Publikationsdatum:
2015-07-22
Beschreibung:
To understand the carbon and energy exchange between the lake surface and the atmosphere, direct measurements of latent, sensible heat and CO 2 fluxes were taken using the eddy covariance (EC) technique in western Lake Erie during October 2011-September 2013. We found that the latent heat flux ( LE ) had a marked one-peak seasonal change in both years that differed from the diurnal course and lacked a sinusoidal dynamic common in terrestrial ecosystems. Daily mean LE was 4.8±0.1 and 4.3±0.2 MJ m -2 d -1 in Year 1 and Year 2, respectively. The sensible heat flux ( H ) remained much lower than the LE , with a daily mean of 0.9±0.1 and 1.1±0.1 MJ m -2 d -1 in Year 1 and Year 2, respectively. As a result, the Bowen ratio was 〈1 during most of the two-year period, with the lowest summer value at 0.14. The vapor pressure deficit explained 35% of the variation in half-hourly LE , while the temperature difference between the water surface and air explained 65% of the variation in half-hourly H . Western Lake Erie acted as a small carbon sink holding -19.0±5.4 and -40.2±13.3 g C m -2 in the first and second summers (May-September) but as an annual source of 77.7±18.6 and 49.5±17.9 g C m -2 yr -1 in Year 1 and Year 2, respectively. The CO 2 flux ( ) rate varied from -0.45 g C m -2 d -1 to 0.98 g C m -2 d -1 . Similar to LE , had noticeable diurnal changes during the months that had high chlorophyll a months, but not during other months. A significantly negative correlation ( P 〈0.05) was found between and chlorophyll a on monthly fluxes. Three gap-filling methods, including marginal distribution sampling (MDS), mean diurnal variation (MDV) and monthly mean, were quantitatively assessed, yielding an uncertainty of 4%, 6% and 10% in LE , H and , respectively.
Print ISSN:
0148-0227
Thema:
Biologie
,
Geologie und Paläontologie
Permalink