Antarctic voyage

“Our square sails are braced right now for the changing wind that we expect ahead as we cross Drake Passage, between Cape Horn and Antarctica,” says Mike Stewart, the boatswain of the Dutch tall ship Europa. Surging along the crests of 20-foot, slate-gray waves, the Europa is taking 15 crew members and 40 sail trainees to the Antarctic Peninsula.

The wind moans in the rigging, setting every brass hook and teak panel clanking, rattling, shivering, and heaving. Regularly thrown off balance, the men and women on board are willing to put up with discomfort to see the effects of climate change in Antarctica firsthand.

The impending collapse of the 5,600-square-mile Wilkins Ice Shelf adds a sense of urgency to the voyage. The Antarctic Peninsula, which stretches 750 miles north from the continent into Drake Passage, is arguably undergoing the fastest rate of climate change of any region on earth.

As the Europa approached Antarc­tica in late January, snow fell frequently, forming sodden clumps and then melting. Gentoo penguins leapt in the sea like miniature porpoises.

Antarctica is breathtaking. It’s a frozen desert with almost no precipitation. Along its coasts are the breeding grounds of humpback whales, seals, and penguins.

Statistically, the polar continent is just as breathtaking. Having 1-1/2 times the surface area of the United States, Antarctica contains 7 million cubic miles of ice, which has an average thickness of 1.6 miles.

Virtually an icemaking machine that has locked up 70 percent of the planet’s freshwater, Antarctica is undergoing rapid change.

According to one estimate, 550 cubic miles of Antarctic ice are calved into the sea each year, while about 407 cubic miles of compacted snow are added each year. The net loss seems slow, but the results along the water’s edge can be dramatic.

As the Europa arrives at Trinity Island in the Palmer Archipelago, humpbacks blow in the distance, and leopard, fur, and Weddell seals bask on rocks. Sharply angled pinnacle icebergs of every description loom: giant “cathedrals” of opaque bluish crystal; flat islands of ice shaped like aircraft carriers; one looks like a swallow perched on a mount.

But also evident are signs of the “great melt.”

“The breakup of several Antarctic ice shelves since the beginning of the 1970s is an important indicator of climate change in the Antarctic Peninsula,” says Ken Jezek, a geophysicist at The Ohio State University’s Byrd Polar Research Center in Columbus and a world authority on polar ice. “Removal of these ice shelves has eliminated an important restraining effect. So glaciers on the rocky interior of the peninsula are now more rapidly pumping ice into the ocean.”

Dr. Jezek is scientific lead of the Global Inter-agency International Polar Year Snapshot Year (GIIPSY), which is using earth observation satellites from several countries to measure ice thickness and ice velocity at the poles. “The basic force of gravity presses down on the ice sheet, causing it to spread,” he says. “But shear at the base and along the sides resists that spreading. The interplay between these stresses determines the motion of the ice sheet. Estimating how that interplay might change in the future could well enable us to predict the behavior of the ice sheet.”

One of the best tools for measuring the thickness and movement of ice is Radarsat-2, a satellite operated by a Canadian aerospace company. In 1997, Jezek and his team at the Byrd Center developed the first mosaic map of Antarctica using data from the first-generation Radarsat-1. They have completed other maps since. This type of mosaic provides a tremendous amount of detail, since radar penetrates cloud cover, fog, and the polar night.

Last month, Radarsat-2 completed a new mapping mission of Antarctica, and the Canadian Space Agency is planning to process the data and develop new maps, establishing comparative data sets 12 years apart.

Robert Saint-Jean, manager of radar data in the Satellite Operations Directorate of the Cana­dian Space Agency, says Radarsat-2 can image down to three feet. “One of the main technical advantages of Radarsat-2 is the ability to slew – to turn and look at the left side of its track. Usually synthetic aperture radar systems look to the right side. This enables us to observe the central part of the Antarctic continent on a day-to-day basis, mapping the interior of the continent for the very first time.”

Mr. Jezek and the Canadian Space Agency are spearheading efforts to coordinate the imaging activities of Earth observation satellites in the US, Europe, and Asia, so that each “bird” images a distinct Antarctic region, avoiding duplication.

From one bay to the next, the Europa drops anchor in front of enormous glaciers plunging down to the sea at very high angles. “You have all of these pull-apart crevasses,” says Mr. Stewart, the boatswain, who trained as a geologist, “all of them parallel to the shore, parallel to the toe of the glacier, and these will just fall away all at once, like bookshelves in a library dropping down. It sounds like rifle shots.”

According to Europa’s captain, Klaas Gaastra, a giant iceberg calving off a glacier last year set off a 15-foot impact wave that could have overturned the ship. Fortunately, there was just enough time to let out all the anchor cable.

Evgeniyy Karyagin is the base commander at Ukraine’s Vernadsky station, on the west side of the Antarctic Peninsula. Formerly known as Faraday Station, the base was transferred from Britain to Ukraine in 1996. Researchers here focus on atmospheric and climate research.

Mr. Karyagin brings his experience as a seismologist for the Ukrainian National Space Agency to study what he calls “ice quakes” – nontectonic seismic events caused by the glacier movements.

“I receive signals from the iceberg-generation process,” he says. “The whole coast of the Antarctic Peninsula has many glaciers, each of which drops a big weight of ice into the water, generating a very small signal like an earthquake. Every day, I receive about 1,000 to 2,000 such signals. If I count the number of signals I receive from glaciers, I can measure the total weight of freshwater reaching the ocean in the form of ice.”

Rick Atkinson, manager of Port Lockroy – once a British scientific base but now a heritage site welcoming 15,000 cruise-ship tourists each summer – says that his area has seen warmer temperatures recently. “This last winter, our automatic weather recorders here told us that the coldest temperature all winter was only 6 degrees F., and most of the time it was just around freezing, or just below.”

As the Europa nudges into smaller pieces of ice, they make a crackling sound as air bubbles trapped inside are released by the sun and water.

“Is the breakup of Antarctic ice shelves a cause for concern?” Jezek asks. “Expressed in that way, I find [that] people become unduly worried.... I prefer to think of it as an observation that should be considered and planned against. Sea level will surely continue to rise, and this will have an impact on coastal communities. What we need to do now is better refine our estimates of the rate of that change so that people can intelligently plan.... I think people in general will be more receptive to that message instead of some of the gloom and doom you often see reported.”