Of penguins' range and climate change.Variations in the range of Adelie penguins along one section of Antarctica's coast during the past 45,000 years are a keen indicator of climate change there, a new study suggests.
Adelie penguins thrive only at sites with ice-free terrain, an abundant marine-food supply, and access to open water during nesting season, which starts each October, says Steven D. Emslie, a paleontologist at the University of North Carolina North Carolina, state in the SE United States. It is bordered by the Atlantic Ocean (E), South Carolina and Georgia (S), Tennessee (W), and Virginia (N). Facts and Figures
Area, 52,586 sq mi (136,198 sq km). Pop. in Wilmington. To determine when such conditions occurred along the Ross Sea Ross Sea, arm of the Pacific Ocean, Antarctica, between Victoria Land and Marie Byrd Land. It was discovered in 1841 by Sir James Clark Ross, a British explorer. Ross Island with Mt. area of Antarctica, he and his colleagues carbon-dated Adelie bones, feathers feathers, outgrowths of the skin, constituting the plumage of birds. Feathers grow only along certain definite tracts (pterylae), which vary in different groups of birds. , and eggshells from 21 active and abandoned nesting sites in that region,
At a penguin rookery on Cape Hickey, a site near the present-day edge of the Ross ice shelf Ross Ice Shelf
World's largest body of floating ice. It lies at the head of the Ross Sea, which forms an enormous indentation in Antarctica. Its area is estimated to be about the size of France. , the scientists found samples dating back 27,000 to 43,000 years, a hint that during that period, as today, the Ross Sea was open water during the penguin-breeding season, says Emslie.
By contrast, a gap in the Adelie fossil record between 27,000 and 13,000 years ago at all sites along the Ross Sea that have been analyzed chronicles the northward north·ward
adv. & adj.
Toward, to, or in the north.
A northern direction, point, or region.
north advance of the Ross ice shelf during that period, Emslie and his colleagues argue in the January Geology.
Adelie penguins fully recolonized the Ross Sea coast only 8,000 years ago, after the most recent ice age ended, following the retreat of the ice shelf to near its present location. More-recent gaps in the fossil record at most sites in the area--one between 5,000 and 4,000 years ago, and another between 2,000 and 1,100 years ago--indicate periods when ocean conditions weren't favorable fa·vor·a·ble
1. Advantageous; helpful: favorable winds.
2. Encouraging; propitious: a favorable diagnosis.
3. for penguin breeding and the climate was substantially cooler than it is now, the researchers speculate.