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Effects of Wind and Buoyancy on Carbon Dioxide Distribution and Air‐Water Flux of a Stratified Temperate Lake
Author(s) -
Czikowsky Matthew J.,
MacIntyre Sally,
Tedford Edmund W.,
Vidal Javier,
Miller Scott D.
Publication year - 2018
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2017jg004209
Subject(s) - diel vertical migration , environmental science , carbon dioxide , stratification (seeds) , atmospheric sciences , daytime , downwelling , water column , flux (metallurgy) , hypolimnion , oceanography , upwelling , geology , chemistry , eutrophication , seed dormancy , germination , botany , organic chemistry , dormancy , biology , nutrient
Improved calculations of emissions of greenhouse gases from stratified lakes require understanding the physical processes controlling transport of dissolved gases to the air‐water interface on diel, synoptic, and seasonal time scales. We address this issue during the transition from late summer to autumn cooling in a small temperate lake by combining micrometeorology, physical limnology, and carbon dioxide (CO 2 ) measurements throughout the water column. Over the 26‐day campaign, the lake cooled and emitted CO 2 with daily average loss of 23 mmol CO 2 m −2 d −1 . Over diel cycles, lake surface pCO 2 decreased during daytime heating and increased during nighttime cooling, while daytime CO 2 fluxes exceeded nighttime fluxes by 35% due to higher daytime wind speeds. We compared the effects of diel and synoptic weather patterns on the CO 2 distribution within the lake and lake‐atmosphere CO 2 flux. Increases in near‐surface pCO 2 scaled with stratification and heat loss which moderated transport of dissolved gases into the mixed layer. When winds were above ~4 m s −1 , lake‐scale circulations drove upwelling and downwelling that redistributed heat and carbon dioxide between the northeast and southwest basins. Short‐burst peak CO 2 fluxes exceeded 50 mmol m −2 d −1 during windy periods associated with storms. However, the seasonal cooling‐induced transition to persistent deep mixing led to the highest CO 2 concentrations in the mixed layer and at the surface and the highest sustained CO 2 fluxes (approaching 100 mmol m −2 d −1 ).