Den lille istid

Den lille istid (international forkortelse: LIA) var en køligere periode, som begyndte i senmiddelalderen og sluttede i 1800-tallet. Hvornår temperatursænkningen begyndte, er der ingen konsensus omkring. Der er blevet påvist tre tidspunkter, hvor temperaturen nåede et minimum i perioden, ét omkring 1660, ét 1770 og ét omkring 1850. Den lille istid var ikke en konstant kold periode, men gav forskellige udslag til forskellige tider på forskellige steder på Jorden; noget tyder dog på, at den nordlige halvkugle blev mest ramt, og udsvingene var størst om vinteren. Den lille istid optræder efter middelalderlige varmeperiode.

De første indikationer om en usædvanlig kuldeperiode er fundet i almanakker, som beskriver kølige og regnfulde somre. Ligeledes forekommer helt tilfrosne søer og floder oftere på billeder, end de har gjort senere.

Efter den første påvisning af Den lille istid blev det antaget, at det et var globalt fænomen, men det anses i dag for at være mere usikkert.^[1]

Ifølge forskning fra 2021 af Francois Lapointe og Raymond S. Bradley kollapsede Atlantic meridional overturning circulation (AMOC), inkl. Golfstrømmen, i slutningen af det 13. århundrede, hvilket forårsagede den lille istid.^[2]^[3]

^ "www.grida.no". Arkiveret fra originalen 29. maj 2006. Hentet 12. juni 2006.
^ December 18, 2021, scitechdaily.com: Winter Is Coming Paradox: Researchers Uncover the Surprising Cause of the Little Ice Age Citat: "...But in the late 1300s, AMOC strengthened significantly, which meant that far more warm water than usual was moving north, which in turn cause rapid Arctic ice loss. Over the course of a few decades in the late 1300s and 1400s, vast amounts of ice were flushed out into the North Atlantic, which not only cooled the North Atlantic waters, but also diluted their saltiness, ultimately causing AMOC to collapse. It is this collapse that then triggered a substantial cooling..."
^ 15 Dec 2021, science.org: Little Ice Age abruptly triggered by intrusion of Atlantic waters into the Nordic Seas Citat: "...Here, we show that the LIA was preceded by an exceptional intrusion of warm Atlantic water into the Nordic Seas in the late 1300s...", backup

[1] "www.grida.no". Arkiveret fra originalen 29. maj 2006. Hentet 12. juni 2006.

[2] December 18, 2021, scitechdaily.com: Winter Is Coming Paradox: Researchers Uncover the Surprising Cause of the Little Ice Age Citat: "...But in the late 1300s, AMOC strengthened significantly, which meant that far more warm water than usual was moving north, which in turn cause rapid Arctic ice loss. Over the course of a few decades in the late 1300s and 1400s, vast amounts of ice were flushed out into the North Atlantic, which not only cooled the North Atlantic waters, but also diluted their saltiness, ultimately causing AMOC to collapse. It is this collapse that then triggered a substantial cooling..."

[3] 15 Dec 2021, science.org: Little Ice Age abruptly triggered by intrusion of Atlantic waters into the Nordic Seas Citat: "...Here, we show that the LIA was preceded by an exceptional intrusion of warm Atlantic water into the Nordic Seas in the late 1300s...", backup

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Den lille istid

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