The Polar regions of the Arctic and the Antarctic are both cold. Beyond that, you can’t really talk about conditions at one pole based on the conditions at the other. Case in point: Sea ice. Since 1979, there’s been a significant decrease in Arctic sea ice—about 4% per decade—correlated closely to an increase in global average temperatures.
But Antarctica is different. Averaged out, sea ice around the Frozen Continent has grown by a little less than 1% per decade. From place-to-place, season-to-season, and year-to-year, however, the trends in Antarctic sea ice have shown a lot more variability than those in the Arctic. In other words, there’s a lot we don’t know about sea ice in the Antarctic and, right now, the data we have is too noisy to say much about it for sure. At least, in a big picture sort of way.
In the small picture, though, this year has been tough one on the Ross Sea, near the McMurdo scientific research station. The sea ice in McMurdo Sound is thin; the snow is thick, and both those things have big implications for the scientists who normally work out on the sea ice. Henry Kaiser is a diver, filmmaker, and musician who has spent the last 10 years aiding scientists on research dives off the Antarctic coast. In this story, he talks about how thinner-than-normal sea ice affects scientists’ ability to do their jobs.
Research Diving in Antarctica
My ninth season down here at McMurdo Station, Antarctica has been a season like no other. It's always been an easy thing, in seasons past, to travel where our work might take us, over the frozen surface of the Ross Sea. Seal scientists, fish scientists, and many others are used to scurrying about via snowmobiles and larger tracked vehicles across the frozen ocean. But this year, as a result of much thinner ice, thicker snow cover that prevents ice formation, and higher ambient temperatures, we are suddenly faced with a giant Triangle of Inaccessibility. The Triangle threatened to hinder our work or prevent it altogether. Take a look at that big red isosceles triangle on the map, it's about 7 x 7 x 11 miles in size and it's where most of the scientists on the local sea ice usually conduct their work.
Let's zoom out on that last map and look at the Western side of Ross Island, just downslope from the massive and active Erebus Volcano. This map is what we were shown at the beginning of the season. That big red area was a forbidden zone to vehicle traffic. Some scientists could request helicopter time to get out to their field sites; but it looked nearly impossible to set up the normal field camps and commute back and forth to "town.”
The friends and colleagues here who work on the ice have pulled hard together in the past month. They have found ways to get into the triangle by snowmobile and Pisten Bully—a snow-grooming vehicle like the kind used to maintain ski trails. A plywood bridge is being constructed over the Tent-EGT crack; that will prevent our vehicles from being swallowed up by the sea.
Cracks have formed in the thin ice and daily measurements of the cracks that need to be traversed are taken, as those cracks could become impassible at anytime. Nobody wants to quickly sink to the bottom of the Ross Sea in the frozen coffin of $100,000 tracked vehicle. Take a look at the situation map in the hall of the Crary lab here:
Folks add to this sea ice hackers' map every day and we all stay in touch with each other, trying to figure new ways to get our work accomplished. Some areas are still inaccessible and larger vehicles like those that we use to drill dive holes will never be able to enter the Triangle this season. In order to grab some special sea urchins for my boss, Gretchen Hofmann, we had to take a helicopter out to Cape Evans, about 20 miles north, and use a "hotsie" hole melter (made here from a converted carpet cleaning machine) to melt our dive hole. In the process, bad weather got us stuck there overnight and we got to camp out next to Robert Scott's historic hut. This week, I'll head out to Cape Royds, 30 miles from station, by helicopter with the penguin researchers, who don't have any way to drive to the Adelie penguin colony they’re studying.
Looking back over the past years to 2005, we can see that the sea ice edge, the place where the frozen ocean turns to open water, has been getting closer and closer every year. Is climate change to blame? Nobody is sure.
One reason that the sea ice edge was farther out in the earlier years of this graphic, was due to the massive iceberg, B-15, that blocked McMurdo Sound for a few years. B-15 prevented the ice in the sound from breaking up and let much thicker ice develop there. This 20-foot-thick sea ice was quite resistant to being broken up by winter storms. As divers, we hoped each year that the ice in the Sound would break up and go out; hoping for easier dive-hole making and more light down below. At the end of the last Austral Summer that ice did finally go out. But it did not reform in the way that it always has in local institutional memory. Much heavier snowfall than is usual in this Antarctic desert covered the ice with an insulating blanket that prevented the low temperatures topside from forming thicker sea ice down below. Temperatures topside have been warmer, too.
Take a look at this chart.
I can tell you there is big environmental change here this season, as is evidenced by the Triangle. Being one of the folks here who gets to spend a good deal of time under that ice, in the 28° F waters of the Ross Sea, I can report that there is also a big change in visibility this year. Our normally 2000 foot visibility is reduced to 300 feet or 400 feet. The water seems almost milky or chalky, and visibility is worsening as the season continues in an accelerating manner.
Ice has been thin and snow-covered in many pre-B-15 seasons, without any change in visibility; so we know this odd and poor visibility is not a result of that. It is a change that has not been see before and we don’t even have a guess as to why it is occurring. The National Science Foundation likes to say that Antarctica is the canary in the coal mine for climate change—I hope that meme makes the point that changes like this demand our attention. I 've even noticed a few jellies and other creatures more associated with the open water appearing way back under the sea ice. They don't usually show up until the ice edge is much closer, a month or so from now. Yet another mystery of this very odd season.
Has a significant alteration in climate brought on these environmental changes? Will this be the new norm, and will scientists no longer have their fish hut camps out on the sea ice? Time and further research will tell. Something is going on here that has been a wake-up call for those of us who work on the ice this season. We will continue to react to a changing environment and try to figure out why it might be changing.
Finally, here's the most recent, official Sea Ice Map.
Published 10:00 am Thu, Nov 17, 2011
Antarctica, carousel, Science