The last fatalities at sea near the continent were in February 2011, when a Norwegian-flagged, steel-hulled yacht with three crew vanished during wild weather in the Ross Sea.
It's not only tourists who get into trouble. Searchers will wait until at least October to recover the bodies of three Canadians involved in scientific research who died in a plane crash in January near a summit in the Queen Alexandra range. A fire aboard a Japanese whaling ship in the Ross Sea killed a crew member in 2007. And anti-whaling activists lost a boat that collided with a whaler in 2010. No one was injured.
Hemmings said tourist ships have been involved in several mishaps in Antarctica in the past five years.
"Misadventure can befall anybody," he said, but he added that the number of tourist ships coming to Antarctica's busiest areas was a concern.
While Antarctica is as big as the United States and Mexico combined, tourists and scientists for the most part keep to areas that aren't permanently frozen and where wildlife can be found. Those account for less than 2 percent of the continent.
It's a land of many hazards, not all of them obvious. The dry air makes static electricity a constant threat to electronics and a fire risk when refueling vehicles. Residents quickly get into the habit of touching metal fixtures as they pass, and metal discharge plates are set beside all telephones and computer keyboards.
Most tourists arrive on the Antarctic Peninsula, which is easily accessible from Argentina and Chile. The next most popular destination is the Ross Sea on the opposite side of the continent, a 10-day sail from New Zealand or Australia.
Both landscapes are intensely bright and profoundly silent during the 17 weeks between sunrise and sunset in the summer. The peninsula is a milder environment and has a wider variety of fauna and flora.
The Ross Sea, where the Royal Society Range soars 4,200 meters (13,200 feet) above the ice-clogged waters of McMurdo Sound, demonstrates the colossal grandeur for which Antarctica is renowned. It was also the starting point of British expeditions to the South Pole during the so-called heroic era of Antarctic exploration from 1895 to 1915. The early explorers' wooden huts still dot the coast.
The Ross Ice Shelf, the world's largest mass of floating ice covering an area almost as big as Spain, rises as steep, gleaming cliffs 60 meters (200 feet) from the sea.
Two cruise ships visited the sea's Ross Island, connected to the continent by ice, last summer. Summer temperatures average minus 6 degrees Celsius (21 Fahrenheit) but often seem colder due to wind chill.
Passengers visited the largest settlement in Antarctica, the sprawling U.S. McMurdo Station, which can accommodate more than 1,200 people, as well as New Zealand's neighboring Scott Base, which sleeps fewer than 90. Many also visited a drafty hut built by doomed British explorer Capt. Robert Falcon Scott in 1902 as an expedition base a few hundred meters (yards) from McMurdo Station.
The two bases, separated by a 3-kilometer (2-mile) ice road, don't facilitate tourism, but tourists are generally welcomed. Both have well-stocked gift shops.
Antarctic New Zealand's environment manager Neil Gilbert said more robust monitoring is needed to track impacts of tourism.
"The Antarctic Peninsula ... is one of if not the most rapidly warming part of the globe," Gilbert said. "We really don't know what additional impact that those tourism numbers ... are having on what is already a very significantly changing environment."
There are fears that habitat will be trampled, that tourists will introduce exotic species or microbes or will transfer native flora and fauna to parts of the continent where they never before existed.
A major fear is that a large cruise ship carrying thousands of passengers will run into trouble in these ice-clogged, storm-prone and poorly charted waters, creating an environmentally disastrous oil spill and a humanitarian crisis for the sparsely resourced Antarctic research stations and distant nations to respond to.
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