R/V Roger Revelle Expedition KNOX03RR

CLIVAR/CO2 cruise I8S

Chief Scientist Weekly Report 5, 05 March 2007

1600 local; 42.5 °S, 95.0 °E; air temp 14 °C (59 °F), wind 12 knots from West

We have now completed 59 stations on our “I8S CLIVAR/CO2 transect” (known in the ocean carbon community as the “I8S CO2/CLIVAR transect” - it’s all a matter of perspective). We have been operating steadily and successfully with the older CTD cable we switched to last week. That is tied for Best News of the Week with the fact that the weather and seas, though often far from ideal, have stayed within our CTD/rosette operational limits for the entire week. Lowering was often slowed by the motion of the ship in swell, but casts have never stopped for weather since the time of the last report. This has enabled us to make good northward progress, maintaining the planned 50 km station spacing without undue lost time.

Long simmering problems with the lowered acoustic Doppler velocity profiler (LADCP) instruments boiled over the past week. The LADCP is a self-contained package that is deployed on the rosette for each cast. The resulting data yield an ocean velocity profile from top to bottom. Three LADCPs were brought on the cruise, two newer 300kHz “workhorse” models (usually used in pairs), and one older “broadband” 150kHz instrument. The 300kHz instruments typically only perform well in regions of high scattering (e.g. high latitudes, due to higher productivity overall) so the plan was to use the 300kHz instruments for most of the first leg, and switch to the 150kHz instrument when scattering levels dropped in the desert-like subtropical gyre.

One of the 300kHz instruments was an experimental model with higher power and was to be field-tested during this cruise. That instrument has now been rendered moot until its bulkhead connector can be replaced (in Fremantle). The remaining (more typical) 300kHz instrument has been used successfully until recently when it started returning casts with incomplete data. The cause is unknown. We have switched to the 150kHz instrument and hope it continues to perform well for the duration of the cruise. It is heavier than the 300kHz instrument, and its extra weight may be helping the rosette sink better, too.

In addition to the usual cast of officers, crew, researchers, and graduate students, we have a three-person public outreach team along with us on leg I8S. In delving into the grit of oceanographic fieldwork, they hope to improve public understanding regarding how data that reflect the changing state of climate are collected. They plan to produce a website, several articles, and multimedia features. Their role on the ship has been purposefully nebulous, something of a hybrid between research assistants and a media crew. We have integrated them into the science team by assigning them tasks that are, in their words, “difficult to ruin”. Their project continues to evolve based on the materials they gather and the opportunities that arise. They have been shadowing the scientists and shipboard technicians on their daily rounds, and are busy turning interviews into short articles and film clips about our research. Captain Murline has helped considerably regarding coordinating the part of their work that provides a sense of the foundational support needed to run a cruise.

Meanwhile, the cruise continues at its design pace. The weather is warmer, to the point that it can be comfortable in the sun if one is out of the wind. Well fed, well looked after, and with no shortage of samples to run, we plug away towards an end-of-sampling now less than ten days away.

Jim Swift and Annie Wong

chief and co-chief scientists, CLIVAR/I8S