Pan-Eurasian Experiment (PEEX): Towards a holistic understanding of the feedbacks and interactions in the land-Atmosphere-ocean-society continuum in the northern Eurasian region

The northern Eurasian regions and Arctic Ocean will very likely undergo substantial changes during the next decades. The Arctic-boreal natural environments play a crucial role in the global climate via albedo change, carbon sources and sinks as well as atmospheric aerosol production from biogenic volatile organic compounds. Furthermore, it is expected that global trade activities, demographic movement, and use of natural resources will be increasing in the Arctic regions. There is a need for a novel research approach, which not only identifies and tackles the relevant multi-disciplinary research questions, but also is able to make a holistic system analysis of the expected feedbacks. In this paper, we introduce the research agenda of the Pan-Eurasian Experiment (PEEX), a multi-scale, multi-disciplinary and international program started in 2012 (https://www.atm.helsinki.fi/peex/). PEEX sets a research approach by which large-scale research topics are investigated from a system perspective and which aims to fill the key gaps in our understanding of the feedbacks and interactions between the land-Atmosphere-Aquatic-society continuum in the northern Eurasian region. We introduce here the state of the art for the key topics in the PEEX research agenda and present the future prospects of the research, which we see relevant in this context

Radiatively driven convection in an ice-covered lake investigated by using temperature microstructure technique

[1] Convection in an ice-covered lake, driven by the absorption of solar radiation, is investigated by means of temperature microstructure technique. This type of convection typically occurs in spring, when melting snow on the ice cover enables solar radiation to penetrate into the water body. The diurnal dynamics of the stratification system of five distinct layers is analyzed by means of consecutive CTD profiles and with the aid of a one-dimensional model. The model solves the transfer equation of heat and salinity and includes convective procedures to react on density instabilities. This study is focused on the turbulent kinetic energy (TKE) balance. The stratification analysis reveals the importance of several processes for the TKE balance, namely: (1) the entrainment into the top layer from the convective layer below, (2) the inflow of water from melted ice, and (3) the volumetric solar heating. Enabled by the analysis of the temperature microstructure profiles, two TKE budgets are presented. The temporally averaged budget reveals a vertical distribution of generation and dissipation rate similar to the case of cooling-induced convection in a surface boundary layer. But contrary to this reference regime, a transition layer was found in the upper convective layer, where both rates drop back to zero toward the layer above. The second TKE budget is spatially averaged over the convective layer but resolves the diurnal dynamics. The generation rate and dissipation rate feature similar diurnal dynamics, where the dissipation lags on average by 1.5 hours. The temporal change rate of TKE was found to be on the same order of magnitude as the generation rate and the dissipation rate, while the export rate of TKE out of the convective layer was found to be less significant