NORthern constraints on the Atlantic ThermoHaline circulation

Golfstrømmens forlengelse mot Arktis holder Norskehavet og store deler av Barentshavet isfritt. Dette er en forutsetning for vårt milde klima og rike tilgang til marine ressurser, en bærebjelke for norsk velstand og egenart. NORTH er en overordnet og nyskapende tilnærming til både å forstå og tallfeste endringer i denne livgivende havstrømmen. Prosjektet er basert på en helhetlig tilnærming der både teori, observasjoner, numeriske modeller og laboratorieeksperiment kombineres for å beskrive hva som begrenser havsirkulasjonen her i nord, hvordan denne vekselvirker med klima, og i hvilken grad disse vekselvirkningene faktisk er forutsigbare måneder til år i forveien. Viktige resultat siste periode inkluderer: + to fullførte PhD-grader, Lambert (2017) og Onarheim (2017), på henholdsvis struktur og stabilitet av Golfstrømmens nordlige gren; og hvordan isdekket endrer seg i Arktis, nå og i framtiden. + Bringedal et al. (2018) dokumenterer - fra observasjoner - et stabilt Golfstrøm-system mellom Nordatlanteren og Norskehavet + Onarheim et al. (2018) viser hvordan isen trekker seg tilbake for hver måned og i hvert regionale havområde.

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The Atlantic Ocean's thermohaline circulation (THC) is an important and dynamically active modulator of global climate. Its northern limb - the scope of NORTH - extends through the Nordic Seas and the cold Arctic, a region that appears to be particularly influenced by climate change. NORTH constitutes a comprehensive and novel approach to understand and quantify the structure and variance of northern THC. NORTH is based on a coherent framework of theory development, observations, laboratory experiments, a nd ocean/climate general circulation models. The theory in particular assesses the THC's combined sensitivity to change in heat loss and freshwater input, a complexity that is presently unresolved. This sensitivity is decisive for constraining the structu re and variance of future THC and climate as both the Earth's poleward heat transport and hydrological cycle are expected to change in quantity and quality with projected global warming. Our theoretical considerations also target the active role of the at mosphere and possible feedbacks involving northern THC. Two independent avenues of research complement the theoretical approach - laboratory experiments and ocean/climate general circulation model (GCM) simulations. The laboratory provides both evaluation of theory and an intuitive and attractive vehicle for teaching and interaction with the general public. Theory is projected on model simulations, in general not to "validate" theory (which may or may not be more true to nature than a given GCM), but as a novel framework for objectively quantifying simulated THC structure and variance - including contrasting historical and projected climate.