Flying Through Storms To Understand Their Interaction with Sea Ice: The Arctic Summer-time Cyclones Project and Field Campaign

By: Ambrogio Volonté

Arctic cyclones are the leading type of severe weather system affecting the Arctic Ocean and surrounding land in the summer. They can have serious impacts on sea-ice movement, sometimes resulting in ‘Very Rapid Ice Loss Events’, which present a substantial challenge to forecasts of the Arctic environment from days out to a season ahead. Summer sea ice is becoming thinner and more fractured across widespread regions of the Arctic Ocean, due to global warming. As a result, winds can move the ice around more easily. In turn, the uneven surface can exert substantial friction on the atmosphere right above it, impacting the development of weather systems. Thus, a detailed understanding of the two-way relationship between sea ice and Arctic cyclones is crucial to allow weather centres to provide reliable forecasts for the area, an increasingly important issue as the Arctic sees growing human activity.

This is the main goal of the Arctic Summer-time Cyclones project, led by Prof John Methven and funded by the UK Natural Environment Research Council (NERC). To this end, we designed a field campaign aiming to fly into Arctic cyclones developing over the marginal ice zone (that is the transitional area between pack ice and open ocean, where the ice is thinner and fractured, and where leads and melt ponds can be present). The campaign was based in Svalbard (Norwegian Arctic) and took place in July and August 2022, one year later than originally planned due to the Covid pandemic. The field campaign team included scientists from the University of Reading (John Methven, Suzanne Gray, Ben Harvey, Oscar Martinèz-Alvarado, Ambrogio Volonté and Hannah Croad), the University of East Anglia (UEA), and the British Antarctic Survey (BAS). We were joined by researchers from the US and France, funded by the Office of Naval Research (USA).

Figure 1: Some components of the Arctic Summer-time Cyclones field campaign team in front of the Twin Otter aircraft. Photo by Dan Beeden (BAS).

Using the BAS MASIN Twin Otter aircraft, we performed 15 research flights during the campaign, targeting four Arctic cyclones and several other weather features associated with high winds near the surface. Flying at very low levels (even below 100ft when allowed by visibility conditions and safety standards) we were able to detect the turbulent fluxes of heat and momentum characterising the interaction between surface and atmosphere. Vertical profiles and stacks of horizontal legs at different heights were used to sample for the first time the 3D structure of wind jets present in the first km above the surface in Arctic summer cyclones. Our partners from France and US also completed a similar number of flights using their SAFIRE ATR42 aircraft. Although their activities were mainly focused on cloud structure and mixed phase (ice-water) processes higher up, some coordinated flights were carried out, with both aircrafts flying in the same area to maximise data collection. For more details on our campaign activities (plus photos and videos from the Twin Otter!) see the ArcticCyclones Twitter account and the blogs on our project website.

Figure 2: An example of sea ice as seen from the cockpit of the Twin Otter during the flight on 30 July 2022. Photo by Ian Renfrew (UEA).

Now that the field campaign has concluded, data analysis is proceeding apace. Flight observations are being compared against model data from operational weather forecasts and dedicated high-resolution simulations. While our colleagues at the University of East Anglia are analysing the observed turbulent fluxes over sea ice to improve their representation in forecast models, here at Reading we are looking at the detailed 3D structure of Arctic cyclones and at the processes driving their lifecycle. Preliminary results highlight the sharpness of the low-level wind jet present in their cold sector, with observations suggesting that jet cores are stronger and shallower than shown by current models. However, more detailed analysis is still needed to confirm these results. At the same time, novel analysis methods are being implemented on experimental model data, taking advantage of the properties of conservation and inversion of atmospheric variables such as potential vorticity and potential temperature. The aim is to isolate the contributions of individual processes, such as friction and heating, to the dynamics of the cyclone and thus highlight the effects of atmospheric-surface interaction on cyclone development.

Figure 3: Example of flight planner map (software developed by Ben Harvey, Reading) used to set up the flight route of one of the campaign flights. Background data from UK Met Office (Crown copyright).

While we are surely missing the sense of adventure of our Arctic field campaign, the excitement for the scientific challenge is still accompanying us as we analyse the data here in Reading and collaborate with our UK and international partners. Stay tuned if you are interested in how Arctic cyclones work, how they interact with the changing sea ice and how Arctic weather forecast can be improved. Results might soon be coming your way!


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