North Atlantic Current: Difference between revisions

[[File:North Atlantic currents.svg|thumb|The North Atlantic Current is the first leg in the North Atlantic Subpolar Gyre.]]

Unlike the [[AMOC]], the observations of Labrador Sea outflow showed no negative trend from 1997 to 2009,<ref>{{Cite journal |last1=Fischer |first1=Jürgen |last2=Visbeck |first2=Martin |last3=Zantopp |first3=Rainer |last4=Nunes |first4=Nuno |date=31 December 2010 |title=Interannual to decadal variability of outflow from the Labrador Sea |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2010GL045321 |journal=Geophysical Research Letters |volume=37 |issue=24 |pages=3204–3210 |doi=10.1029/2010GL045321 |bibcode=2010GeoRL..3724610F |s2cid=54768522 |accessdoi-dateaccess=3 Octoberfree 2022}}</ref> and the Labrador Sea convection began to intensify in 2012, reaching a new high in 2016.<ref>{{Cite journal |last1=Yashayaev |first1=Igor |last2=Loder |first2=John W. |date=8 December 2016 |title=Further intensification of deep convection in the Labrador Sea in 2016 |journal=Geophysical Research Letters |volume=44 |issue=3 |pages=1429–1438 |doi=10.1002/2016GL071668 |s2cid=133577687 |doi-access=free }}</ref> As of 2022, the trend of strengthened Labrador Sea convection appears to hold, and is associated with observed increases in [[marine primary production]].<ref>{{Cite journal |last1=Tesdal |first1=Jan-Erik |last2=Ducklow |first2=Hugh W. |last3=Goes |first3=Joaquim I. |last4=Yashayaev |first4=Igor |date=August 2022 |title=Recent nutrient enrichment and high biological productivity in the Labrador Sea is tied to enhanced winter convection |journal=Geophysical Research Letters |volume=44 |issue=3 |page=102848 |doi=10.1016/j.pocean.2022.102848 |bibcode=2022PrOce.20602848T |s2cid=249977465 |doi-access=free }}</ref> Yet, a 150-year dataset suggests that even this recently strengthened convection is anomalously weak compared to its baseline state.<ref>{{Cite journal |last1=Thornalley |first1=David JR |display-authors=etal |date=11 April 2018 |title=Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years |url=https://www.nature.com/articles/s41586-018-0007-4 |journal=Nature |volume=556 |issue=7700 |pages=227–230 |doi=10.1038/s41586-018-0007-4 |pmid=29643484 |bibcode=2018Natur.556..227T |s2cid=4771341 |access-date=3 October 2022}}</ref>

Some [[climate model]]s indicate that the deep convection in [[Labrador Sea|Labrador]]-[[Irminger Sea|Irminger]] Seas could collapse under certain [[global warming]] scenarios, which would then collapse the entire circulation in the North [[subpolar gyre]]. It is considered unlikely to recover even if the temperature is returned to a lower level, making it an example of a climate tipping point. This would result in rapid cooling, with implications for economic sectors, agriculture industry, water resources and energy management in Western Europe and the East Coast of the United States.<ref>{{cite journal|title=Abrupt cooling over the North Atlantic in modern climate models|journal=Nature Communications|volume=8|doi=10.1038/ncomms14375|pmid=28198383|pmc=5330854|author=Sgubin |display-authors=etal |year=2017 |bibcode=2017NatCo...8.....S }}</ref> Frajka-Williams et al. 2017 pointed out that recent changes in cooling of the subpolar gyre, warm temperatures in the subtropics and cool anomalies over the tropics, increased the spatial distribution of meridional gradient in [[sea surface temperature]]s, which is not captured by the [[AMO Index]].<ref name="Frajka-Williams">{{cite journal|doi=10.1038/s41598-017-11046-x|pmid=28894211|pmc=5593924|author=Eleanor Frajka-Williams |author2=Claudie Beaulieu |author3=Aurelie Duchez|title=Emerging negative Atlantic Multidecadal Oscillation index in spite of warm subtropics|journal=Scientific Reports|volume=7|issue=1|pages=11224|year=2017|bibcode=2017NatSR...711224F}}</ref>

A 2021 study found that this collapse occurs in only four [[CMIP6]] models out of 35 analyzed. However, only 11 models out of 35 can simulate North Atlantic Current with a high degree of accuracy, and this includes all four models which simulate collapse of the subpolar gyre. As the result, the study estimated the risk of an abrupt cooling event over Europe caused by the collapse of the current at 36.4%, which is lower than the 45.5% chance estimated by the previous generation of models <ref>{{Cite journal |last1=Swingedouw |first1=Didier |last2=Bily |first2=Adrien |last3=Esquerdo |first3=Claire |last4=Borchert |first4=Leonard F. |last5=Sgubin |first5=Giovanni |last6=Mignot |first6=Juliette |last7=Menary |first7=Matthew |date=2021 |title=On the risk of abrupt changes in the North Atlantic subpolar gyre in CMIP6 models |url=https://nyaspubs.onlinelibrary.wiley.com/doi/10.1111/nyas.14659 |journal=Annals of the New York Academy of Sciences |volume=1504 |issue=1 |pages=187–201 |doi=10.1111/nyas.14659|pmid=34212391 |bibcode=2021NYASA1504..187S |s2cid=235712017 |hdl=10447/638022 |hdl-access=free }}</ref> In 2022, a paper suggested that previous disruption of subpolar gyre was connected to the [[Little Ice Age]].<ref>{{Cite journal |last1=Arellano-Nava |first1=Beatriz |last2=Halloran |first2=Paul R. |last3=Boulton |first3=Chris A. |last4=Scourse |first4=James |last5=Butler |first5=Paul G. |last6=Reynolds |first6=David J. |last7=Lenton |first7=Timothy |date=25 August 2022 |title=Destabilisation of the Subpolar North Atlantic prior to the Little Ice Age |journal=Nature Communications |volume=13 |issue=1 |page=5008 |doi=10.1038/s41467-022-32653-x |pmid=36008418 |pmc=9411610 |bibcode=2022NatCo..13.5008A }}</ref>

A 2022 [[Science Magazine]] review study on climate tipping points noted that in the scenarios where this convection collapses, it is most likely to be triggered by 1.8 degrees of global warming. However, model differences mean that the required warming may be as low as 1.1 degrees or as high as 3.8 degrees. Once triggered, the collapse of the current would most likely take 10 years from start to end, with a range between 5 and 50 years. The loss of this convection is estimated to lower the global temperature by up to 0.5 degrees, while the [https://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/Sgubin2017_spg_amoc_collapse.jpg/220px-Sgubin2017_spg_amoc_collapse.jpg average temperature in Europecertain regions of the North Atlantic decreases by around 3 degrees]. There are also substantial impacts on regional [[precipitation]].<ref>{{Cite journal |last1=Armstrong McKay |first1=David|last2=Abrams |first2=Jesse |last3=Winkelmann |first3=Ricarda |last4=Sakschewski |first4=Boris |last5=Loriani |first5=Sina |last6=Fetzer |first6=Ingo|last7=Cornell|first7=Sarah |last8=Rockström |first8=Johan |last9=Staal |first9=Arie |last10=Lenton |first10=Timothy |date=9 September 2022 |title=Exceeding 1.5°C global warming could trigger multiple climate tipping points |url=https://www.science.org/doi/10.1126/science.abn7950 |journal=Science |language=en |volume=377 |issue=6611 |pages=eabn7950 |doi=10.1126/science.abn7950 |pmid=36074831 |hdl=10871/131584 |s2cid=252161375 |issn=0036-8075|hdl-access=free }}</ref><ref>{{Cite web |last=Armstrong McKay |first=David |date=9 September 2022 |title=Exceeding 1.5°C global warming could trigger multiple climate tipping points – paper explainer |url=https://climatetippingpoints.info/2022/09/09/climate-tipping-points-reassessment-explainer/ |access-date=2 October 2022 |website=climatetippingpoints.info |language=en}}</ref>