Prof. Maureen Raymo, earth sciences, Boston University discussed the origins of ice ages on Earth in a packed classroom in Snee Hall yesterday afternoon.
Raymo explained that by measuring the amount of two particular isotopes of oxygen – oxygen-16 and oxygen-18 – in the water at the bottom of the ocean, geologists are able to determine how much ice at one point covered the surface of the planet.
She cited in her lecture the “Orbital Hypothesis,” first proposed by Serbian geophysicist Milutin Milankovitch in 1920, which attributes the coming and going of ice ages to the “precession,” or wobbling of the Earth on its axis. According to Raymo, variation in precession is responsible for “amplifying or mutating seasonal changes in each hemisphere.”
Raymo also described what she called “the hundred-thousand year problem,” an unexplained discrepancy between the oxygen data and expected models for ice growth.
“[It’s] the greatest problem … waiting to be solved.” said Raymo. “Something’s going on within the climate system [to explain this].”
Raymo proposed to the audience that the annual give-and-take between melting and accumulation in the northern and southern hemispheres has transitioned to a sole “give” from the north being resisted by the Antarctic ice sheet.
“Antarctica is [now] being controlled by the northern hemisphere.” said Raymo. “There’s grass growing [in West Antarctica].”
The audience was composed of a good mix of Cornell students and Ithaca residents. Several seniors from Ithaca High School were in attendance as well. Colin Stuart, one of the high schoolers, explained that they were there to fulfill a community outreach requirement for their Advanced Placement Environmental Science class.
“One of the options [to meet the requirement] was to come to this lecture,” said Sam Paskin-Flerlaye, another student. “We’re excited to be here.” he said.
Raymo, who is also an adjunct scientist at the Woods Hole Oceanographic Institute in Woods Hole, Mass., lectured as a Snee Graduate Organization invited speaker. Her lecture was part of the Department of Earth and Atmospheric Sciences fall 2005 lecture series. She is also lecturing today at 11:30 a.m. in 401 Hollister Hall about “North Atlantic deep water circulation changes over the Pleistocene.”
Archived article by Chris Barnes