TY - JOUR

T1 - Energy input and dissipation in a temperate lake during the spring transition

AU - Woolway, Richard

AU - Simpson, John

PY - 2017/8

Y1 - 2017/8

N2 - ADCP and temperature chain measurements have been used to estimate the rate of energy input by wind stress to the water surface in the south basin of Windermere. The energy input from the atmosphere was found to increase markedly as the lake stratified in spring. The efficiency of energy transfer (Eff), defined as the ratio of the rate of working in near-surface waters (RW) to that above the lake surface (P10), increased from ~0.0013 in vertically homogenous conditions to ~0.0064 in the first 40 days of the stratified regime. A maximumvalue of Eff~0.01 was observed when, with increasing stratification, the first mode internal seiche period decreased to match the diurnal wind period of 24 h. The increase in energyinput, following the onset of stratification was reflected in enhancement of the mean depth varying kinetic energy without a corresponding increase in wind forcing. Parallel estimates ofenergy dissipation in the bottom boundary layer, based on determination of the Structure Function show that it accounts for ~15% of RW in stratified conditions. The evolution of stratification in the lake conforms to a heating stirring model which indicates that mixing accounts for ~21% of RW. Taken together, these estimates of key energetic parameters, pointthe way to the development of full energy budgets for lakes and shallow seas.

AB - ADCP and temperature chain measurements have been used to estimate the rate of energy input by wind stress to the water surface in the south basin of Windermere. The energy input from the atmosphere was found to increase markedly as the lake stratified in spring. The efficiency of energy transfer (Eff), defined as the ratio of the rate of working in near-surface waters (RW) to that above the lake surface (P10), increased from ~0.0013 in vertically homogenous conditions to ~0.0064 in the first 40 days of the stratified regime. A maximumvalue of Eff~0.01 was observed when, with increasing stratification, the first mode internal seiche period decreased to match the diurnal wind period of 24 h. The increase in energyinput, following the onset of stratification was reflected in enhancement of the mean depth varying kinetic energy without a corresponding increase in wind forcing. Parallel estimates ofenergy dissipation in the bottom boundary layer, based on determination of the Structure Function show that it accounts for ~15% of RW in stratified conditions. The evolution of stratification in the lake conforms to a heating stirring model which indicates that mixing accounts for ~21% of RW. Taken together, these estimates of key energetic parameters, pointthe way to the development of full energy budgets for lakes and shallow seas.

U2 - 10.1007/s10236-017-1072-1

DO - 10.1007/s10236-017-1072-1

M3 - Article

VL - 67

SP - 959

EP - 971

JO - Ocean Dynamics

JF - Ocean Dynamics

SN - 1616-7341

IS - 8

ER -