The Atlantic Gateway to the Arctic: St Petersburg University researchers study the causes of climate change in the Arctic and Subarctic regions

"The Atlantic Gateway to the Arctic: Ocean Circulation as a Factor of Long-Term Arctic Climate Variability and the State of Polar Ecosystems" is a comprehensive, interdisciplinary study of the ocean—atmosphere interactions in marine ecosystems. The first stage of the research was completed in 2021. The main research objective is to clarify the ocean’s role in climate change in the Arctic and the impact of climate change on the current state of ecosystems in the Arctic region, which is particularly important for Russia. The collaboration of experts in oceanography, atmospheric dynamics and primary productivity of marine ecosystems has enabled to cover a wide range of conceptual and practical problems associated with rapid warming of the Arctic region. The study covers the area of the Northern Europe’s sea basins (the Greenland Sea, the Norwegian Sea and the Barents Sea) and the neighbouring regions of the Eurasian sector of the Arctic.

Here are the facts: Arctic air temperatures are rising about twice as fast as in tropical and temperate latitudes; the Arctic sea ice is decreasing dramatically; the ocean water temperatures are increasing; and the fresh water balance of the Arctic Ocean is changing.

Igor Bashmachnikov, Principal Investigator of the project, Candidate of Geography, Associate Professor in the Department of Oceanology at St Petersburg University

‘Accelerated climate change in the Arctic is associated with the specific expression of functioning of the feedback mechanisms in the Arctic climate system. The negative feedback mechanisms that stabilise the climate system are weakened here. In contrast, the positive feedback mechanisms that accelerate the climate change and destabilise the climate system are more effective in polar regions than at low latitudes. Furthermore, for the climate change feedback mechanisms to work, strong external influences are required to start the self-regulating processes in the Arctic. In the current project, we focus on one of the possible trigger factors leading to further deregulation of the Arctic climate system — the variability of oceanic heat fluxes to the Arctic,’ explained Igor Bashmachnikov, Candidate of Geography, Associate Professor in the Department of Oceanology at St Petersburg University.

Findings from the first stage of the project show that the ocean—atmosphere heat fluxes in the Arctic contribute to heat transport fluctuations in both media on time scales of 10-15 years. An increase in the poleward heat transport in the ocean leads to a general decrease in the atmosphere heat transport to the polar regions after about three years, resulting in further decline of the ocean heat transport. This is the so-called Bjerknes compensation of heat transport variations. Since the 1980s, however, due to the increase in the mean global temperature, this mechanism has begun to malfunction. In the Arctic, this is most clearly seen in the Barents Sea.

The project findings have revealed that an increase in ocean heat transport changes the spatial distribution of the wind speed and wind direction over the Barents Sea in such a way that it leads not to a decline, but to a further increase in both atmosphere and ocean poleward heat transport. Consequently, in recent decades, the air temperatures over the Barents Sea have been rising twice as fast as in the rest of the Arctic.

Igor Bashmachnikov, Principal Investigator of the project, Candidate of Geography, Associate Professor in the Department of Oceanology at St Petersburg University

According to Igor Bashmachnikov, it is the advancements in basic science that enable improving the climate models used to predict the future climate of the Arctic and other regions of Russia. At present, modelling results indicate that due to the ongoing climate change the development of promising hydrocarbon deposits and other mineral resources on the Arctic shelf may become more accessible. With the rapid decline of Arctic sea ice extent and thickness, the strategic importance of the Northern Sea Route increases. On this account, an accelerated modernisation of a number of Russian Arctic Sea ports is being carried out.

‘Nevertheless, a wide variation in model estimates of the ice melting intensity in the Arctic and other climatic parameters contributes to the uncertainty in Arctic climate change projections. Our project aims to assess ocean heat transport into the Arctic as an essential component of the climate system, and our research is key to monitoring the physical and hydrological processes of the Arctic region,’ Igor Bashmachnikov emphasised.

Igor Bashmachnikov stressed that the project outcomes are instrumental in achieving a better understanding of the key role of the subpolar North Atlantic in the climate system of the Arctic. The project findings will improve the reliability of the climate change projections, thus contributing to the leadership of the Russian Federation in the scientific development of the Arctic region.

‘The largest contributor of oceanic heat to the Arctic Ocean is the warm Atlantic water. The system of ocean currents that transport warm, upper Atlantic waters from the tropics to subpolar and polar latitudes is called the upper branch of the Atlantic Meridional Overturning Circulation (AMOC). At high latitudes, the ocean heat is released into the atmosphere, with a significant part of the atmospheric heat being then transferred to the Arctic. The cooled oceanic waters sink to a depth of 1,000–3,000 metres in the process of deep ocean convection and feed a return flow from the Arctic to the tropics. As the regions of overturning of surface and deep ocean water flows, the convection zones are controlling mechanisms of the AMOC. As part of the second stage of the project, new convection indices have been obtained, which enables to identify the variability in the deep convection intensity in the main sites of deep convection (the Greenland Sea, the Labrador Sea, and the Irminger Sea) over the past 70 years. In particular, it has been revealed that it is the convective activity in the Irminger Sea that plays the key role in the AMOC variability. Previously, the Labrador Sea Deep Convection Area was considered the main controlling mechanism of the AMOC strength and stability. Currently, the negative feedback mechanism of the AMOC — the Irminger Sea — is being studied, which may explain the rather high stability of the AMOC in recent decades,’ said Igor Bashmachnikov.

The project will also explore the impact of ocean heat transport on high-latitude marine ecosystems. For this, satellite data on phytoplankton dynamics and data collected through field observations are being studied, including the findings from the last expedition of the project participants to the Barents Sea in 2021.

For reference, according to the Decree of the President of the Russian Federation "On the Strategy for Scientific and Technological Development of the Russian Federation" dated 1 December 2016, the scientific and technological development of the Russian Federation is one of the priorities of state policy. Strengthening Russia’s position in the field of Arctic exploration is a key to the development of Russia that ensures the capabilities of the country to meet the challenges of our time.

As part of the project "The Atlantic Gateway to the Arctic: Ocean Circulation as a Factor of Long-Term Arctic Climate Variability and the State of Polar Ecosystems", the cloud storage of the Computing Centre of St Petersburg University has been used. Additionally, the expedition to the Barents Sea used the equipment of the Resource Centre "Environmental Safety Observatory".