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POLARPROG-Polarforskningsprogram

Wave-mediated atmosphere-ocean-sea-ice interactions and their climatic impacts in the Nordic Seas and eastern Arctic

Alternative title: Bølgepåvirkning av atmosfære-hav-sjøis interaksjoner og deres virkning på klimaet i de nordiske hav og østlige Arktis

Awarded: NOK 11.9 mill.

Project Manager:

Project Number:

325654

Application Type:

Project Period:

2021 - 2025

Funding received from:

Wind generated ocean surface waves are the waves we can see breaking on the beach or those waves that make us sea-sick when traveling in a boat. They are always present on the surface of the ocean. These waves have periods from seconds to a couple a minutes with wavelengths from centimeters up to approx. 500 meters. Their height can be from centimeters up to 15 meters or more. These waves are on the interface between ocean and atmosphere and affect the fluxes of momentum and energy, heat mass and radiation. Observations have also shown intense interaction between waves and sea ice. Because of the  scales of the waves it was thought that their influence was felt only locally and that their effects on ocean and atmosphere could be well described as a function of wind speed only. This simplified view has been questioned recently since some of the waves do not travel in the same direction as the wind (named swell). In this project we have included active (in contrast with parametrizations) ocean surface waves in a climate model: Norwegian Earth System Model (NorESM) to study their influence in the climate. We will analyze first the interactions of each component (atmosphere, ocean and sea-ice) with the waves before using all the interactions at the same time. As preliminary results we have found that including a mutual interaction between the waves and the atmosphere (coupling wave-atmosphere) improves the storm's localization which increases the amount of oceanic heat taken up by the atmosphere and as a result more atmospheric heat is sent to the Arctic. We have also found that the mutual interaction between the waves and the ocean (coupling wave-ocean) mainly deepens the ocean mixed layer depth via the so-called Langmuir circulation.

The North Atlantic - Arctic Ocean is a key region of the global Northern-Hemisphere storm track, characterized by strong air-sea exchange and associated meridional flux of enthalpy and water vapour. Regionally it determines much of the climate of western Eurasia and of the Nordic Seas, with strong effects on the Arctic sea-ice cover. The ocean state in particular is affected not only by the effects of strong diabatic and mechanical forcing, but notably also by the large activity of surface waves forced by the intense storms. Even though it is expected that the presence of surface waves has an important impact on the coupling between atmosphere, ocean, and sea ice, to date there is no quantitative assessment on the implications for the climate of the European/North-Atlantic region and for its evolution under natural or anthropogenic forcing. Indeed, surface waves are at present excluded from the representation of surface interactions in Earth System Models (ESMs). To understand the implications of this, we will, for the first time, use an ESM with a fully coupled wave model covering the northern North Atlantic - Arctic domain to carry out a systematic study of the effects of full coupling between ocean surface waves, atmosphere, ocean, and sea-ice on the climate in the Nordic Seas and eastern Arctic region. The project will thereby go beyond the state of the art and provide the scientific justification for a next generation ESM with a fully coupled wave model in the global domain. The rationale for a regional focus is two-fold. The first concerns the critical role of the marginal ice zone on the Northern-Hemisphere climate, an area that is particularly exposed to the effects of global warming and intrinsically exposed to wave action. The second rationale concerns the scientific prioritization of model development paths for the next-generation Norwegian Earth System Model. Understanding regional effects is a prerequisite to evaluate potential global climate impacts.

Funding scheme:

POLARPROG-Polarforskningsprogram