Arctic sea ice decreases; among the causes that have contributed to this recent loss, the poleward heat transport from the North Atlantic Ocean into the Arctic: a topic that we are able to deepen thanks to the innovation developed in the field of modelling and complex systems that can currently simulate the behaviour of the ocean with high precision. A study published on the prestigious journal Climate Dynamics unveils us the details of this cutting-edge research and the results of an experiment realized by a European research team, with the participation of the CMCC Foundation.

The recent accelerated loss of Arctic sea ice is partly due to an enhanced poleward Atlantic Ocean Heat Transport (OHT) due to both strengthening and warming of the oceanic inflow. Increasing the horizontal resolution of climate models improves their ability to represent the dynamics and complex interplay of processes at high latitudes that underlie climate change in the Arctic. This is in particular the main outcome of an innovative study realized by a European research team (among them, Dorotea Iovino and Alessio Bellucci, scientists of the CMCC Foundation – Euro-Mediterranean Center on Climate Change) that contribute to shed some light on the relations between the ocean, sea ice and climate at high-latitudes. The analysis, led by David Docquier (Earth and Life Institute, Université catholique de Louvain, Belgium), has been recently published on the prestigious journal Climate Dynamics, with the title: “Impact of model resolution on Arctic sea ice and North Atlantic Ocean heat transport“.

“In the framework of the EU Horizon 2020 PRIMAVERA project, the European ’brain’ of an international collaborative effort (HighResMIP, which is one of the CMIP6-endorsed Model Intercomparison Projects – MIPs)” Alessio Bellucci explains, “we have been able for the first time to systematically assess the impact of climate models’ resolution (i.e., their ability to represent processes with a better spatial definition) on a number of processes that are key for the Earth climate.”

This study, in particular, focuses on the Arctic and the complex interplay between sea ice (area, volume and thickness) and ocean circulation. “We know”, A. Bellucci says, “that the enhanced poleward Ocean Heat Transport (OHT) in the Atlantic is one of the main drivers for the sea-ice reduction recorded in the Arctic in the recent decades. Here, we investigated in detail the impact of model resolution on Arctic sea ice and Atlantic OHT by using five different state-of-the-art coupled Global Circulation Models (GCMs; among them, the CMCC model) that include dynamic representations of the ocean, atmosphere and sea ice and follow a commonly agreed experimental protocol. We underlined that, in particular, the processes studied are better represented with a finer ocean resolution, while the impact of atmosphere resolution is less clear.”

The results of the study clearly highlight how the area, volume and thickness of sea-ice decrease with the increase of the Atlantic OHT, especially north of 60∘N. The specific Arctic regions that are more directly influenced by Atlantic OHT are in the Atlantic sector of the Arctic Ocean, i.e. Barents/Kara Seas and Greenland-Iceland-Norwegian Seas, which first receive the warm Atlantic water inflow.

“The use of global climate models with an enhanced resolution in the ocean (25 km)” A. Bellucci concludes, “generally improves the representation of sea surface temperatures and ocean currents, leading to a better representation of climate variability in the Arctic region.

The CMCC contributed with its simulations and analyses to this important research on high-latitudes climate.”

This study uses the output of five high-resolution global climate models that follow the protocol of the High Resolution Model Intercomparison Project (HighResMIP) of the sixth phase of the Coupled Model Intercomparison Project (CMIP6) and participate in the EU Horizon 2020 PRIMAVERA project (PRocess-based climate sIMulation: AdVances in high-resolution modelling and European climate Risk Assessment). The overarching goal of PRIMAVERA is to develop a new generation of advanced and well-evaluated high-resolution global climate models, capable of simulating and predicting regional climate with unprecedented fidelity, for the benefit of governments, business and society in general.

Link to the article on Climate Dynamics:
https://link.springer.com/article/10.1007%2Fs00382-019-04840-y

Link to the page of the HighResMIP – High Resolution Model Intercomparison Project:
https://www.wcrp-climate.org/modelling-wgcm-mip-catalogue/cmip6-endorsed-mips-article/1068-modelling-cmip6-highresmip