Imagine yourself, suspended weightless, flying beneath deep blue clouds of ice frozen for centuries, above fields of grey stone punctuated with pink and white anemones, sea urchins, and other creatures. This is an ice dive beneath the largest ice shelf in the world; spanning roughly 182,000 square miles, and about the size of Spain, it is bordered by the Ross Sea, with the King Edward VII Peninsula to the east and the Transantarctic mountains to the south. While its interior extends for a distance of 400 to 600 miles, it is 500 miles long. The shelf’s vertical cliff face rises up from between 50 and 200 feet above the surface, which makes it easy to understand why Captain James Clark Ross, who discovered it, named it the Great Ice Barrier. Nearby McMurdo Sound serves as a resupply route for aircraft and cargo vessels, plus it is a base for scientific research. Let’s take a closer look.
Life Beneath the Ice
Due to the amount of ice cover and the often extreme weather conditions, there is a limited amount of life beneath the ice in the areas where it is thickest, but in areas where ice coverage is mostly seasonal, there are greater concentrations of life; this is directly related to the amount of sunlight organisms receive, particularly the algal life forms upon which so many others rely for survival. The seasonal production cycle in the Ross Sea is inextricably linked with fall ice formation, along with spring and the summer thaw.
There are approximately 100 species of phytoplankton which provide a base for the marine food chain; south of the Antarctic convergence, there are approximately 200 species of finfish, 25 percent of which are endemic to the area. Krill feed penguins, squid, fish, seabirds, and even whales; all of which have developed low metabolic rates which allow them to survive under frigid Antarctic conditions while maintaining a high rate of protein synthesis. Despite its remote location, the area is of such scientific significance that it is the site of an international laboratory where weather, climate, glaciology, oceanography, and glaciology studies take place.
Diving Under Antarctic Ice
Ice dives typically take place beneath specially constructed ice houses, where permanent holes have been cut through the ice, which is two meters thick. To make your way beneath the ice, you dive down through a tube drilled with an enormous auger mounted on the back of a tracked vehicle. New holes are drilled at different dive sites, and at each site, a secondary hole, capped with an ice-covered foam and plywood lid and marked with a flagpole, provides divers with an alternate route to the surface in the event the primary route is blocked by a Weddell Seal. As divers breathe underwater, their bubbles dislodge platelet ice, sending it to the surface of the entry holes, where it is removed with a dip net to keep the route clear.
At some sites, seal made holes are used instead of manmade holes; these are the result of Weddell Seals expanding cracks in the sea ice. The seals keep their holes open year-round and as they are much more docile than the elephant and leopard seals found in other Antarctic locations, they don’t mind sharing their holes with divers.
It’s easy to see these holes while underwater, even from a distance, as shafts of light penetrate, making their way down through the deep velvety blue colored water in much the same way as light sometimes penetrates a cave ceiling.
Beneath the surface, you’ll see Weddell Seals, huge sea stars in shades of pink and yellow, and even some massive sea worms which are capable of growing to be about two meters long. Most dive sites here are set up specifically with scientific research in mind; while you will see some incredible things, a big part of the overall experience is interacting with the scientists and learning more about their research.
Diving in Antarctica tends to take place during the summer months, when the sun never sets; during the polar winter, when darkness reigns, very few teams stay onsite, and recreational diving is almost unheard of since weather conditions are simply too unpredictable to ensure anyone’s safety. The temperature beneath the ice is 28 degrees, and layers of clothing are a must. You’ll need your own redundant equipment plus a drysuit; your tour company will generally provide you with an entire list of items that should be brought along for the journey. An area where few dare to venture, this is one place you’ll always remember.