We investigated radiatively driven under-ice convection in Lake Onego (Russia) during 3 consecutive late winters. In ice-covered lakes, where the temperature of water is below the temperature of maximum density, radiatively driven heating in the upper water column induces unstable density distributions leading to gravitational convection. In this work, we quantified the key parameters to characterise the radiatively driven under-ice convection: (1) the effective buoyancy flux, B * (driver), and its vertical distribution; (2) the convective mixed-layer thickness, h CML (depth scale); and (3) the convective velocity, w * (kinematic scale). We compared analytical w * scaling estimates to in situ observations from high-resolution acoustic Doppler current profilers. The results show a robust correlation between w * and the direct observations, except during the onset and decay of the solar radiation. Our results highlight the importance of accurately defining the upper limit of h CML in highly turbid water and the need for spectrally resolving solar radiation measurements and their attenuation for accurate B * estimates. Uncertainties in the different parameters were also investigated. We finally examined the implications of under-ice convection for the growth rate of nonmotile phytoplankton and provide a simple heuristic model as a function of easily measurable parameters.

BackgroundMental illness is a major public health concern. Despite progress understanding which treatments work, a significant treatment gap remains. An ongoing concern is treatment length. Modular, flexible, transdiagnostic approaches have been offered as one solution to scalability challenges. The Common Elements Treatment Approach (CETA) is one such approach and offers the ability to treat a wide range of common mental health problems. CETA is supported by two randomized trials from low- and middle-income countries showing strong effectiveness and implementation outcomes.Methods/designThis trial evaluates the effectiveness and implementation of two versions of CETA using a non-inferiority design to test two primary hypotheses: (1) a brief five-session version of CETA (Brief CETA) will provide similar effectiveness for reducing the severity of common mental health problems such as depression, post-traumatic stress, impaired functioning, anxiety, and substance use problems compared with the standard 8–12-session version of CETA (Standard CETA); and (2) both Brief and Standard CETA will have superior impact on the outcomes compared to a wait-list control condition. For both hypotheses, the main effect will be assessed using longitudinal data and mixed-effects regression models over a 6-month period post baseline. A secondary aim includes exploration of implementation factors. Additional planned analyses will include exploration of: moderators of treatment impact by disorder severity and comorbidity; the impact of individual therapeutic components; and trends in symptom change between end of treatment and 6-month assessment for all participants.DiscussionThis trial is the first rigorous study comparing a standard-length (8–12 sessions) modular, flexible, transdiagnostic, cognitive-behavioral approach to a shortened version of the approach (five sessions). Brief CETA entails “front-loading” with elements that research suggests are strong mechanisms of change. The study design will allow us to draw conclusions about the effects of both Brief and Standard CETA as well as which elements are integral to their mechanisms of action, informing future implementation and fidelity efforts. The results from this trial will inform future dissemination, implementation and scale-up of CETA in Ukraine and contribute to our understanding of the effects of modular, flexible, transdiagnostic approaches in similar contexts.Trial registrationClinicalTrials.gov, ID: NCT03058302 (U.S. National Library of Medicine). Registered on 20 February 2017.Electronic supplementary materialThe online version of this article (10.1186/s13063-018-2752-y) contains supplementary material, which is available to authorized users.

Fine scale structure of convective mixed layer in ice-covered lakes 3 tion without mean shear. The inertial subrange, covering order of magnitude in the spatial domain, was identified by fitting the 2 / 3 scaling power law to the structure function method, thus confirming the regime of fully developed turbulence. The calculated rate of dissipation of turbulent kinetic energy ε reaches values up to 3 × 10 −9 m 2 s −3. Although a strong correlation between ε and B was observed, ε picks up about 1 h later after the onset of the heating-phase. This delay roughly corresponds to the turnover time of the energy containing eddies. We finally observed a decay of ε at night, during the relaxation-phase, but, interestingly, the level remained above the statistical error.

Oxygen conditions in ice-covered lakes depend on many factors, which, in turn, are influenced by a changing climate, so detection of the oxygen trend becomes difficult. Our research was based on data of long-term measurements of dissolved oxygen (2007–2020), water temperature, under-ice solar radiation, and snow-ice thickness (1995–2020) in Lake Vendyurskoe (Northwestern Russia). Changes of air temperature and precipitation in the study region during 1994–2020 and ice phenology of Lake Vendyurskoe for the same period based on field data and FLake model calculations were analyzed. The interannual variability of ice-on and ice-off dates covered wide time intervals (5 and 3 weeks, respectively), but no significant trends were revealed. In years with early ice-on, oxygen content decreased by more than 50% by the end of winter. In years with late ice-on and intermediate ice-off, the oxygen decrease was less than 40%. A significant negative trend was revealed for snow-ice cover thickness in spring. A climatic decrease of snow-ice cover thickness contributes to the rise of under-ice irradiance and earlier onset of under-ice convection. In years with early and long convection, an increase in oxygen content by 10–15% was observed at the end of the ice-covered period, presumably due to photosynthesis of phytoplankton.