{"216771":{"#nid":"216771","#data":{"type":"news","title":"Borneo Stalagmites Provide New View of Abrupt Climate Events Over 100,000 Years","body":[{"value":"\u003Cp\u003EA new set of long-term climate records based on cave stalagmites collected from tropical Borneo shows that the western tropical Pacific responded very differently than other regions of the globe to abrupt climate change events. The 100,000-year climate record adds to data on past climate events, and may help scientists assess models designed to predict how the Earth\u2019s climate will respond in the future.\u003C\/p\u003E\u003Cp\u003EThe new record resulted from oxygen isotope analysis of more than 1,700 calcium carbonate samples taken from four stalagmites found in three different northern Borneo caves. The results suggest that climate feedbacks within the tropical regions may amplify and prolong abrupt climate change events that were first discovered in the North Atlantic.\u003C\/p\u003E\u003Cp\u003EThe results were published June 6 in Science Express, the electronic advance online publication of the journal \u003Cem\u003EScience\u003C\/em\u003E, and will appear later in an issue of printed publication. The research was supported by the National Science Foundation.\u003C\/p\u003E\u003Cp\u003EToday, relatively subtle changes in the tropical Pacific\u2019s ocean and atmosphere have profound effects on global climate. However, there are few records of past climate changes in this key region that have the length, resolution and age controls needed to reveal the area\u2019s response to abrupt climate change events.\u003C\/p\u003E\u003Cp\u003E\u201cThis is a new record from a very important area of the world,\u201d said \u003Ca href=\u0022http:\/\/www.eas.gatech.edu\/people\/Kim_Cobb\u0022\u003EKim Cobb\u003C\/a\u003E, an associate professor in the \u003Ca href=\u0022http:\/\/www.eas.gatech.edu\/\u0022\u003ESchool of Earth and Atmospheric Sciences\u003C\/a\u003E at the Georgia Institute of Technology. \u201cThis record will provide a new piece of the puzzle from the tropical Pacific showing us how that climate system has responded to forcing events over the past 100,000 years.\u201d\u003C\/p\u003E\u003Cp\u003EAmong the findings were some surprises that show just how complicated the Earth\u2019s climate system can be. While the stalagmite record reflected responses to abrupt changes known as Heinrich events, another major type of event \u2013 known as Dansgaard-Oeschger excursions \u2013 left no evidence in the Borneo stalagmites. Both types of abrupt climate change events are prominently featured in a previously-published stalagmite climate record from China \u2013 which is only slightly north of Borneo.\u003C\/p\u003E\u003Cp\u003E\u201cTo my knowledge, this is the first record that so clearly shows sensitivity to one set of major abrupt climate change events and not another,\u201d said Cobb. \u201cThese two types of abrupt change events appear to have different degrees of tropical Pacific involvement, and because the tropical Pacific speaks with such a loud voice when it does speak, we think this is extremely important for understanding the mechanisms underlying these events.\u201d\u003C\/p\u003E\u003Cp\u003EThe researchers were also surprised to discover a very large and abrupt signal in their stalagmite climate records precisely when super-volcano Toba erupted nearby, roughly 74,000 years ago.\u003C\/p\u003E\u003Cp\u003EThe team recovered the stalagmites from caves in Gunung Mulu and Gunung Buda National Parks, in northern Borneo, which is located a few degrees north of the Equator in the western Pacific. Back at their Georgia Tech lab, they analyzed the stalagmites for the ratio of oxygen isotopes contained in samples of calcium carbonate, the material from which the stalagmites were formed. That ratio is set by the oxygen isotopes in rainfall at the site, as the water that seeped into the ground dissolved limestone rock and dripped into the caves to form the stalagmites. The stalagmites accumulate at a rate of roughly one centimeter every thousand years.\u003C\/p\u003E\u003Cp\u003E\u201cStalagmites are time capsules of climate signals from thousands of years in the past,\u201d said Stacy Carolin, a Georgia Tech Ph.D. candidate who gathered and analyzed the stalagmites. \u201cWe have instrumental records of climate only for the past 100 years or so, and if we want to look deeper into the past, we have to find records like these that locked in climate signals we can extract today.\u201d\u003C\/p\u003E\u003Cp\u003EIn the laboratory, Carolin sawed each stalagmite in half, opening it like a hot dog bun. She then used a tiny drill bit to take samples of the calcium carbonate down the center at one-millimeter steps. Because the stalagmites grew at varying rates, each sample represented as little as 60 years of time, or as much as 200 years. The precise ages of the samples were determined by measuring uranium and thorium isotope ratios, an analysis done with the help of Jess F. Adkins, a professor at the California Institute of Technology and a co-author of the study.\u003C\/p\u003E\u003Cp\u003ERainfall oxygen isotopic ratios are good indicators of the amount of rainfall occurring throughout the region, as determined by a modern-day calibration study recently published by another graduate student in Cobb\u2019s lab.\u003C\/p\u003E\u003Cp\u003EMerging data from the four different stalagmites provided a record of precipitation trends in the western Pacific over the past 100,000 years. That information can be compared to stalagmite and ice core climate records obtained elsewhere in the world.\u003C\/p\u003E\u003Cp\u003E\u201cThis record, which spans the entire last glacial period, adds significantly to the understanding of how various climate forcings are felt by the western tropical Pacific,\u201d Carolin added.\u003Cbr \/\u003EClimate scientists are interested in learning more about abrupt climate changes because they indicate that the climate system may have \u201ctipping points.\u201d So far, the climate system has responded to rising carbon dioxide levels at a fairly steady rate, but many scientists worry about possible nonlinear effects.\u003C\/p\u003E\u003Cp\u003E\u201cAs a society, we haven\u2019t really thought enough about the fact that we are moving Earth\u2019s climate system toward a new state very quickly,\u201d said Cobb. \u201cIt\u2019s important to remember that the climate system has important nonlinearities that are most evident in these abrupt climate events. Ultimately, we\u2019d like to be able to reproduce the global signatures of these abrupt climate events with numerical models of the climate system, and investigate the physics that drive such events.\u201d\u003C\/p\u003E\u003Cp\u003EFor Carolin, studying the half-meter-long stalagmites brought an awareness that the Earth has not always been as we know it today.\u003C\/p\u003E\u003Cp\u003E\u201cYou have to be impressed with the scope of what you are studying, and recognize that the state our climate is in today is incredibly different from Earth\u2019s climate during the last Ice Age,\u201d she said. \u201cAs we consider how humans may be affecting climate, dissecting what was going on tens of thousands of years ago in all regions of the globe can help scientists better predict how the Earth will respond to modern climate forcings.\u201d\u003C\/p\u003E\u003Cp\u003EIn addition to those already mentioned, the research team included Brian Clark, manager of the Gunung Mulu National Park where the samples were gathered; Syria Lejau and Jenny Malang, Gunung Mulu cave guides who aided in sample collection; Jessica Conroy, a Georgia Tech postdoctoral fellow; and Andrew Tuen, a professor at the Universiti Malaysia Sarawak.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was funded by the National Science Foundation through PECASE Award ATM-0645291. The findings and conclusions are those of the authors and do not necessarily represent the official views of the NSF.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: Stacy A. Carolin, et al., \u201cVaried response of western Pacific hydrology to climate forcings over the last glacial period,\u201d (Science 2013).\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia\u0026nbsp; 30332-0181\u0026nbsp; USA\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (404-894-6986)(\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E)\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EA new set of long-term climate records based on cave stalagmites collected from tropical Borneo shows that the western tropical Pacific responded very differently than other regions of the globe to abrupt climate change events. The 100,000-year climate record adds to data on past climate events, and may help scientists assess models designed to predict how the Earth\u2019s climate will respond in the future.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Climate records from cave stalagmites show that the western tropical Pacific responded differently to abrupt climate change events."}],"uid":"27303","created_gmt":"2013-06-06 13:56:31","changed_gmt":"2016-10-08 03:14:20","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2013-06-06T00:00:00-04:00","iso_date":"2013-06-06T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"216701":{"id":"216701","type":"image","title":"Cobweb Cave","body":null,"created":"1449180114","gmt_created":"2015-12-03 22:01:54","changed":"1475894882","gmt_changed":"2016-10-08 02:48:02","alt":"Cobweb 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