9 July 2007:
At last a chance for another brief update. So much has been going on that we have all been extremely busy and with one exception, which I will come to later, the cruise has been a great success so far.

Having initially deployed the two tracer patches (one with and one without surfactant), the ASIS buoys and the URI float within only a few km of each other, we have seen their paths subsequently diverge. While both ASIS buoys have progressed to the south and westward at a mean speed of about 0.8 kt, the University of Rhode Island (URI) float moved initially to the northeast (a second URI float malfunctioned and was retrieved but it will not be redeployed). The URI float was in a three day cycle in which it spent significant periods below the mixed layer and was presumably driven by subsurface currents while ASIS was predominantly wind driven. Following remote reprogramming the URI float spent longer periods in the mixed layer and subsequently followed a course more similar to ASIS. Nevertheless by last night the separation between ASIS and the URI float was approaching 200km! Meanwhile the tracer patches moved towards the south and west. The first of these has now been abandoned due to SF₆ levels approaching background but the other is still good for a few days.

We have this morning retrieved the URI float and are proceeding towards ASIS 1 and 2 to redeploy it along with a new (third) tracer patch later this evening. Interspersed with sampling the tracer patches for SF₆ and helium-3 we have made successful deployments of the now repaired NIOZ Catamaran (you will recall that it was earlier damaged and capsized) and the PML surface sampler, both for microlayer and near-surface gradient work. Matt Salter has also collected microlayer samples by RIB for surfactant and bacterial diversity analysis on several occasions. We have also successfully deployed the NOC wave and bubble buoy on a couple of occasions and we also managed to lay out a surfactant patch in the path of one of the ASIS buoys, which subsequently passed through it. We took advantage of the fact that both ASIS buoys were moving in the same direction on parallel paths about 14 km apart. Thus we should have a good comparison between the two. Damping of capillary waves within the patch was quite clearly observable looking across the surfactant patch boundary through binoculars. There are also plans to release surfactant in the path of the NOC buoy next week; from this one we will also get sea surface photographs so the time in and out of the surfactant will be pretty precisely known. Overall the surfactant releases seem to have been a great success, at least from an operational point of view, but we will of course have to await full data analysis on our return home.

Overnight and where possible when the ship has been into the wind the University of Hawaii group have been measuring DMS fluxes while Steve Archer from PML has been monitoring DMS in surface waters. Comparison of transfer velocities derived from this data set with tracer, CO₂- and O₂-derived fluxes and transfer velocities, and the wave and bubble data will we hope, allow us to assess any "divergence" of gas transfer velocities between gases of differing solubilities at intermediate to high wind speeds. This is one of our major aims and like the surfactant deployments is rather novel.

Sadly it has not been good news across the board. Brian Ward's (Old Dominion University) ASIP (Air-Sea Interaction Profiler) malfunctioned during its third deployment and sank. It now lies crushed at the bottom of the Atlantic. Brian remains philosophical however, and he plans to work on a replacement on his return home.

2 July 2007:
We had a few hours delay to sailing due to a blown transformer on the NIOZ Catamaran and thus we had to wait a for a replacement to be couriered from the Midlands. So far we have put out both SF₆/³He tracer patches, one around 43°37.5'N, 17°03.0'W on 21 June and the other at around 43°31.5'N, 18°01.7'W on 26 June. The latter patch was deliberately smaller than the first and this was the one we covered with a much larger patch of surfactant, about 5 times the area of the SF₆ patch. This was to try and minimise the possibility of the surfactant slipping away from the SF₆. Initially it looked like this indeed might be happening but the next day we sent Matt Salter out in the RIB to investigate. The surfactant had spread out to cover a much larger area than the initial deployment and completely overlaid the other tracers which seemed to be somewhere near the centre, exactly what we had hoped for. The surfactant release was done as a series of parallel streaks about 250 m apart and about 2.5-3 km in length. These could be seen clearly from the deck as they spread out laterally and we have some really cool photos of them. We also successfully released the NOC wave rider buoy, the two ASIS buoys and the URI floats; however one of the URI floats had to be recovered today due to a malfunction. Not sure if it will be redeployed yet. Unfortunately the NIOZ catamaran suffered a major engineering failure on its first test. A motor came loose due to breakage of the sampler boom and sawed its way through one of the hulls. This caused listing and eventual capsize which drowned the electronics.

However the crew were as always able to expertly retrieve it and amazingly the samples remained intact. After several days of intensive repairs it now seems operational although a planned deployment today may be postponed due to worsening weather. Today surveying for SF₆ in the surfactant patch and hope to move on to the non-surfactant patch again later today before the low pressure passes through over the weekend. The University of Hawaii have been measuring eddy covariance DMS fluxes in and out of the surfactant although Steve Archer's DMS concentrations are low around 1-1.5 n molar. Meanwhile pCO₂ measured by the Montana SAMI sensor and the URI sensor, both in underway mode, has been around 340-350 ppm which we think is about adequate for the CO₂ flux measurements on ASIS. There is significant redundancy with respect to CO₂ because in addition to ASIS (Miami) and the underway data (URI) we will have direct flux estimates from AUTOFLUX (NOC).

Unfortunately the CASIX pCO₂ data have however been spuriously high throughout, having been well over 400 ppm, and at one stage around 480 ppm! The second ASIS was released N of the surfactant and we predict it will pass through the surfactant patch and out the other side, so we will get a good series of contrasting "in" and "out" measurements. It will be interesting to see what the coming low will do to the surfactant.