Excerpted with permission from Lost Antarctica: Adventures in a Disappearing Land, by James McClintock. Available from Palgrave Macmillan. Copyright © 2014.
No voyage from South America across the Drake Passage to Antarctica is complete without celebrating the first sighting of an iceberg. Usually one can expect to see one about two-thirds of the way across the Passage. On Antarctic cruise ships, a bottle of fine champagne is awarded to the first guest to inform the officer on the bridge of the sighting. Aboard research vessels, scientists are outwardly subdued, as if sighting the first iceberg is routine and benign. But scientists hide their excitement behind their professional demeanor. Icebergs are irrefutably stunning—transcending both science and art. When sunlit on a clear day, they are so brilliantly white they are impossible to look at without squinting. Where snow has melted or blown free, a translucent-light to deep-azure blue emerges from the ice. At the water line and up to twenty or so feet below the sea’s surface, the shades of turquoise and lime green can take an onlooker’s breath away. As icebergs melt and shrink, they periodically tip over, exposing their underbellies of glassy-smooth or pockmarked surfaces. As a precaution against sudden rollovers, our vessels give icebergs a wide berth, and the National Science Foundation (NSF) Antarctic dive program prohibits scuba diving in their proximity. But one need not enter the water to enjoy such surreal beauty. One of my favorite places in Antarctica to take nature photographs is from a small boat slowly winding its way through gardens of icebergs. As if sculpted by an artist, their myriad shapes—some reminiscent of animals, castles, or treasures from the world’s finest modern art collections—provide a virtual smorgasbord of photographic potential.
Icebergs are large pieces of floating freshwater ice, generally projecting from just a few to around two hundred fifty feet above sea level, and weighing hundreds to millions and occasionally even billions of tons. They can originate from a variety of sources, such as being shed from a snow-formed glacier (known as a calving event), or from cracking off an ice sheet. The word iceberg itself is derived from the Dutch [ijsberg] meaning “ice mountain.” This term is somewhat ironic considering that 80 to 90 percent of an iceberg is hidden below the surface of the water. If upside down, however, an iceberg would truly be an ice mountain.
Antarctica boasts some of the largest icebergs ever recorded. In 2000, Iceberg B-15 broke free from the Ross Ice Shelf—a floating platform of ice that can be hundreds or even several thousands of feet thick. (Large icebergs are given designations so they can be tracked.) The Ross Ice Shelf is the largest ice shelf in Antarctica and is about the size of France. Remarkably, a vertical ice wall towering 50 to 100 vertical feet fronts 370 miles of the Ross Sea. The ice shelf was named for Captain James Ross Clark who first sighted the shelf on January 28, 1841. Iceberg B-15 measured twenty-two miles wide and 183 miles long, and was estimated to weigh three billion tons. At 4,200 square miles, the iceberg was eight times the size of the city of Los Angeles. I was fortunate to witness one of these behemoths on a cruise to Antarctica aboard the Explorer II—on whichI was lecturing with a friend, geologist Henry Pollack—in 2007. We sailed for hours, seemingly within reach, of a thirty-one-mile-long iceberg that had grounded itself near Clarence Island off the northern tip of the Antarctic Peninsula. Henry, who had visited Antarctica frequently over a span of eighteen years, was, like me, nonetheless awestruck by this iceberg’s grandeur. Emerging one hundred vertical feet from the sea, the immense iceberg towered above us, dwarfing our ship as we passed.
As global temperatures rise, icebergs will more often break off, or calve from, the mainland. Throughout the decade I have worked at Palmer Station, I have witnessed many bergs calve from their glaciers. About once a week, I would be startled by a loud, thundering crash. Leaping from my desk on the second floor of the Palmer BioLab, I would join others running down the hall to throw open the door and watch the waves rolling up neighboring Hero Inlet—waves brought on by a house-sized chunk of the Marr Glacier breaking free and plummeting into the sea. Now when I visit Palmer Station, the calving events have become so routine that my colleagues and I in the BioLab don’t even bother to move from our desks when we hear the glacier roar. Sometimes, three or four calvings happen in a single day. Indeed, those who have worked at Palmer Station over the past decade don’t need to consult journals, television programs, or the Internet to understand how the climate is changing. Furthermore, as the geography changes, so do the names of actual locations. When the receding ice tongue of the Marr Glacier recently revealed an island rather than a seemingly long-established point of land, Amsler Island was officially born.
The frequency of icebergs calving off glaciers and ice sheets breaking up will inevitably increase as waters along the Antarctic Peninsula and other regions of western Antarctica continue to warm. Larger icebergs will also become more common as they are shed from ice sheet break-ups, and their increased mass will permit them to drift farther north before finally melting. They will also begin to show up in odd places. On November 16, 2006, while I was on sabbatical at the University of Otago in the city of Dunedin on the southern island of New Zealand, government officials spotted a large iceberg off the coast—the first iceberg sighted from a New Zealand shoreline in seventy-five years. It turned out to be one of a flotilla of over a hundred icebergs. Immediately, the media was abuzz with news about the impacts of climate change, and the New Zealand icebergs soon became a major tourist attraction. Tourists paid $300 apiece for a helicopter ride over the fields of ice, and for a bit more cash, they could land on the large berg within sight of Dunedin. A tour company quickly organized an iceberg wedding, but had to scuttle it when the helicopter pilot decided it was unsafe to land.
A warming Antarctic Peninsula riddled with icebergs has consequences that are hidden from the casual observer. The increased amount and sizes of icebergs scouring the coastal seafloor disrupt the marine communities there. Marine biologists have long known that near-grounded icebergs behave much like earth movers at construction sites, displacing tens of thousands of square yards of seafloor sediment. The exposed portion of an iceberg acts as a sail, transferring the energy of wind and current to motion, causing the berg’s base to plow through soft sediments and scrape over hard rocky bottoms. Massive iceberg scars extend for miles along coastal Antarctic seafloors, and these are devoid of seaweed, sponges, sea anemones, soft corals, sea spiders, starfish, brittle stars, and even fish. Over a period of a few years, the process ecologists refer to as community succession will kick into gear along these iceberg scars. Temporary communities of rapidly settling and fast-growing, but short-lived, seaweeds, sponges and sea squirts will give way to more stable “climax” communities comprised of more competitive seaweeds and marine invertebrates that grow slower and have longer life spans. Climax communities are ecological communities in which populations of bacteria, plants, and animals remain stable and exist in balance with each other and their environment. In the big picture, Antarctic seafloors that are subject to intermediate levels of periodic iceberg scour are checkered with short-term opportunistic and long-term stable communities and, as such, sustain higher overall diversities of species. But just as intermediate levels of iceberg disturbance may increase species diversity, too much iceberg disturbance may actually compromise this diversity. Heavily ice-scoured seafloors, like a graded construction site, can be biological deserts. Climate warming could result in an overabundance of coastal icebergs that regionally decimate near-shore seafloor communities.
Icebergs can also have unforeseen impacts on Antarctic marine birds. Following the 2005 break-up of B-15, a massive offspring (renamed B-15A) grounded at the mouth of McMurdo Sound. Its position effectively blocked the outflow of pack-ice from the Sound while simultaneously cutting off the Adélie and emperor penguins from their food resources. This blockage diverted the penguins to a route that effectively doubled the distance they would normally travel, from about 60 to 120 miles. Until the massive B-15A iceberg floated free several years later, biologists routinely found emaciated penguin carcasses en route between rookery and sea.
The physical attributes of the Antarctic Peninsula—its icebergs, annual sea ice, ice shelves, glaciers, winds, and currents—are important players in a rapidly warming environment. Some are increasing in size and abundance (icebergs), some are diminishing in duration, size, or extent (annual sea ice, ice shelves, and glaciers), and others (winds and currents) are subject to regional variation. All are subject to change. When considered collectively, they portray a dynamic ecosystem undergoing remarkable transition in a relatively short period of time. These incredible changes affect the myriad of Antarctic marine organisms that over the millennia have adapted to survive in one of the world’s most stable locations. Some of these organisms may adapt, but the vast majority of species here have become so finely tuned to their surroundings that they don’t have much wiggle room.