Glider observations of radiatively driven convection

Session: Physical Processes in Lakes (2)

Jay Austin, Large Lakes Observatory, UMD, [email protected]

Abstract

Improved analysis of autonomous glider data during has provided new insight into Radiatively Driven Convection. A more careful consideration of both the temperature field and the chl-a fluorescence field reveal the fine structure of individual convective cells. An analysis of a 5 day glider deployment in June 2013 reveal 75 anomalous regions which appear in both the temperature and fluorescence fields, suggesting the presence of water that has recently been exposed to bright sunlight.  Previously considered moored data and a lack of coherence from one profile to the next suggest that these anomalous regions are actually vertical chimneys of rapidly downwelling water, rather than horizontal layers or localized boluses of water. The horizontal scales of the individual chimneys are on the order of 10’s of meters, and an abundance analysis of the regions suggests that the horizontal scales of the convective cells themselves is on the order of 50m. The character of the anomalous regions changes with depth, suggesting that the nature of the convective process is different above and below 100m. This is consistent with previous analysis of temperature data from moorings.