Editing Ice age (section)

===Fluctuations in ocean currents===
Another important contribution to ancient climate regimes is the variation of ocean currents, which are modified by continent position, sea levels and salinity, as well as other factors. They have the ability to cool (e.g. aiding the creation of Antarctic ice) and the ability to warm (e.g. giving the British Isles a temperate as opposed to a boreal climate). The closing of the [[Isthmus of Panama]] about 3 million years ago may have ushered in the present period of strong glaciation over North America by ending the exchange of water between the tropical Atlantic and Pacific Oceans.<ref>{{cite journal |url=http://discovermagazine.com/1996/apr/weareallpanamani743 |title=We are all Panamanians |author=Svitil, K. A. |date=April 1996 |journal=Discover |access-date=2012-04-23 |archive-date=2014-02-03 |archive-url=https://web.archive.org/web/20140203183832/http://discovermagazine.com/1996/apr/weareallpanamani743 |url-status=live }}—formation of Isthmus of Panama may have started a series of climatic changes that led to evolution of hominids</ref>

Analyses suggest that ocean current fluctuations can adequately account for recent glacial oscillations. During the last glacial period the sea-level fluctuated 20–30&nbsp;m as water was sequestered, primarily in the [[Northern Hemisphere]] ice sheets. When ice collected and the sea level dropped sufficiently, flow through the [[Bering Strait]] (the narrow strait between Siberia and Alaska is about 50&nbsp;m deep today) was reduced, resulting in increased flow from the North Atlantic. This realigned the [[thermohaline circulation]] in the Atlantic, increasing heat transport into the Arctic, which melted the polar ice accumulation and reduced other continental ice sheets. The release of water raised sea levels again, restoring the ingress of colder water from the Pacific with an accompanying shift to northern hemisphere ice accumulation.<ref name=Hu2010>{{Cite journal |last1=Hu |first1=Aixue |last2=Meehl |first2=Gerald A. |author2-link=Gerald Meehl |last3=Otto-Bliesner |first3=Bette L. |author-link3=Bette Otto-Bliesner |last4=Waelbroeck |first4=Claire |author5=Weiqing Han |last6=Loutre |first6=Marie-France |last7=Lambeck |first7=Kurt |last8=Mitrovica |first8=Jerry X. |last9=Rosenbloom |first9=Nan |title=Influence of Bering Strait flow and North Atlantic circulation on glacial sea-level changes |journal=Nature Geoscience |volume=3 |issue=2 |pages=118–121 |year=2010 |doi=10.1038/ngeo729 |bibcode=2010NatGe...3..118H |hdl=1885/30691 |url=http://www.cgd.ucar.edu/ccr/publications/ngeo729.pdf |citeseerx=10.1.1.391.8727 |access-date=2017-10-24 |archive-date=2017-08-11 |archive-url=https://web.archive.org/web/20170811021943/http://www.cgd.ucar.edu/ccr/publications/ngeo729.pdf |url-status=dead }}</ref>

According to a study published in ''[[Nature (journal)|Nature]]'' in 2021, all [[glacial period]]s of ice ages over the last 1.5 million years were associated with northward shifts of melting Antarctic icebergs which changed ocean circulation patterns, [[Oceanic carbon cycle|leading to more CO<sub>2</sub> being pulled out of the atmosphere]]. The authors suggest that this process may be disrupted in the future as the [[Southern Ocean]] will become too warm for the icebergs to travel far enough to trigger these changes.<ref>{{cite news |title=Melting icebergs key to sequence of an ice age, scientists find |url=https://phys.org/news/2021-01-icebergs-key-sequence-ice-age.html |access-date=12 February 2021 |work=phys.org |language=en |archive-date=27 January 2021 |archive-url=https://web.archive.org/web/20210127163116/https://phys.org/news/2021-01-icebergs-key-sequence-ice-age.html |url-status=live }}</ref><ref>{{cite journal |last1=Starr |first1=Aidan |last2=Hall |first2=Ian R. |last3=Barker |first3=Stephen |last4=Rackow |first4=Thomas |last5=Zhang |first5=Xu |last6=Hemming |first6=Sidney R. |last7=Lubbe |first7=H. J. L. van der |last8=Knorr |first8=Gregor |last9=Berke |first9=Melissa A. |last10=Bigg |first10=Grant R. |last11=Cartagena-Sierra |first11=Alejandra |last12=Jiménez-Espejo |first12=Francisco J. |last13=Gong |first13=Xun |last14=Gruetzner |first14=Jens |last15=Lathika |first15=Nambiyathodi |last16=LeVay |first16=Leah J. |last17=Robinson |first17=Rebecca S. |last18=Ziegler |first18=Martin |title=Antarctic icebergs reorganize ocean circulation during Pleistocene glacials |journal=Nature |date=January 2021 |volume=589 |issue=7841 |pages=236–241 |doi=10.1038/s41586-020-03094-7 |pmid=33442043 |bibcode=2021Natur.589..236S |hdl=10261/258181 |s2cid=231598435 |url=https://www.nature.com/articles/s41586-020-03094-7 |access-date=12 February 2021 |language=en |issn=1476-4687 |hdl-access=free |archive-date=4 February 2021 |archive-url=https://web.archive.org/web/20210204185828/https://www.nature.com/articles/s41586-020-03094-7 |url-status=live }}</ref>