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Freshening of the labrador sea as a trigger for little ice age development

2017-04Journal article Open access
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dc.contributor.authorAlonso-Garcia, Montserrat
dc.contributor.authorKleiven, Helga (Kikki) F.
dc.contributor.authorMcManus, Jerry F.
dc.contributor.authorMoffa-Sanchez, Paola
dc.contributor.authorBroecker, Wallace S.
dc.contributor.authorFlower, Benjamin P.
dc.date.accessioned2018-12-07T14:52:35Z
dc.date.available2018-12-07T14:52:35Z
dc.date.issued2017-04
dc.description.abstractArctic freshwater discharges to the Labrador Sea from melting glaciers and sea ice can have a large impact on ocean circulation dynamics in the North Atlantic, modifying climate and deep water formation in this region. In this study, we present for the first time a high resolution record of ice rafting in the Labrador Sea over the last millennium to assess the effects of freshwater discharges in this region on ocean circulation and climate. The occurrence of ice-rafted debris (IRD) in the Labrador Sea was studied using sediments from Site GS06-144-03 (57.29 degrees N, 48.37 degrees W; 3432 m water depth). IRD from the fraction 63-150 mu m shows particularly high concentrations during the intervals similar to AD 1000-1100, similar to 1150-1250, similar to 1400-1450, similar to 1650-1700 and similar to 1750-1800. The first two intervals occurred during the Medieval Climate Anomaly (MCA), whereas the others took place within the Little Ice Age (LIA). Mineralogical identification indicates that the main IRD source during the MCA was SE Greenland. In contrast, the concentration and relative abundance of hematite-stained grains reflects an increase in the contribution of Arctic ice during the LIA. The comparison of our Labrador Sea IRD records with other climate proxies from the subpolar North Atlantic allowed us to propose a sequence of processes that led to the cooling that occurred during the LIA, particularly in the Northern Hemisphere. This study reveals that the warm cli- mate of the MCA may have enhanced iceberg calving along the SE Greenland coast and, as a result, freshened the subpolar gyre (SPG). Consequently, SPG circulation switched to a weaker mode and reduced convection in the Labrador Sea, decreasing its contribution to the North Atlantic deep water formation and, thus, reducing the amount of heat transported to high latitudes. This situation of weak SPG circulation may have made the North Atlantic climate more unstable, inducing a state in which external forcings (e.g. reduced solar irradiance and volcanic eruptions) could easily drive periods of severe cold conditions in Europe and the North Atlantic like the LIA. This analysis indicates that a freshening of the SPG may play a crucial role in the development of cold events during the Holocene, which may be of key importance for predictions about future climate.
dc.description.sponsorshipNSF [OCE-0961670, OCE-1258984]; Comer Science and Education Foundation [CP75]; Portuguese National Science and Technology Foundation (FCT) [SFRH/BPD/96960/2013]; CCMAR funds [UID/Multi/04326/2013]; NSF [OCE-0961670, OCE-1258984]; Comer Science and Education Foundation [CP75]; Portuguese National Science and Technology Foundation (FCT) [SFRH/BPD/96960/2013]; CCMAR funds [UID/Multi/04326/2013]
dc.description.versioninfo:eu-repo/semantics/publishedVersion
dc.identifier.doi10.5194/cp-13-317-2017
dc.identifier.issn1814-9324
dc.identifier.issn1814-9332
dc.identifier.urihttp://hdl.handle.net/10400.1/11132
dc.language.isoeng
dc.peerreviewedyes
dc.publisherCopernicus Gesellschaft Mbh
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.subjectSubpolar North-Atlantic
dc.subjectLast 2000 years
dc.subjectSurface temperatures
dc.subjectClimate variability
dc.subjectArctic oscillation
dc.subjectGreenland shelf
dc.subjectCirculation
dc.subjectHolocene
dc.subjectIceland
dc.subjectOcean
dc.titleFreshening of the labrador sea as a trigger for little ice age development
dc.typejournal article
dspace.entity.typePublication
oaire.awardURIinfo:eu-repo/grantAgreement/FCT/5876/UID%2FMulti%2F04326%2F2013/PT
oaire.citation.endPage331
oaire.citation.issue4
oaire.citation.startPage317
oaire.citation.titleClimate of the Past
oaire.citation.volume13
oaire.fundingStream5876
person.familyNameAlonso-Garcia
person.givenNameMontserrat
person.identifier.ciencia-id5B1B-33EE-50B9
person.identifier.orcid0000-0002-0241-2178
person.identifier.scopus-author-id51565655800
project.funder.identifierhttp://doi.org/10.13039/501100001871
project.funder.nameFundação para a Ciência e a Tecnologia
rcaap.rightsopenAccess
rcaap.typearticle
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relation.isAuthorOfPublication.latestForDiscovery7772f374-a9c2-41e7-a798-4d811b8a9a48
relation.isProjectOfPublication868b4818-3efa-4edb-9202-c464d64fd38f
relation.isProjectOfPublication.latestForDiscovery868b4818-3efa-4edb-9202-c464d64fd38f

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