Sea Ice Deformation and Snow for an Arctic in Transition

SIDRiFT set the stage for a better understanding of the role of sea ice deformation and snow on ice in the changing Arctic climate. Arctic sea ice became thinner and more vulnerable to the impacts of winds and ocean currents. Sea ice is drifting faster and is pilled up in ridges or moved apart in leads more frequently. The amount and distribution of sea ice ridges, leads and snow have a large effect not only sea ice growth in the winter but also on the sea ice melt, extent and thickness in the summer. This means that winter sea ice and snow dynamics have a significant impact on climate and navigability that lasts beyond the winter season. Recent and ongoing satellite remote sensing data sets offer an opportunity to establish a better understanding of these processes on a detailed regional scale. In SIDRiFT we established a combination of satellite remote sensing, field observations and numerical model tools to study the interactions of snow and ice processes interlinked in sea ice deformation. We used mid-scale spatial resolution (40-100 m) of radars mounted on polar-orbiting satellites to detect sea ice deformation process and high resolution (approximately 5 m) to detect sea ice deformation consequences: occurrence of leads and pressure ridges. Rough surfaces such as ridges and lead edges capture large amounts of snow and leave the rest of the ice with correspondingly fewer snow. Because snow is an excellent thermal insulator surfaces with thinner snow will grow thicker ice through the winter. Such ice will be more resilient to melt in summer. In turn, the broken up ice in ridges and thin ice in leads will melt faster. Because snow on sea ice detection from satellite sensors is still under development, we used instead high resolution numerical models and field observations (e.g. from MOSAiC: https://mosaic-expedition.org/) to estimate the snow thickness on level and deformed ice. The most important results of SIDRiFT are: 1. Newly developed tools to use the satellite radar data to detect and characterize winter sea ice deformation with unprecedented spatial resolution 2. Detection of deformed ice and leads in the high resolution radar images based on back-scatter and texture of the ice surface. 3. Observational evidences of influence of sea ice roughness for snow accumulation and at the same time, the influence of snow accumulation on the sea ice growth. 4. Development of high resolution snow and sea ice numerical model with assimilation of observational data indicates the spatial heterogeneity and tight coupling of snow-ice processes. Our results will help to improve our understanding of the Earth climate system and help develop simplified (lower resolution) global climate models and Arctic weather prediction models. The sea ice deformation detection from mid-scale spatial resolution can also be used as an operational tool for sea ice navigation.

SIDRiFT resulted in 15 academic articles, of which 4 were lead by the project participants. Two more such academic articles are in writing and will be finalized after the project period. SIDRiFT will also contribute to a book chapter. This project was involved with several educational activities at the UiT The Arctic University of Norway. SIDRiFT disseminated the field science of MOSAiC expedition by educating future researchers by organizing a field day on the local fjord ice at Tromsø in 2021, 2022 and 2024. The activity is also planned for February 2024 and attempts are being made to make this a permanent activity for the UiT students in the coming years. The field day was also used a introductory activity for the university students that later participated in more extensive educational activities like scientific cruises and field schools. In spring 2021 SIDRiFT supported the Nansen Legacy expedition to the Northern Barents Sea. This were difficult times during COVID-19 restrictions and field personnel was hard to find. By participating in the cruise we enabled the transfer to the MOSAiC methods to the Norwegian research institutions. More about the Nansen Legacy project can be read here: https://arvenetternansen.com. In spring 2022 SIDRiFT assisted in organization of the Centre for Integrated Remote Sensing and Forecasting for Arctic Operations (CIRFA) cruise, where 9 young scientists were trained in Arctic field work relevant for radar remote sensing of sea ice and ice bergs. More about RCN Center of science and innovation CIRFA can be read here: cirfa.uit.no. In spring 2023 SIDRiFT co-organized an international and multidisciplinary field school along the Bottom-sea ice Respiration and nutrient Exchanges Assessed for THE Arctic (BREATHE) project, where 20 students (master and PhD) were trained. SIDRiFT prepared 3 classroom lectures, 5 days of field classes and 3 days of laboratory classes, all connected to sea ice. More about RCN project BREATHE can be read here: https://www.breathearctic.com/ In spring 2024 SIDRiFT legacy will be used at a Marine biology course of UNIS at the Svea research station in Van Mijenfjorden, Svalbard with master 20 students. The backtrajectory code developed at SIDRiFT is in operational use by the Norwegian Polar Institute (NPI) and it will be improved in collaboration with the ongoing Sustainable Development of the Arctic Ocean (SUDARCO) project – a Fram Center project lead by the NPI. The code is publicly available at: https://github.com/loniitkina/sidrift. More about SUDARCO can be found here: https://www.npolar.no/en/fact/sudarco/. We are currently searching for resources to integrate the sea ice deformation code published by Itkin [2024] into the NPI navigational tool for ice breaker navigation. The current state of the code is publicly available at: https://github.com/loniitkina/sid

Arctic sea ice internal strength is reduced due to its general thinning. Simultaneously, the wind forcing of winter storms has increased due to their greater frequency. As a consequence ice drift speed has increased and evidences from buoy data show an increase in sea ice deformation. Satellite remote sensing datasets offer an opportunity to establish a better understanding of these processes on a detailed regional scale. In SIDRiFT we will combine the historic and new Synthetic Aperture Radar (SAR) satellite data (including Sentinel-1,A,B of European Space Agency) to estimate the increase in the sea ice deformation, occurrence of leads and deformed ice fraction. Indirectly, increased deformation alters the accumulation of snow cover on rough surface compared to level sea ice and consequently the heat fluxes through it. Snow on sea ice detection methods from space are still under development and to fill this knowledge-gap, we will use high resolution numerical models. Current Earth System Models (ESMs) are not able to capture the recent trends in Arctic sea ice decline or represent the snow cover accurately. The spatial scales of sea ice deformation features and snow inhomogeneity are both below ESMs resolution are one of the heat transfer mechanisms that are inadequately represented in ESMs. To account for this problem SIDRiFT will provide regional scale SAR validation datasets and high resolution snow depth and sea ice thickness model output. Both are highly sought after by model developers and teams developing satellite and air-borne remote sensing of snow. Furthermore, improving the numerical models (climate and forecasting) and remote sensing of environment will support the knowledge-based management that Norway as well as international decision-makers are striving for.