Science journalist Jane Qiu is travelling to the Palmer ecological research station on the Antarctic Peninsula, joining researchers investigating how climate change has affected the region in recent decades. Please check back for her dispatches from the bottom of the world.
We have sailed well into the Drake Passage, a thousand kilometers of open water between Cape Horn in Chile and northern Antarctic. Gigantic waves pound the hull and flood the lower deck. A few giant petrels and albatrosses circle around us, gliding effortlessly and elegantly in the southern wind.
The Drake’s notorious gales are formed because of the perennial high-pressure system over the South Pole. That massive air mass flows eastwards – because of the Earth’s rotation – and circulates and accelerates clockwise around the continent with no land mass standing in its way. The unimpeded gales also produce the strongest and fastest ocean current on the planet – the Antarctic Circumpolar Current (ACC).
At the western shore of the Antarctic Peninsula, the ACC climbs up and onto the continental slope, supplying the coastal biota with warmth and nutrients from the deep. For reasons scientists do not yet understand, the current seems to be getting warmer, which, compounded with atmospheric warming, is changing the balance of the region’s ecosystem from phytoplankton algae to apex predators, says Joseph Warren, an ecologist at Stony Brook University in New York and principle investigator of the research cruise.
To build a comprehensive picture of such changes across the Southern Ocean, Warren and his colleagues will attempt to use sonar to determine what lives in those waters and where. After dropping a few of us off at the Palmer station at the western Antarctic Peninsula, the researchers will attach a tailor-made sonar system to the ship, shoot sound waves down into the ocean as the ship sails around the peninsula, and “listen” to what is bounced back.
“Animals are made of different materials and so reflect sound differently,” says Warren. “The amount of time it takes for the reflection to reach back to the ship also tells us which layer of the water column they live.” By homing in on particular echo signatures, the researchers hope to be able to monitor a large part of the food chain in the region over a long period of time.
The team are particularly interested in salps – jelly-like animals that have been increasing in numbers in parts of the Southern Ocean in recent decades. By contrast, the much more nutritious krill – shrimp-like creatures and a key food source of many animals in the Antarctic – are becoming less numerous. It’s important to know how widespread this shift in ecosystem composition is and what triggers such changes, says Warren.
Meanwhile, Melissa Rider and Steve Forrest of the Oceanites, a Washington DC-based not-for-profit organization that has been monitoring the population of seabirds at some 270 sites on the Antarctic Peninsula since 1994, will hop onshore in inflatable boats at various locations and count the number of nesting bird species, such as blue-eyed shags and penguins.
Although these surveys are far from comprehensive, the data show worrying signs of changes in some of the bird populations, especially penguins, on the peninsula, says Rider. On Petermann Island, part of the archipelago off the coast of the western Antarctic Peninsula, for instance, there are only about 400 breeding pairs of the Adélie penguin – compared to 1,000 when the French explorer and ornithologist Jean Baptiste Charcot did the first survey over a century ago.