LEXPLORE PLATFORM

LéXPLORE Letters No. 3

This newsletter was generated on the 26-09-2022.

The figures below are showing data for the period 05-09-2022 to 19-09-2022.

Until today, the Idronaut sampled 3733 depth profiles on Lake Geneva. In this Newsletter we show 163 profiles, so just 0.04% of the recorded data. The complete data set is available at Datalakes.

Data highlights of this issue

In this issue we feature our Idronaut instrument, since Thetis got some well deserved maintenance checks. The Idronaut offers higher temporal resolution and goes 10 m deeper than Thetis.

The most striking event in this period is the huge mixing event around the 9th of September. A pronounced air temperature drop concurrent with strong winds and high waves shaked up Lake Geneva. This is visible in all water column plots, where we can see mixing down to 40 m depth. We see a dissipation of oxygen production and Chlorophyll maxima which is later reinstalled closer to the Lake surface. Speaking of Chlorophyll, the ratio of possibly toxic cyanobacteria in the phytoplancton mass is somewhere between 30 and 40% right now.

With air temperatures decreasing sharply after the middle of September, the water temperatures are moving away from being way to hot and closer to the climatological mean. By the way: In order to get high waves, we need not only strong winds, but also the right wind direction (preferably south-westerly). At the end of our time series, that did not seem to the case.

What is displayed

Data from the Idronaut profiler:

  • Water Temperature in °Celsius

  • Conductivity in mS/cm

  • Dissolved Oxygen in ppm

  • Phycocyanin, a measure of the abundance of cyanobacteria, in ug/L

  • Chlorophyll A in ug/L

  • Water pH

  • Salinity in ppt

Data from the automatic weather station:

  • Air Temperature in °Celsius

  • Wind Speend in m/s

Data from the wave buoy:

  • Wave height in decimeter

Authorship and further information

This newsletter is created by EPFL, specifically Martin Wegmann.

For more information about LéXPLORE, contacting us and possibilities to visit the platform: lexplore.info

If you want to know more about the Chlorophyll distribution across Lake Geneva, have a look at the satellite data map by our colleagues at CIPEL.

If you want to know more about the water temperature distribution across Lake Geneva, have a look at the lake reanalysis and forecasts by our colleagues at EAWAG.

If you want to use figures from the LéXPLORE Letters, you can use the following citation:

EPFL, Limnology Center 2022: LéXPLORE Letters, 3, https://lexplore.info/wp-content/uploads/2022/09/lexplore-letters-2022-09-26.html