On the horizon
Researchers have long observed "rivers of ice" flowing within large ice caps like Antarctica's. What accounts for faster-flowing rivers or streams of ice? According to a team of US scientists, a main driver is large lakes beneath glaciers.
Using satellite-borne radar, the team found four large, closely spaced under-ice lakes beneath East Antarctica's Recovery Glacier. Upstream of the lakes, where the slope is steep, the ice flows at a lethargic 6.5 to 10 feet a year. Below the lakes, where the slope is far more gentle, the stream zips along some 10 times faster. The newfound lakes cover a combined 5,135 square miles, nearly the area of Lake Vostok, the continent's largest lake. The stream adds 35 billion tons of ice to the ocean each year.
The researchers say the ice encounters less friction over the water. And when lake water freezes to the bottom of the glacier, it warms and softens it. The softer ice flows more easily. And the warmer temperatures prevent the ice from refreezing to the land downstream. The team, led by Robin Bell of the Lamont-Doherty Earth Observatory at Columbia University, also notes that these lakes can drain suddenly, scouring smooth channels that in effect further grease an ice stream's skids. Mapping more of these lakes and understanding their role will be important for forecasting changes in these streams. The results appear in Thursday's issue of the journal Nature.
The odd forms of marine life around deep-sea hydrothermal vents have intrigued scientists for decades. Now they have found direct molecular evidence for the tight relationship tiny bacteria have with their larger hosts there – in this case, a giant clam in the East Pacific known as Calyptogena magnifica.
"Giant" is relative. The clam measures only 10 inches across – a munchkin compared with the five-foot giant clams in the South Pacific and Indian Oceans. Still, it's big for its hostile, light-free environment. And it's a classic case of biological "I'll scratch your back; you scratch mine."
A team led by Harvard University's Irene Newton sequenced the genome of a microbe found in the clam's gut. They found that the microbe's genes encode for a range of compounds that allow it to "eat" the sulfur welling up from the undersea vents and convert it into a range of nutrients that clams and other vent inhabitants need to survive. The work appears in the current issue of the journal Science.
Birds may not exactly plan for retirement, but some species apparently plan for the future. That's the conclusion researchers at Cambridge University have reached after studying Western scrub-jays.
A team led by Nicola Clayton, with the university's department of experimental psychology, wondered if other animals can consciously plan ahead. Some look as though they do. But the urge to build a nest or hoard food usually is driven by instinct or immediate need, not in anticipation of future need.
The study? Eight birds each lived in their own three-compartment "condo." Before "breakfast," the team steered each bird to enter either a compartment with food, or one without food. The bird would remain there for two hours before being allowed to move freely for the rest of the day.
After three days of training to enable them to tell the feast compartment from the famine compartment, the birds were allowed to hoard food the night before. The jays consistently hid food in the famine compartment, anticipating that they might end up there the next morning. A similar test was run with a peanut and a kibble compartment to simulate a choice for breakfast. Jays cached significantly more peanuts than kibble in the kibble compartment, and vice versa.
The results, which appear in Thursday's issue of the journal Nature, suggest that the birds "have a sophisticated concept of past, present, and future, and factor this into their planning," Dr. Clayton concludes.