Interdisciplinary results of MOSAiC drift published

Hundreds of international researchers are currently analyzing observations from the one-year MOSAiC expedition, during which hundreds of environmental parameters were recorded with unprecedented accuracy and frequency over a full annual cycle in the Central Arctic Ocean. Recently published articles present the first complete picture of the climate processes in the central Arctic.

Diminishing sea ice is a symbol of ongoing global warming: in the Arctic, its extent has almost halved in summer since satellite records began in the 1980s. Less well studied but equally relevant are the thickness and other properties of the ice. The question of what this means for the future Arctic and how these changes will affect the global climate were the impetus for the historic MOSAiC expedition with the German research icebreaker Polarstern from September 2019 to October 2020.

With the results coming out now the researchers are building the most complete observation-based picture of climate processes in the Arctic, where the surface air temperature has been rising more than two times as fast as on the rest of the planet since the 1970s. To study the relevant processes for a full year required a special concept, in part because the Central Arctic Ocean is still ice-covered in winter and therefore difficult to access.

During the expedition, the icebreaker froze to a large ice floe and drifted with the natural transpolar drift across the Arctic Ocean. And this is where the first surprises came.

"We found more dynamic and faster drifting pack ice than expected. This not only challenged the teams on the ground in their daily work, but above all resulted in changed sea-ice properties and sea-ice thickness distributions," reports Dr Marcel Nicolaus, sea-ice physicist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and co-leader of Team Ice in the MOSAiC project.

Sea-ice albedo was measured on ice and from air

Finnish Meteorological Institute (FMI) contributed to the MOSAiC sea ice and snow research in several ways. Firstly, FMI deployed a radar system on-board the Polarstern to measure sea ice motion and several automatic buoys to measure sea ice thickness, drift and pressure to examine seasonal changes in sea ice thermodynamics and dynamics. The measurements have revealed that the Arctic ice pack is very dynamic and fracturing even in the mid-winter when the sea ice is thick and cold period prevails.

Another major FMI’s contribution to the MOSAiC is related on the sea ice melting on summer. When sea-ice shrinks, its surface reflectivity called albedo decreases. Albedo tells how big fraction of solar energy is absorbed by the sea-ice and ocean or reflected to the space. As such, it is a key quantity to understand the ongoing Arctic climate change and its feedback mechanisms.

Sea-ice albedo is what researchers Roberta Pirazzini and Henna-Reetta Hannula from FMI went to measure. They used both instruments installed on the sea-ice, which run from the beginning until the end of the MOSAiC experiment, and instruments on drones.

“These measurements will enable the derivation of relationships between the albedo measured from ground-based platforms, which typically have metre-to-tens-of-meters footprint, and satellite observations or large-grid model outputs”, researcher Roberta Pirazzini explains.

The data will be used also to study the relation between sea-ice microphysical properties and albedo, and between biochemical and biological activity inside and below ice and surface energy budget.

The sea-ice albedo is an essential variable also for the study of the atmospheric processes occurring near the surface. Therefore, the FMI albedo observations from the fix station were done in close collaboration with the atmospheric team and will be compared with similar observations carried out on different types of surfaces (young ice, old ice, melt ponds, leads).

Roberta Pirazzini and Henna-Reetta Hannula participated to MOSAiC leg 5 through the project “DEvelopment of snow/ice/ecosystem models using winter-to-summer ARctic observations of coupled snow, ice, and ecosystem processes” (DEARice) funded by the EU H2020 project ARICE, with the contribution of the EU H2020 project INTAROS in the development of the drone SPECTRA.

Buoys provided information for remote sensing validation

During the first leg of the expedition, nine SIMBA snow and ice mass balance buoys of the Finnish Meteorological Institute were deployed in the vicinity of the MOSAiC ice camp. Buoys observed the spatial and temporal variability of snow and sea ice mass balance.

Measurements were made together with seven more SIMBA buoys from the Polar Research Institute of China (PRIC).

“The results of SIMBAs observations reveal large spatial variabilities of snow depth and sea ice thickness distributions. These served as ground truths for remote sensing validation and a better understanding of thermal regimes of snow and sea ice as well as air-sea ice-ocean interactions,” says researcher Bin Cheng from the Finnish Meteorological Institute.

The observations helped to conclude that the highly variable snow cover needs to be considered in the Arctic sea ice modelling.

Further information:

Research Professor Jari Haapala, Finnish Meteorological Institute, tel. +358 40 757 36 21, jari.haapala@fmi.fi

Senior Researcher Roberta Pirazzini, Finnish Meteorological Institute, tel. +358 50 358 2653, roberta.pirazzini@fmi.fi

Researcher Henna-Reetta Hannula, Finnish Meteorological Institute, tel. +358 40 670 7112, henna-reetta.hannula@fmi.fi

Senior Researcher Bing Cheng, Finnish Meteorological Institute, tel. +29 539 6427, bing.cheng@fmi.fi

Scientific articles:

All scientific articles are available on Elementa science journal.

ICE: Nicolaus, M, Perovich, DK, Spreen, G, Granskog, MA et al., 2022: Overview of the MOSAiC expedition: Snow and sea ice. Elementa: Science of the Anthropocene 10(1). DOI: https://doi.org/10.1525/elementa.2021.000046

OCEAN: Rabe, B, Heuzé, C, Regnery et al., 2022: Overview of the MOSAiC expedition – Atmosphere. Elementa, Science of the Anthropocene, 10 (1), DOI: https://doi.org/110.1525/elementa.2021.00060

ATMOS: Shupe, M.D., M. Rex, B. Blomquist, P.O.G. Persson, J. Schmale, T. Uttal et al., 2022: Overview of the MOSAiC expedition: Physical oceanography. Elementa: Science of the Anthropocene 10(1). DOI: https://doi.org/10.1525/elementa.2021.00062

Background information on MOSAiC

During the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, experts from 20 nations explored the Arctic for an entire year. From autumn 2019 to autumn 2020, the German research icebreaker Polarstern drifted frozen in the ice through the Arctic Ocean.

MOSAiC was coordinated by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). In order to make this unique project a success and to obtain the most valuable data possible, more than 80 institutes had pooled their resources in a research consortium. The total cost of the expedition was about 150 million euros, mostly funded by the German Federal Ministry of Education and Research.

Website: MOSAiC expedition