{"270171":{"#nid":"270171","#data":{"type":"news","title":"Study of Fossilized Shells Finds Little Evidence of Icebergs\u2019 Influence on Ice Age Ocean Circulation","body":[{"value":"\u003Cp\u003EDuring the last North American ice age, large numbers of icebergs calved from the North American ice sheet and plunged into the North Atlantic Ocean. Scientists have thought that these iceberg surges disrupted a key ocean circulation pattern, but a new study found little evidence of a disruption during some of the major iceberg surges.\u003C\/p\u003E\u003Cp\u003EUnderstanding the controls on and the stability of this ocean circulation system could help scientists better assess this system\u2019s vulnerability to future climate change.\u003C\/p\u003E\u003Cp\u003EThese major iceberg surges are known as Heinrich events. While the study found evidence that some Heinrich events had a major impact on the system of ocean currents that transfer heat from the Southern to the Northern Hemisphere (Atlantic Meridional Overturning Circulation, or AMOC), the study found little evidence of major changes to the AMOC for two of the Heinrich Events that occurred earlier, at the height of the last ice age, at about 24,000 and 31,000 years ago. \u003C\/p\u003E\u003Cp\u003E\u201cThat\u2019s surprising, you would expect to see disruption for all of the Heinrich events,\u201d said Jean \u003Ca href=\u0022http:\/\/shadow.eas.gatech.edu\/~jean\/\u0022\u003ELynch-Stieglitz\u003C\/a\u003E, a professor in the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology in Atlanta, and the study\u2019s lead author. \u201cWe just didn\u2019t see any indication that anything out of the ordinary was going on during those previous Heinrich events.\u201d\u003C\/p\u003E\u003Cp\u003EThe study was published January 12 in the journal \u003Ca href=\u0022http:\/\/dx.doi.org\/10.1038\/NGEO2045\u0022\u003E\u003Cem\u003ENature Geoscience\u003C\/em\u003E\u003C\/a\u003E and was supported by the National Science Foundation (NSF). One of the paper\u2019s co-authors, L. Gene Henry, was an undergraduate at Georgia Tech during the research project. \u003C\/p\u003E\u003Cp\u003EThe study\u2019s findings suggest that the broader climate changes seen at the time of the Heinrich events \u2014 changes in precipitation at lower latitudes, for example \u2014 may not be linked in a direct, simple way to the AMOC. \u003C\/p\u003E\u003Cp\u003ETo examine the impact of Heinrich events on this ocean circulation, the researchers travelled to the Florida Straits, where they took sediment cores from the ocean floor. They analyzed the fossilized shells of a bottom dwelling single celled organisms (\u003Cem\u003Eforaminifera\u003C\/em\u003E) for specific oxygen and carbon isotope ratios. These isotopes provide valuable information about the properties of the seawater in the Florida Straits at the time when these small shells were formed over the past 35,000 years. \u003C\/p\u003E\u003Cp\u003E\u201cSurprisingly, it\u2019s been very, very difficult to get good records of the past variability of the overturning circulation on these time scales,\u201d Lynch-Stieglitz said. \u003C\/p\u003E\u003Cp\u003EPrevious studies have examined the influence of Heinrich events on the AMOC, but the results have been conflicting. Most of the previous studies examined carbon isotopes in deep water \u003Cem\u003Eforaminifera\u003C\/em\u003E. Lynch-Stieglitz\u2019s team used a new approach to the problem by examining the upper part of the overturning circulation. The research team also used computer models to show the sensitivity of the seawater properties at these shallower depths to changes in ocean circulation.\u003C\/p\u003E\u003Cp\u003E\u201cUnderstanding the controls on and the stability of this circulation system will ultimately help scientists to better assess the AMOC\u2019s vulnerability to future climate change,\u201d Lynch-Stieglitz said.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research is supported by the National Science Foundation (NSF) under award number OCE-0096472, OCE-0648258, and OCE-1102743. Any conclusions or opinions 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: Jean Lynch-Stieglitz, et al., \u0022Muted change in Atlantic overturning circulation over some glacial-aged Heinrich Events,\u0022 (\u003Cem\u003ENature Geoscience\u003C\/em\u003E, January 2014). (\u003Ca href=\u0022http:\/\/dx.doi.org\/10.1038\/NGEO2045\u0022\u003Ehttp:\/\/dx.doi.org\/10.1038\/NGEO2045\u003C\/a\u003E).\u003C\/p\u003E\u003Cp\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 30332-0181 USA\u003C\/strong\u003E\u003Cbr \/\u003E\u003Ca href=\u0022https:\/\/twitter.com\/GTResearchNews\u0022\u003E\u003Cstrong\u003E@GTResearchNews\u003C\/strong\u003E\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts:\u003C\/strong\u003E Brett Israel (404-385-1933) (\u003Ca href=\u0022mailto:brett.israel@comm.gatech.edu\u0022\u003Ebrett.israel@comm.gatech.edu\u003C\/a\u003E)(\u003Ca href=\u0022https:\/\/twitter.com\/btiatl\u0022\u003E@btiatl\u003C\/a\u003E) or 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 Brett Israel\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EDuring the last North American ice age, large numbers of icebergs calved from the North American ice sheet and plunged into the North Atlantic Ocean. Scientists have thought that these iceberg surges disrupted a key ocean circulation pattern, but a new study found little evidence of a disruption during some of the major iceberg surges.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Scientists have thought that large iceberg surges disrupted a key ocean circulation pattern during the last North American ice age, but a new study found little evidence of a disruption during some of the major iceberg surges."}],"uid":"27902","created_gmt":"2014-01-22 11:27:56","changed_gmt":"2016-10-08 03:15:44","author":"Brett Israel","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2014-01-22T00:00:00-05:00","iso_date":"2014-01-22T00:00:00-05:00","tz":"America\/New_York"},"extras":[],"hg_media":{"270151":{"id":"270151","type":"image","title":"Analyzing fossilized shells","body":null,"created":"1449244077","gmt_created":"2015-12-04 15:47:57","changed":"1475894959","gmt_changed":"2016-10-08 02:49:19","alt":"Analyzing fossilized shells","file":{"fid":"198614","name":"fossilized_shells.jpg","image_path":"\/sites\/default\/files\/images\/fossilized_shells_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/fossilized_shells_0.jpg","mime":"image\/jpeg","size":82934,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/fossilized_shells_0.jpg?itok=D-IK1SY4"}},"270141":{"id":"270141","type":"image","title":"Sectioning sediment cores","body":null,"created":"1449244077","gmt_created":"2015-12-04 15:47:57","changed":"1475894959","gmt_changed":"2016-10-08 02:49:19","alt":"Sectioning sediment cores","file":{"fid":"198613","name":"sediment_core_sectioning.jpg","image_path":"\/sites\/default\/files\/images\/sediment_core_sectioning_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/sediment_core_sectioning_0.jpg","mime":"image\/jpeg","size":137248,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/sediment_core_sectioning_0.jpg?itok=XAMTgBvv"}}},"media_ids":["270151","270141"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"154","name":"Environment"}],"keywords":[],"core_research_areas":[],"news_room_topics":[{"id":"71911","name":"Earth and Environment"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EBrett Israel\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:brett.israel@comm.gatech.edu\u0022\u003Ebrett.israel@comm.gatech.edu\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E404-385-1933\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022https:\/\/twitter.com\/btiatl\u0022\u003E@btiatl\u003C\/a\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["brett.israel@comm.gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}