An international research team has discovered that tropical areas and the north temperate zone experienced different transitions during the last deglaciation that followed an abrupt climate change event 12,000 years ago.
The team, headed by National Taiwan University geology professor Shen Chuan-chou (沈川洲) and University of Texas geophysics professor Judson Partin, said it found that the time required to reach and recover from full glacial-like conditions — in terms of temperature and precipitation — in the North Pacific clearly differed from that in the Atlantic during the Younger Dryas, which was an abrupt return to glacial-like conditions during the transition to a warmer interglacial climate that occurred at the end of the Late Glacial interval
The team analyzed a stalagmite, which was formed between 11,000 and 13,000 years ago on the Philippine island of Palawan, using uranium-thorium dating to reconstruct the hydroclimate history of the area at the time.
The researchers determined that the onset and termination of the Younger Dryas interval was synchronous across the globe, starting from 12,800 years ago and ending 11,600 years ago, Shen said.
However, the tropical hydroclimate changes were more gradual — spanning more than 100 years — than the abrupt temperature changes seen in the northern Atlantic Ocean, which occurred within a period of 10 to 100 years, he said.
Analyzing Greenland ice core records, the team found that temperatures in the North Atlantic dropped 5oC to 10oC within two to three years during the Younger Dryas, which gives credibility to the depiction in disaster film The Day After Tomorrow of extreme weather events ushering in a global cooling and new ice age, Shen said.
However, it took about 400 years for temperatures to drop 1oC and for the annual precipitation to drop from 2,000 millimeters (mm) to 1,500mm on Palawan, he said.
When the Younger Dryas was over, it took from several years to 100 years for the north Atlantic regions to recover to a warm and humid climate, but it took 440 years for Palawan to return its previous climate, with an annual precipitation of 2,500mm, he said.
Record-breaking high temperatures in various places around the globe in recent summers, combined with northern hemisphere winters becoming extremely cold, might be a sign of another global cooling event, he said.
If such an event happens, the climate in southern Taiwan would gradually turn dry and cold, while the north would experience colder, but more humid winters because of the strengthened northeastern monsoon.
The team’s study was published last week in the US journal Nature Communications.
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