Hem
Illustrationsbild. (AP)

30 miljoner ton is smälter varje timme på Grönland

Det grönländska istäcket smälter bort i en hastighet av 30 miljoner ton per timme på grund av klimatförändringar – en 20 procents högre avsmältningstakt än tidigare trott, visar en ny studie enligt The Guardian.

Forskare fruktar nu att det ökade flödet av färskvatten ut i norra Atlanten kan innebära att havsströmmen Amoc kommer närmare en kollaps, vilket skulle få enorm påverkan på klimatet – inte minst i norra Europa.

– Förändringarna runt Grönland är oerhörda och sker överallt – nästan varje glaciär har dragit sig tillbaka under de gångna årtiondena, säger Nasaforskaren Chad Greene som lett studien.

bakgrund
 
Atlantic meridional overturning circulation
Wikipedia (en)
The Atlantic meridional overturning circulation (AMOC) is part of a global thermohaline circulation in the oceans and is the zonally integrated component of surface and deep currents in the Atlantic Ocean. It is characterized by a northward flow of warm, salty water in the upper layers of the Atlantic, and a southward flow of colder, deep waters. These "limbs" are linked by regions of overturning in the Nordic and Labrador Seas and the Southern Ocean, although the extent of overturning in the Labrador Sea is disputed. The AMOC is an important component of the Earth's climate system, and is a result of both atmospheric and thermohaline drivers. Climate change has the potential to weaken the AMOC through increases in ocean heat content and elevated freshwater flows from the melting ice sheets. Oceanographic reconstructions generally suggest that the AMOC is already weaker than it was before the Industrial Revolution, although there is a robust debate over the role of anthropogenic climate change versus the circulation's century-scale and millennial-scale variability. Climate models consistently project that the AMOC would weaken further over the 21st century,: 19  which would affect average temperature over areas like Scandinavia and Britain that are warmed by the North Atlantic drift, as well as accelerate sea level rise around North America and reduce primary production in the North Atlantic.Severe weakening of the AMOC has the potential to cause an outright collapse of the circulation, which would not be easily reversible and thus constitute one of the tipping points in the climate system. A shutdown would have far greater impacts than a slowdown on both the marine and some terrestrial ecosystems: it would lower the average temperature and precipitation in Europe, slashing the region's agricultural output, and may have a substantial effect on extreme weather events. Earth system models used in Coupled Model Intercomparison Project indicate that shutdown is only likely after high levels of warming are sustained well after 2100, but they have been criticized by some researchers for what they saw as excessive stability, and a number of lower-complexity studies argue that a collapse can happen considerably earlier. One of those lower-complexity projections suggests that AMOC collapse could happen around 2057, but many scientists are skeptical of the claim. On the other hand, paleoceanographic research suggests that the AMOC may be even more stable than what is predicted by most models.

Gå förbi betalväggar!

Omni Mer låser upp en mängd artiklar. En smidig lösning när du vill fördjupa dig.

Omni är politiskt obundna och oberoende. Vi strävar efter att ge fler perspektiv på nyheterna. Har du frågor eller synpunkter kring vår rapportering? Kontakta redaktionen