Tag Archives: Antarctic

Humpback whale

Record number of whales in Antarctic Bay

Scientists have observed a “super-aggregation” of more than 300 humpback whales gorging on the largest swarm of Antarctic krill seen in more than 20 years in bays along the Western Antarctic Peninsula.

The sightings, made in waters still largely ice-free deep into austral autumn, suggest the previously little-studied bays are important late-season foraging grounds for the endangered whales. But they also highlight how rapid climate change is affecting the region.

“Such an incredibly dense aggregation of whales and krill has never been seen before in this area at this time of year,” says Douglas P. Nowacek, Repass-Rodgers University Associate Professor of Conservation Technology at Duke. Most studies have focused on whale foraging habitats located in waters farther offshore in austral summer.

Nowacek and his colleagues observed 306 humpback whales – or about 5.1 whales per square kilometer, the highest density ever recorded. They measured the krill biomass at about 2 million tons. Small, floating fragments of brash ice covered less than 10 percent of the bay.

Advancing winter sea ice used to cover much of the peninsula’s bays and fjords by May, protecting krill and forcing humpback whales to migrate elsewhere to find food, Nowacek says, but rapid climate change in the area over the last 50 years has significantly reduced the extent, and delayed the annual arrival, of the ice cover.

“The lack of sea ice is good news for the whales in the short term, providing them with all-you-can-eat feasts as the krill migrate vertically toward the bay’s surface each night. But it is bad news in the long term for both species, and for everything else in the Southern Ocean that depends on krill,” says Ari S. Friedlaender, co-principal investigator on the project and research scientist at Duke.

Antarctic krill are shrimplike creatures that feed primarily on phytoplankton and live in large swarms in the Southern Ocean. Penguins, seals, seabirds and many whale species rely on the protein-rich, pinky-sized crustaceans as a source of food. Commercial fisheries are allowed to harvest up to three-and-a-half tons of the krill a year as food for farm-raised salmon and for oil, rich in omega-3 acids, which is used in human dietary supplements.

Around the Western Antarctic Peninsula, krill migrate in austral autumn from open ocean waters to phytoplankton-rich bays and fjords, where juveniles feed and the population overwinters under the protective cover of ice. There is a strong correlation between the amount of sea ice and the amount of krill that survive the long, harsh Antarctic winter.

Further Reading:
Duke University Marine Laboratory

antarctic

Scientists Call for More Antarctic Ocean-Observing

Oceanographers are calling for more ocean-observing in the Antarctic, particularly in the Western Antarctic Peninsula, or WAP.

This mountainous arm of the continent stretches north toward South America.

In a paper published in Science, the authors argue that research in this region is imperative: The WAP’s climate, they say, is changing faster than the climate in the rest of the continent, while Antarctica’s climate is changing faster than anywhere else on the planet.

The scientists observe that 87 percent of the peninsula’s glaciers are in retreat, the ice season has shortened by 90 days, and perennial sea ice is no longer a feature of this environment. They also point out that these changes are accelerating.

Until recently, most oceanographic research in the Antarctic was done from government-funded ships. Ships are expensive, limited by harsh weather, and only useful during the Antarctic summer. Scientists also have been using satellite data for the past 30 years, but since the Antarctic is often cloud-covered, such data are often incomplete.

Climate change will alter marine ecosystems; however, the complexity of the food webs, combined with chronic undersampling, constrains efforts to predict their future and to protect marine resources. Sustained observations at the West Antarctic Peninsula show that in this region, rapid environmental change has coincided with shifts in the food web, from its base up to top-level predators. New strategies are needed to gain further insight into how the marine climate system has influenced such changes and how it will do so in the future. Oscar Schofield of Rutgers University, and his colleagues, suggest robotic networks, satellites, ships and instruments mounted on animals and ice should collect data needed to improve numerical models that can then be used to study the future of polar ecosystems as climate change progresses.

Further Reading:
How Do Polar Marine Ecosystems Respond to Rapid Climate Change? Schofield et al. Science 18 June 2010: Vol. 328. no. 5985, pp. 1520 – 1523 pp. 1520 – 1523
Rutgers: The State University of New Jersey