US GO-SHIP is part of the international GO-SHIP network of sustained hydrographic sections, supporting physical oceanography, the carbon cycle, and marine biogeochemistry and ecosystems. The US program is sponsored by US CLIVAR and OCB. Funded by the National Science Foundation and NOAA.
Prepared by Brendan Carter
A map of our section, with the yellow arrow highlighting what we’ve done this week. We have now emerged from the French and Mexican EEZs (red circles) with a complete set of measurements from each region. French? In the middle of that circle we passed through is a small island claimed by France named Clipperton. It is still the closest land to us.
It has been a pretty good week. We’ve hit our stride, and have begun completing our station work quickly and efficiently. We did 29 stations across 13.5° between Nov 28th and Dec 5th. The Brown has been averaging more than 10.5 kts between stations, our team is sending the CTD-sensor rosette package down to 10 meters off the ocean floor and bringing it back filled with water as quickly as we’d hoped, and we’ve had calm weather and no additional major delays. Our quick pace perhaps feels faster still due to the ~3700 m average depth of the stations, which is a bit shallower than many of our veteran repeat hydrographers are used to. We are testing the throughput of our teams various analytical systems despite using a 24 position rosette (vs. the 36 position rosettes that bring back 150% as much seawater).Read More
Prepared by Brendan Carter
We are pleased to report that we are making our way south out of the Mexican EEZ and doing station work as we go. We were briefly faced with the difficult decision between waiting on station and abandoning the work in the Mexican EEZ. Some offshore islands make the Mexican EEZ more than twice as thick as the default 200 nautical mile (nm) limit along our track. This meant that going south to accomplish work outside of the EEZ while we waited was not a good solution, and also that an unusually large amount of station work (~15% of leg 1) would have been lost if we had given up on the EEZ. Ultimately, we spent nearly a day and a half waiting on station. We are now slightly behind our ambitious schedule, but relieved to be able to fill in these important measurements of the oxygen deficient zone (ODZ) off Mexico.Read More
Prepared by Brendan Carter
After one more delay that pushed our sailing date back to 1500 on Saturday, Nov. 12th, we are excited and relieved to be underway.
This was the original start of this report written on Nov. 13th. Unfortunately, we since returned to San Diego for diagnosis and repairs to the port Z drive. It was an approximately 48 hour round trip followed by an additional 5 days in port with 2 sea trials. We are pleased to again be about a day from port and heading to the P18 line. The modified schedule has us getting to Easter Island around Christmas. The date of the Punta Arenas arrival at the end of leg 2 is less certain. This report contains an updated timeline of issues affecting the P18 schedule at the bottom (dates of new updates are in bold).Read More
Prepared by Brendan Carter
The first leg of the P18 GO-SHIP project was scheduled to begin Monday Nov. 7th, so I owe an update. However, “Report 0” is being saved for the day we depart from San Diego, CA for the first station on the P18 line at 110°W. Hence “Report -1.” The delay of our start date owes to lingering mechanical issues on the NOAA Vessel Ronald H. Brown (henceforth the “Brown”) that were identified after a dry dock period in San Francisco, CA. A timeline of the repairs and discoveries can be found at the end of this update. Our working departure date estimate is now Thursday Nov. 10th.Read More
Follow scientists as they work on the R/V Ronald H. Brown.Read More
Mission accomplished! We are happy to report that we have now completed all of
our science objectives…and then some!
We finished our last station on Sunday afternoon at 19:50. We are now in
Phuket, Thailand, where we expect to arrive on Thursday April 28th at 08:00 am
In this last week we completed the “bow tie” section of the cruise. We have
lucky weather- and instrument-wise that over the first 4 weeks we gained enough
time to be able to add 2 bonus stations. Since our last planned station was at the
border of the Indian EEZ, we couldn’t add any extra stations further north. Instead,
we extended the bow tie section westward to re-occupy two additional stations
from the I01E WOCE line. We went as far west as possible without entering Sri
Lankan EEZ waters, up to 84.75W, and then continued with the rest of our planned
stations. These two extra stations allowed us to sample an area with particularly
high carbon in the bottom waters and fresher surface waters. There should be some
interesting results from these samples.
Over the last 5 weeks we have done a total of 113 stations, plus trace metals
optics casts and continuous underway sampling (while on station and in between
stations). Even leftover water from the niskins was used for unplanned
measurements to be run back in our labs. We have an excellent quality dataset to
work with when we get back to land. As we moved northwards we observed a
freshening of surface waters, a drop in subsurface oxygen levels, high carbon
concentrations in the western region, and I’m sure we have a lot of interesting
biogeochemical information that will come from all the samples to be ran back in
our home labs.
On this cruise we have had two groups in charge of carbon measurements (NOAA
for underway pCO2 and DIC, and UCSD for pH and alkalinity). GO-SHIP is one of the
few programs where the CO2 system is over-determined (i.e. where we measure
more than 2 of the 4 parameters that characterize the carbonate system). This
enables us to evaluate not only the carbon exchange with the atmosphere, or
changes in carbon storage over time, but also to evaluate the quality of the
measurements themselves (e.g. by comparing measured DIC against the value
calculated from pH and alkalinity). Below you can see preliminary results for this
comparison. The average difference between measured and calculated DIC values is
2.1 ± 1.8 μmol/kg. This speaks highly of the quality of the measurements. Great job!
I think everyone on board agrees that this has been a very successful cruise.
good to go home with a sense of accomplishment, but it probably feels even better
just to know that we will be setting foot back on land in just a couple more days.
Don’t forget to check our blogs for new entries:
We want to thank everyone on board, science and ship’s crew alike, for a great
cruise. Thank you also to the people back on land who provided shore-side
Leticia and Carmen, Chief-scientists I09N.
Greetings from the Bay of Bengal. We have now left behind the Equatorial
the Indian Ocean and have finished an intense sampling scheme between 3S and 3N,
with stations spaced just 20 nm apart instead of the average 30nm. We completed
20 stations in just 6 degrees of latitude. Now we are covering the so-called “bow tie”
section of the cruise, where the track makes a funny kind of knot around 10N (see
plot below). This “bow-tie” section covers part of the I01E GO-SHIP cruise which
was last occupied in 1995 but not again. During the I09N 2007 cruise, sections of the
I01E track were also sampled, and we are repeating this track, going as far west as
international waters will allow. The Bay of Bengal is an important source of fresh
water to the global ocean and these stations are useful for estimating freshwater
transports and budgets, among other things. The stations further west also have
interesting carbon and nutrient concentrations, particularly in deep waters.
We are beginning to see some animals out there, finally. Still no sign of a
but some of us have seen the odd turtle, a small shark, and a school of dolphins
splashing in the distance. To compensate for the lack of exciting fauna, the Indian
Ocean is providing us with a non-stop series of amazing sunrises, sunsets and starry
skies, as well as ongoing calm seas.
For those of us who have not worked in the Indian Ocean before, the oxygen
we are seeing have been a surprise. Starting at around 10S, subsurface values began
to drop significantly and we have actually measured O2 values as low as 10 μmol/kg,
compared to values of ~200 μmol/kg at the same depths in our first stations. This
means that subsurface waters in this area are highly hypoxic, and close to the
suboxic range (concentrations lower than 5 μmol/kg). In the suboxic range most
organisms cannot survive. Similarly low O2 concentrations had been measured in
this area in previous cruises so this is not a dramatic change that occurred in the last
On this week’s report we also wanted to talk a little about the LADCP
Acoustic Doppler Current Profiler) measurements. The LADCP is installed on the
rosette and provides zonal as well as meridional current velocities. These currents
are important not only for physical oceanographers, but also for researchers
working with nutrients and carbon, because knowing them helps scientists in
determining nutrient distribution and transports.
Our LADCP scientists on board and back on land, Takaya Uchida and Andreas
Thurnherr, have summarized the main results from the LADCP records so far:
1) There are strong currents along the Diamantina Escarpment (southern flank
Broken Plateau, near 30S) essentially all the way to abyssal depths. From this single
occupation it is not clear whether the northwestward flow along the Diamantina
Escarpment is part of the mean circulation or if it is a transitory feature. The flow
above the topography crosses the plateau in a southwesterly direction; the flow
below the crest depth appears to flow along the topography (probably because of PV
conservation). Based on this observation we hypothesize that the southern limit of
the high-EKE (Eddy Kinetic Energy) wedge seen in the figures below is set by the
2) The strong currents associated with the Diamantina Escarpment are
with significant turbulence and mixing. Based on the VKE (Vertical Kinetic Energy)
parameterization the turbulence levels around the Broken Plateau are similar to the
turbulence levels in the ACC region, although they do not extend above 1000m.
3) The VKE-derived turbulence levels under the entire region of high surface
(roughly 17-30S) are elevated across the entire water depth.
The zonal equatorial undercurrents between the latitudinal bands of 5S~5N
are specific features in the equatorial regions can also be clearly observed.
As always, here are the links to our blogs for those of you who want to
learn more about what’s going on in our cruise:
Carmen and Leticia, chief-scientists I09N
This week started off with an issue around the carousel of the rosette. The
is the mechanism that triggers the closing of bottles (bottle tripping) in the rosette
(see pic below). On a couple of stations, problems with communication in the
rosette prevented the surface bottle from tripping. It was determined that there was
damage to the bulk connector of the carousel, which could have forced us to switch
to our spare 24-bottle carousel (thus losing some of our vertical resolution).
Eventually the connector was repaired and we now have reliable communication
with the rosette during the casts. We were also able to keep using the Y-cable that
allows communication between the carousel and the SBE35 reference temperature
sensor. Special kudos to the ODF team, especially Sergey, Matt, Ted and Courtney,
for committing to diagnosing the problem and fixing the connection with minimal
loss of time.
On the same note, we have been forced to take Niskin 12 out of the rosette
the magnet operating the trigger mechanism is damaged and the bottle was not
tripping. Given that we are now moving towards shallower depths (all the stations
deeper than 4500m are now behind us), we think that the science objectives will not
be significantly impacted.