Diary

R/V Pelagia Cruise BSIK/LOCO-IW/Towed ADCP

Friday/Saturday – 9/10 June 2006

Photo: Chrysanthi Tsimitri

- Friday 09 June-

Underway to last large mooring deployment site, steaming fast. Most of today we spend preparing tomorrow's mooring and, especially, frantically checking the huge amounts (over 2 GB) of data we collected yesterday. The last large mooring was successfully recovered and all instruments have delivered the expected amount of data over the full period of 19 months.

But, the vastest amount of data was to be collected from the two short-term moorings, which we deployed 19 days ago near the rim of Great Meteor Seamount. These moorings carry instrumentation that is sampling currents and temperature very fast (once per second) resolving short distances (every 0.5 - 1 m in the vertical). In this way we can actually see internal waves bashing into the sloping topography:

more than 50 m high backwards breaking waves are not uncommon that pass a mooring within a minute. Such vigorous waves are accompanied by sudden changes in current direction and speed (from 0 to 1 knot in 10 seconds) that completely dominate the transport of sediment, up the slope (not downward). These phenomena were first revealed using our temperature sensors that are built at NIOZ, mainly by the MTE and MTI departments.

After 10 years of several versions and many trials, we now deployed version NIOZ3 for the first time: 101 independent temperature sensors. Relief was great ("yesz") when all sensors could be cut from the line to which they were 'yellow'-taped (see photo); relief was also great that 98 had delivered good data and that there is the prospect of 0.6 GB of fresh data implying hard analysis work to be performed in the near-future.

- Saturday 10 June -

Successfully deployed our last long-term mooring. Presently we are heading towards Funchal, Madeira, where we expect to arrive tomorrow, Sunday, late afternoon (our time). In this area of the Atlantic Ocean, roughly between Madeira and the Cape Verdes, we have left behind some 40 current meters and 100 temperature sensors on 8 moorings that we hope to find back full of data when we return, in October 2007.

Best wishes, Hans van Haren