Surprising pulses of ancient warming found in Antarctic ice samples
https://www.sciencemag.org/news/2020/08/surprising-pulses-ancient-warming-found-antarctic-ice-samples
Source: By Sid Perkins, Science Magazine. Excerpt: Earth’s ice ages are typically thought of as seemingly unending periods of bitter cold. But a new study suggests bursts of carbon dioxide (CO2) often entered the atmosphere during these times, providing decades or even centuries of relative warmth amid 10,000-year stretches of chill. Such pulses may have caused glaciers and ice sheets to retreat somewhat, thus opening up new areas for plants and animals. ... Nehrbass-Ahles’s team then analyzed portions of a 3.5-kilometer-long ice core drilled at one of the highest points in eastern Antarctica. Their samples capture times between 330,000 and 450,000 years ago—an interval that includes one complete ice age as well as the warm spells on either side. On average, each data point was separated from its neighbors by about 300 years, a four- to sixfold improvement in time resolution over previous studies. ...The team’s new analysis shows Earth’s climate “can change a lot faster than we’ve previously thought,” says Shaun Marcott, a paleoclimatologist at the University of Wisconsin, Madison, who wasn’t involved in the new study. The resulting shifts in ecosystems, although short-lived, could have been profound. Nehrbass-Ahles and his colleagues suggest the jumps in atmospheric CO2 result from changes in a conveyor belt of ocean currents in the Atlantic Ocean. When the Gulf Stream weakens, that warm current brings less heat to North Atlantic waters. Those changes in sea-surface temperature, in turn, cause weather patterns in the tropics to shift, triggering a shrinkage of wetlands, Nehrbass-Ahles says. The carbon-rich material stored in those formerly swampy zones then decomposes, sending a pulse of CO2 into the air to warm the climate. In modern times, these ancient pulses wouldn’t be impressive: A 10-part-per-million jump in CO2, which may have unfolded over 100 years or more in preindustrial times, could these days take only 4 or 5 years to transpire....
Source: By Sid Perkins, Science Magazine. Excerpt: Earth’s ice ages are typically thought of as seemingly unending periods of bitter cold. But a new study suggests bursts of carbon dioxide (CO2) often entered the atmosphere during these times, providing decades or even centuries of relative warmth amid 10,000-year stretches of chill. Such pulses may have caused glaciers and ice sheets to retreat somewhat, thus opening up new areas for plants and animals. ... Nehrbass-Ahles’s team then analyzed portions of a 3.5-kilometer-long ice core drilled at one of the highest points in eastern Antarctica. Their samples capture times between 330,000 and 450,000 years ago—an interval that includes one complete ice age as well as the warm spells on either side. On average, each data point was separated from its neighbors by about 300 years, a four- to sixfold improvement in time resolution over previous studies. ...The team’s new analysis shows Earth’s climate “can change a lot faster than we’ve previously thought,” says Shaun Marcott, a paleoclimatologist at the University of Wisconsin, Madison, who wasn’t involved in the new study. The resulting shifts in ecosystems, although short-lived, could have been profound. Nehrbass-Ahles and his colleagues suggest the jumps in atmospheric CO2 result from changes in a conveyor belt of ocean currents in the Atlantic Ocean. When the Gulf Stream weakens, that warm current brings less heat to North Atlantic waters. Those changes in sea-surface temperature, in turn, cause weather patterns in the tropics to shift, triggering a shrinkage of wetlands, Nehrbass-Ahles says. The carbon-rich material stored in those formerly swampy zones then decomposes, sending a pulse of CO2 into the air to warm the climate. In modern times, these ancient pulses wouldn’t be impressive: A 10-part-per-million jump in CO2, which may have unfolded over 100 years or more in preindustrial times, could these days take only 4 or 5 years to transpire....