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DC Flux

DC Flux Project Abstract:Lakes and reservoirs are shown to be important emitters of the greenhouse gas carbon dioxide (CO2). Understanding the processes that drive the movement of CO2 across the water - air interface is therefore important.  Recent eddie covariance studies (EC) that employ continuous monitoring of CO2 emissions from lakes and reservoirs indicate a diel cycle with increases in night-time CO2 fluxes that may be explained by enhanced transfer velocities due to in-water convection. Enhanced transfer velocities may occur on cloudless, calm nights when air temperatures drop rapidly. A large temperature gradient forms between the air and water body and the surface of the water cools rapidly. Turbulence in the water column occurs as cooling water at the surface sinks and is replaced by warmer underlying water. This turbulence circulates dissolved CO2 throughout the water column whilst smaller eddies close to the surface replenish CO2 at the water - air interface increasing gaseous flux to the atmosphere.Gaseous flux studies on lakes and reservoirs are mostly based on chamber measurements, however chambers are rarely deployed during the night-time. It is reasonable to speculate therefore that significant periods where potential high gas flux is occurring are not being measured leading to a bias in the estimation of total CO2 release from lakes and reservoirs to the atmosphere. Moreover, because the increase in night-time CO2 emission is controlled by the night-time temperature gradient between the water body and the air, presumably diel variation in emissions will also alter on a global scale, i.e. over a latitudinal gradient. This study therefore poses the following questions: Do we underestimate CO2 emissions from lakes by sampling only during the day?How do CO2 emissions vary between day and night over a latitudinal gradient? ProposalWe propose a year-long project to quantify and compare diel CO2 fluxes comprising four separate flux sampling events.The project intends to:·         Establish a global team of participating GLEON lakes for the project·         Organise / assist in the assembly and distribution of bespoke CO2 chambers to team members·         Establish protocols and standard operating procedures for deploying the chambers and analysing the data·         Quantify a day and a night-time flux of CO2 from each lake surface at four separate sampling times during the year·         Gather, organise and analyse the data with the aim of producing a paper for publication in a high-impact peer-reviewed journal 

Timeline: 
2016-07-07 to 2018-07-07

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