What happens as the surface of the Arctic sea ice begins to melt? What are the most important processes at play? And is the timing of the melt tied in with intrusions of warm and moist air from the mid-latitudes? Those are some of the questions that will be addressed by the ARTofMELT (Atmospheric rivers and the onset of Arctic melt) expedition on the Swedish research icebreaker Oden in spring, departing from Longyearbyen on 7 May and returning on 15 June, 2023. With support from IASC, ARTofMELT held a workshop at Stockholm University 11-13 October, 2022, attended by about ~40 participants in person with a handful on line. The workshop started with a half-day open science symposium in collaboration with the Bolin Centre of Climate Research (BCCR), then went through all the suggested work packages, suggested science targets and logistical needs, and ended with breakout groups laying the foundation for the logistical planning. The workshop was a great success, and was in addition to IASC also supported by the International Meteorological Institute (IMI), the BCCR and the Swedish Polar Research Secretariat (SPRS). IASC travel funding made it possible to invite 5 Early Career Scientists, three from the US, one from UK and one from Germany, that will now participate in the expedition.
Understanding and being able to correctly model the onset of the melt is important for forecasting on scales from months and seasons to decades. ARTofMELT is intending to provide observations to facilitate the understanding that will be the scientific underpinning for improved climate and weather-forecast models. Two things are unusual with ARTofMELT; the timing and the navigation strategy. Icebreaker expeditions into the Arctic Ocean most often happens in late summer or early autumn, simply because there is less sea ice and the ice is also easier to break. As a consequence, there is much more observations of the fall transition than of its spring counterpart. But with the target to study the annual spring transition, from a frozen to a melting Arctic, it follows one has to be there when this happens – in spring! Atmospheric river is a nick-name for filaments of warm and often moist air entering into the Arctic from farther south, and are driven by weather systems. Limited extent and the sporadic nature make it more or less luck to observe one with an expedition that is either stationary or follows a preplanned route. Therefore, we instead plan to use so-called ensemble weather forecasts at a lead times of 5-7 days, to give us information on where and when atmospheric rivers are expected. Then we will simply move the Oden to the indicated position and wait. Rather than relying on one single forecast, ensemble forecasting summarize output from a large number of similar weather forecasts, all with slightly different initial conditions sampling observation and model uncertainty.
- This strategy also means that deploying instruments on the ice must be in a mobile fashion, so that instruments that can be quickly retrieved, and most observations will be carried out from onboard or from airborne sensors.
- We intend to take observations in a column extending from the upper ocean, through the ice and up through the atmosphere, with an emphasis on the lowest kilometer, using both in-situ and remote sensing instruments.
- The focus for these observations will be on the processes responsible for energy fluxes between the three systems.