water column and along the underside of the ice.  Tiny, silver, antigregarious (I make words up sometimes) fish are spaced throughout the water column, moving would too if you were so cold!  *Interesting side note:  Antarctic fish have anti-freeze proteins they use to keep the water inside their cells and blood from freezing, since the temperature of the water is below the freezing point of their blood.

As terrestrial creatures studying Weddell seals, we are only able to observe the seals while they are on top of the ice or blowing bubbles in the holes in the ice.  But they're real home is the water, which is why all the pups are learning to swim.  They will spend most of their lives in the water after mommy leaves them.  One could put cameras under the ice at tide cracks or send a well-insulated diver down to watch and record the seals, or one could use an "Ob Tube" (or Observation Tube).  The Ob Tube is a vertical tube placed through the ice and into the water, just large enough for a man to crawl down to the bottom, where a very small space encircled with windows gives a 360 degree view of the world below the ice.  It is an enchanting experience for us who are always trying NOT to go below the ice (by falling in a crack or otherwise), but are always wondering..."what is it like down there?"

Hmmm...deep dark tunnel of delight
Looking back up the tube

Inside the Ob Tube--Glenn scanning for seals
Thierry hunting for penguins or seals out the windows

Tiny fish in the deep blue

Unfortunately, we are not permitted to have our own Ob Tube, but a visit to one right outside of McMurdo suffices for us, especially when we are treated to a real, underwater swimming seal (that is tagged!).  Sorry the video quality is so dark and poor, you might have to turn off all the lights and watch it at night to see anything:


  1. Eek, freaky clausties! Who was that swimmer?

  2. Wowie, LOVE the Ob Tube! Alas, only vicariously tho :-( ! I think this is one unique case where I would willingly climb down a deep, narrow, dark shaft like that to a tiny enclosed space. Where else but the ocean deep can you get the experience of being in another world without leaving this planet? Your photos are magnificent. Do you manage to get usable data from your Ob Tube visits? I could see just enough of the movie to be glad I watched.

  3. Don't know who the swimmer was, although it had some yellow tags! Probably a lone male, avoiding all the mayhem and fighting for females near the colonies.

    The Ob Tube was only visited twice, and only saw one seal swim each time, so no useful data. We have jokingly talked about asking for the Ob Tube for our field camp to start looking at mom and pup interaction behavior (how intensively is mom swimming with the pup, etc) to get an idea of maternal affects on the pups...which is something we really are looking at...

  4. Can we expect mayhem footage to come soon?


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