A thin gash in the continental slope northwest of Monterey Bay, Ascension Canyon, is steep, with sides and axis both strongly supercritical to M2 internal tides. A hydrostatic model forced with eight tidal constituents shows no major sources feeding energy into the canyon, but significant energy is exchanged between barotropic and baroclinic flows along the tops of the sides, where slopes are critical. Average turbulent dissipation rates observed near spring tide during April are half as large as a two week average measured during August in Monterey Canyon. Owing to Ascension's weaker stratification, however, its average diapycnal diffusivity, 3.9 × 10-3 m2 s-1, exceeded the 2.5 × 10-3 m2 s-1 found in Monterey. Most of the dissipation occurred near the bottom, apparently associated with an internal bore, and just below the rim, where sustained cross-canyon flow may have been generating lee waves or rotors. The near-bottom mixing decreased sharply around Ascension's one bend, as did vertically integrated baroclinic energy fluxes. Dissipation had a minor effect on energetics, which were controlled by flux divergences and convergences and temporal changes in energy density. In Ascension, the observed dissipation rate near spring tide was 2.1 times that predicted from a simulation using eight tidal constituents averaged over a fortnightly period. The same observation was 1.5 times the average of an M2-only prediction. In Monterey, the previous observed average was 4.9 times the average of an M2-only prediction

[1] A dye study was conducted to track an intrusion generated at the boundary of a small lake. Persistent turbid layers offshore presented evidence of possible intrusions from boundary mixing. After high winds, a streak of Rhodamine WT was injected at the boundary of the lake where the slope was between 5% and 10%. Both vertical profiles and longitudinal transects of the dye concentration were measured. The three-dimensional dye mapping showed a distinct dye intrusion, ranging between 0.5 and 1 m thick, over 200 m in horizontal extent offshore, 1 day after the injection. Profiles of temperature microstructure measured soon after the injection both at the injection site and offshore showed an elevated eddy diffusivity near the boundary where the dye was injected, indicating that the intrusion resulted from boundary mixing. Because the dominant internal waves are subcritical, the mixing is most likely due to seiching currents interacting with the boundary. The propagation characteristics of the intrusion were predicted most closely by a formulation for a radially spreading intrusion governed by a balance between buoyancy and inertia. These results show that intrusion generation and propagation may be a significant process for mass transport in stratified lakes and reservoirs.Citation: Wain, D. J., and C. R. Rehmann (2010), Transport by an intrusion generated by boundary mixing in a lake, Water Resour. Res., 46, W08517,

Abstract. Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a single model forced with limited scenario-driven projections of future climate for a relatively small number of lakes. As a result, our understanding of the effects of climate change on lakes is fragmentary, based on scattered studies using different data sources and modelling protocols, and mainly focused on individual lakes or lake regions. This has precluded identification of the main impacts of climate change on lakes at global and regional scales and has likely contributed to the lack of lake water quality considerations in policy-relevant documents, such as the Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC). Here, we describe a simulation protocol developed by the Lake Sector of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) for simulating climate change impacts on lakes using an ensemble of lake models and climate change scenarios for ISIMIP phases 2 and 3. The protocol prescribes lake simulations driven by climate forcing from gridded observations and different Earth system models under various representative greenhouse gas concentration pathways (RCPs), all consistently bias-corrected on a 0.5∘ × 0.5∘ global grid. In ISIMIP phase 2, 11 lake models were forced with these data to project the thermal structure of 62 well-studied lakes where data were available for calibration under historical conditions, and using uncalibrated models for 17 500 lakes defined for all global grid cells containing lakes. In ISIMIP phase 3, this approach was expanded to consider more lakes, more models, and more processes. The ISIMIP Lake Sector is the largest international effort to project future water temperature, thermal structure, and ice phenology of lakes at local and global scales and paves the way for future simulations of the impacts of climate change on water quality and biogeochemistry in lakes.

Abstract. Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a single model forced with limited scenario-driven projections of future climate for a relatively small number of lakes. As a result, our understanding of the effects of climate change on lakes is fragmentary, based on scattered studies using different data sources and modelling protocols, and mainly focused on individual lakes or lake regions. This has precluded identification of the main impacts of climate change on lakes at global and regional scales and has likely contributed to the lack of lake water quality considerations in policy-relevant documents, such as the Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC). Here, we describe a simulation protocol developed by the Lake Sector of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) for simulating climate change impacts on lakes using an ensemble of lake models and climate change scenarios. The protocol prescribes lake simulations driven by climate forcing from gridded observations and different Earth system models under various Representative Greenhouse Gas Concentration Pathways, all consistently bias-corrected on a 0.5° × 0.5° global grid. In ISIMIP phase 2, 11 lake models were forced with these data to project the thermal structure of 62 well-studied lakes where data were available for calibration under historical conditions, and for nearly 17,500 lakes using uncalibrated models and forcing data from the global grid where lakes are present. In ISIMIP phase 3, this approach was expanded to consider more lakes, more models, and more processes. The ISIMIP Lake Sector is the largest international effort to project future water temperature, thermal structure, and ice phenology of lakes at local and global scales and paves the way for future simulations of the impacts of climate change on water quality and biogeochemistry in lakes.