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.
News
I09N 2016 Weekly Report 5 Apr 26, 2016
From Leticia Barbero and Carmen Rodreguez **(Co-Chief Scientists)
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
transit to
Phuket, Thailand, where we expect to arrive on Thursday April 28th at 08:00 am
local time.
In this last week we completed the “bow tie” section of the cruise. We have
been so
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
casts,
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.
It feels
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
assistance.
Leticia and Carmen, Chief-scientists I09N.
I09N 2016 Weekly Report 4 Apr 19, 2016
From Leticia Barbero and Carmen Rodreguez **(Co-Chief Scientists)
Ahoy land-dwellers!
Greetings from the Bay of Bengal. We have now left behind the Equatorial
region of
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
whale yet,
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
values
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
decade.
On this week’s report we also wanted to talk a little about the LADCP
(Lagrangian
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
of
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
topography.
2) The strong currents associated with the Diamantina Escarpment are
associated
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
EKE
(roughly 17-30S) are elevated across the entire water depth.
The zonal equatorial undercurrents between the latitudinal bands of 5S~5N
which
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:
Onwards!
Carmen and Leticia, chief-scientists I09N
I09N 2016 Weekly Report 3 Apr 13, 2016
From Leticia Barbero and Carmen Rodreguez **(Co-Chief Scientists)
Ahoy land-dwellers!
This week started off with an issue around the carousel of the rosette. The
carousel
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
because
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.
On this week’s report we want to highlight some of the work being done as an
ancillary project of our regular GO-SHIP work. Scientists from UC Irvine and
the
Bigelow Laboratory for Ocean Sciences are conducting biological experiments
using
the ship’s underway water line as well as CTD samples. The samples will be
analyzed back on land to determine Particulate Organic Carbon, Nitrogen and
Phosphorous (POC, PON and POP, respectively). POP in particular had never been
measured in these waters prior to our cruise. They are looking at differences
in
C:N:P ratios and anticipate that because the South Indian Ocean Subtropical
Gyre is
a nutrient poor region, the C:P ratio will be higher here than in regions such
as the
equatorial upwelling region, for example. Other samples are collected from the
underway waterline to determine the surface phytoplankton community, and the
presence of genes indicating key nutrient sources. The group is also
conducting
incubation experiments to determine nutrient uptake rates. This will allow
them to
know whether microbes are using different nutrient sources (nitrate, ammonia
or
phosphate, for example). These studies are carried out in combination with
results
from trace metal analyses (we are doing roughly one trace metals cast per day)
and
data from our CTD nutrient samples.
In the plot below, there is a representation of the preliminary nitrate
concentration
values measured so far on the cruise and the location of 2 “regional
stations,” where
more intense biological sampling has taken place. One more “regional station”
is
planned close to 5 degrees North.
Amanda Fay, one of our CTD watch-standers modified a matlab program previously
coded by Seth Travis and Natalie Freeman (CTD watch-standers on I08S), that
allows us to have a look at the weather conditions predicted along our track.
We
continue to enjoy low waves and great weather, and from the privilege of our
calm
waters, we can appreciate the weather maps and watch as a huge storm with
predicted wave heights of up to 10 meters forms off the coast of Madagascar.
I09N 2016 Weekly Report 2 Apr 12, 2016
From Leticia Barbero and Carmen Rodreguez **(Co-Chief Scientists)
Ahoy land-dwellers!
Week 2 of our I09N cruise seems to have flown by as we have settled into our
routine of 3-4 stations per day. The weather has been fantastic and we have
been
working under calm seas. We can definitely tell that we have entered tropical
waters
now. The temperatures at the sea surface are around 30C (that’s 86 Fahrenheit)
and
we can feel the high humidity in the air. No one is complaining if they get
splashed
with the cool, refreshing water from the deep bottles anymore.
This past week we have sampled what will be our deepest stations of the
cruise,
reaching up to 6122 m depth. That is 3.8 miles deep! The sensors on our Rosie
(nickname for our rosette), however, can only withstand depths of 6000 m, so
we
had to stop her short. I am sure she was wondering why we didn’t lower her to
the
near-bottom, like we normally do.
While on one of these deep stations, the secondary conductimeter sensor of the
CTD
stopped working (not to worry, this is why we have 2 installed). The
conductimeter
provides a continuous profile of salinity, so it is an essential piece of
equipment in
the package. We replaced the faulty conductimeter while in transit to our
following
station, without any waste of ship time. A couple of days later we had to
replace the
primary conductimeter as well - so we are now working with two brand new ones.
At the same time, the oxygen sensor started to show increased scatter.
Normally,
only one oxygen sensor is installed, so it needs to provide a clean profile.
We did
some minor install modifications, tested all our spares, and are now back with
a
reliably functioning oxygen sensor.
We have just sailed past Cocos Islands. These small coral atolls belong to
Australia
and are located southwest of Christmas Island (see picture below).
Unfortunately
we were just a little too far to be able to see the atolls, but that didn’t
stop us from
learning about them. Apparently, two British captains (one Scottish, one
English)
rediscovered them in the 19th century and planned to settle there. One came
with a
harem of 40 women. The second came shortly after with his family for a more
traditional settlement. As you can imagine, these 2 groups didn’t get along,
especially after some women from the harem started deserting to live with the
sailors of the second group. Another interesting fact? Charles Darwin stopped
there
during his journey of discovery aboard the Beagle. Participating in a GO-SHIP
cruise
always brings with it the chance to learn interesting little facts about
remote parts
of our planet!
On Sunday April 3rd, at approximately 16:30 local time, while on station 115,
we
had a loss of communications with the CTD which was then at 3000 m depth and
coming up. We recovered the package and determined that one of the conductor
cables had shorted. The winch cable has three electrical conductor cables
inside that
are used to communicate with the rosette while it is in the water.
Fortunately, only
one conductor is needed, so we switched to an alternate one in the winch and
have
proceeded with sampling, redoing a cast on station 115. There will be no
impacts to
our science plan as a result of the time invested in reterminating the cables
and no
modifications have been made to our station planning.
We have also been deploying ARGO floats at select locations along the way.
ARGO
floats are free drifters that stay “parked” at a predetermined depth (normally
around 1000 m). Every 10 days or so, they descend to 2000 m and profile the
temperature and salinity on the way back to the surface. These profiles, along
with
the surface GPS position, are then sent via satellite to the labs overseeing
the
drifters. There are currently over 3000 ARGO floats providing us with T-S data
from
all the world’s oceans, and around 800 need to be deployed every year in order
to
keep the array active. By the end of this cruise we will have deployed 8 new
floats.
Science never sleeps on this cruise. Next week we will be talking about our
underway measurements, so stay tuned for that!
In the meantime, you can check our cruise blog:
One of our CTD-watch standers, Amanda Fay, is also chronicling her experience
in
her own blog:
Onwards!
Carmen and Leticia, chief scientists I09N
I09N 2016 Weekly Report 1 Mar 30, 2016
From Leticia Barbero and Carmen Rodreguez **(Co-Chief Scientists)
Ahoy land-dwellers!
The third occupation of the Global Ocean Ship-Based Hydrographic Investigation
Program
(GO-SHIP) I09N line (“I” for Indian Ocean) is underway and has just completed
its first
week. During the next 5 weeks we will occupy over 100 stations, closely
following the
station planning of the last two I09N cruises.
Most of the equipment we will use was already set up for the previous GO-SHIP
cruise, I08S,
and so, most of the science crew were able to enjoy some time off in
Fremantle/Perth
(Australia) prior to our departure. We did have a new group from the Bigelow
laboratory
setting up equipment. They are going to be measuring trace metals as well as a
whole suite
of biological parameters (genomics, phytoplankton abundance, nutrient uptake,
etc) both
from underway samples and Niskin samples, through filtration and incubation
experiments.
All their hard work will add an exciting new set of biological data to this
GO-SHIP line.
Prior to departure, a lot of time was devoted to extensive testing of the
winch system (called CAST 6)
to make sure the cable would not be experiencing too high tensions during
deployment and recovery. This
winch is responsible for safely taking our equipment into depths of up to
6000m. The rosette (aka CTD)
represents the core of our sample operations. It has 36 10-l bottles which
collect water at depths of our
choosing, from the ocean floor to the surface. From these bottle we collect
samples to analyze a wide
variety of parameters, ranging from oxygen concentration, pH, and salinity, to
lesser known
parameters like colored dissolved organic matter or nitrogen isotopes.
During our 4-day steam to reach our first station, our CTD-watch standers were
trained on
CTD console procedures. Some of us also received training on how to operate
the A-frame
and winch that are being used for the trace metal casts. Because the
concentration of these
metals in seawater is extremely low, samples cannot be obtained from the
Niskins on the
rosette (which is made of metal) and need to be obtained from special Niskin
bottles, using
a non-metal cable.
While underway our students helped launch XBTs every day. These are expendable
bathythermographs that provide a profile of temperature and salinity. There
was a bit of
discussion on whether they should be called “launches” or “shootings” just
based on the
deployment system.
So far we have not seen a lot of wildlife other than flying fish, but we are
already warning
everyone to wake us up should whales or sharks decide to come out and play
close to our
ship while we are sleeping. Here’s hoping!
We are having good weather and relatively calm seas (knock on wood) and are
making good
speeds in between stations. Right now we are at 21.32OS, 95.00OE doing station
- Everyone is in good spirits and work is progressing smoothly.
Onwards!
Carmen and Leticia, chief-scientists I09N
I08S 2016 Weekly Report 4 Mar 17, 2016
2016 I08S Weekly Report 4 From Alison Macdonald (chief scientist) and Viviane Menezes (co-chief scientist)
Only three days of sampling left. How could it have all gone so quickly? A week ago we were delighting in positive single digit oxygen temperatures. Our early morning deployment going in at 00:47 (local) and coming up now had surface temperatures of greater than 20°C. Not so long ago the students were learning to tie knots they had never heard of and tagging the rosette sometimes seemed like a hopeless fishing exercise. Now they tie, tag, and hold their lines like professionals. So, is it surprising that even as we wonder at the never-ending supply of crisp lettuce; even as dig deep in our personal stores for offerings to our sample log candy bowl; even as we whip along deploying, recovering and sampling at an impressive efficient clip, that discussion around the rosette should wax nostalgic. We only get to do this X more times. Who gets to do the last deployment? I’ll never have to sample 23 again. Who will sample the last salt? After all even with 38 days at sea, we’ve only had been sampling for three weeks. Who wants to do this again?
This past week we have been managing 4 stations a day. With a 36-bottle rosette and bottom depths less than 4500 m, analysis can’t keep up so we took a two-hour break from deployments yesterday. The delay had the added bonus of giving CDOM a chance to better time their optics cast with satellite fly over. In spite of our efficiency we have still be presented with some challenges. Last Friday we found the floor of hangar slick with what turned out to be oil from a loose hydraulic fitting. We had a couple of casts where we were sliding carefully (and in some cases moon walking) around the rosette until the source of the leak was discovered and a major effort was put out by the crew to clean up both the hangar and deck. And then there was station 59, which took our breath away, but thankfully not our rosette.
Between stations 58 and 59, a precautionary mechanical retermination was performed as the wire was beginning to show signs of wear. On recovery at station 59, as the rosette was being brought in, the termination failed. The rosette hit the boards and then teetered for a terrifying moment on the rail before the winch regained enough control to bring it in. Thankfully, no one was hurt and none of the instruments showed any sign of new issues after this incident. Kudos to our tag-liners who did an excellent job keeping their lines under control. A complete retermination was performed before station 60 and we’ve had no issues since.
Lest you think the science has suffered from these adverse adventures check out our bottom waters: a) the strong CFC (and SF6) signal in the abyss following the line north (57.5°S - °45.6°S) and b) the impressive warming and freshening compared to earlier occupations in our stations between 63°S and 51°S (contours σ4).
The other day our white board read: “Success consists of going from failure to failure without loss of enthusiasm” (Winston Churchill). We have hardly failed, but we have definitely had some challenges. Yet even we as run out of stations, we have not lost enthusiasm. Taking advantage of our last deep-ish casts, cups are in full production. We fully intend to make it to our final planned station at 28°S before turning east for our 4 day transit back to Fremantle.
I08S 2016 Weekly Report 3 Mar 5, 2016
From Alison Macdonald (chief scientist) and Viviane Menezes (co-chief scientist)
Here
we are at week three. When last you heard from us, we were some 1100 km to the
south. Now not only have our water temperatures risen out of the realm of
negative numbers, we seeing surface temperatures as high as 6°C or more. Not
quite subtropical, but certainly more bearable for sampling. We have left the
icebergs behind and although we saw one last penguin a couple of days ago we
are well on our way north.
Over the last week we have been working out the kinks in our replacement rosette. As we began using the DASH-5 system, our students were trained in deck operations for deployment and recovery - a plus for their sea-going experience. Unfortunately, no sooner had we begun using the new system than we had to find work-rounds for wire monitoring issues. It seemed like we had it all under-control when a few days ago the winch jammed at 2000 m and a very long and tedious shift ensued as the rosette was brought up at 4 m/minute. But, we have seen worse and we count ourselves lucky – at least we have a rosette to bring up. We have since moved back to our other winch, but are not using the docking system. To get this working took a few trials, first with a weight and then with the rosette. All is now going smoothly.
V.
Menezes
Satellite
sea surface anomaly and absolute geostrophic currents for Feb 24, 2016
(stations 21-26). Pink squares show the I08S stations. Near real time
altimetry data are courtesy from IMOS. (V. Menezes)
We are working our way through the eddy field that forms as the Polar Front passes the northern edge of the Kerguelen Plateau. Velocities upward of 1.5 m/s test our ability to both stay on station and keep the wire angle reasonable. They also make for speedy departures of floats and drifters. We have now deployed 10 surface drifters for the Global Drifter Program and 4 bio-floats for SOCCOM program. Just today we received the first profiles from these floats (below).
K.
Johnson
As we finish this report we have left the furious 50s and have headed into the roaring 40s. We are glad to be moving – see what is coming (below, courtesy of passageweather.com, overlay by S. Travis.)
I08S 2016 Weekly Report 2 Mar 5, 2016
Please note that the bulk of this report was written prior to the events of Monday afternoon Feb 22, 2016 (local), which are explained in the last paragraph.
Steaming somewhat more slowly than planned through rough seas and then around to the west to avoid ice, it took us 11 days to transit from Fremantle to our first station. But, it thought well worth it by most of us as at 66.60°S, 78.4°E, we were 0.05° south of the Antarctic Circle. As we made our way into Prydz Bay we were treated to the night skies filled with the Aurora Australis and some beautiful views of icebergs (kept at a safe distance).
Sampling has been busy, but is going well as the CTD watch learns the ropes. There have few glitches other than a couple of short hold ups with the winch, which were quickly dealt with, and the switching of the intake source for the underway measurements first due to bubbles and second due to issues with the pump. Our first SOCCOM float was successfully deployed with all necessary sampling on Sunday night. And our first drifter deployment will be coming up in a few days.
It seem the cooks in the galley are planning on fattening us up before we get back on land as along with wonderful meals, we are constantly tempted with fresh baked bread, muffins, cakes (birthday and otherwise), cookies, croissant, crumbles, and even pavlova for deserts. A couple of nights ago despite of freezing temperatures and the occasional snow shower, we were treated to barbequed steak (cooked outside).
Yesterday, as most of you are already aware, just after noontime, under normal conditions, the rosette was going in when a malfunction of the Cast-6 system caused the wire to part
and the loss our 36-bottle rosette, (seen in the photo above, note the iceberg in the background is not nearly as close at it seems) including all instrumentation in 2200 m of water. To trawl for the rosette with no certainty of success would have required the efforts of many of the same personnel needed to get the spare rosette and alternate winch prepped. Given our previous delays due to weather and ice, it was fairly quickly decided that the best course of action would be to move forward with the science. I am most grateful to have this steadfast crew and science party out here as within less than one shift we had a working rosette with CTD, transmissometer and fluorometer in the water again. Spare chi-pods should go on today. The loss of our specialized fluorometers for the SOCCOM floats will be felt, as will the upward/downward looking pair of LADCPs. We are once again moving steadily northward along the track of the 2007 occupation of I08S. The students are enthusiastically embracing the joys of deck work: hooking the rosette, slipping the lines and learning to tie knots. Our station spacing will likely suffer due to the loss of time and some observations will simply not happen due to the loss of instrumentation,. Nevertheless, the science will not suffer due to a lack of effort.
Coming north,
- Alison and Viviane
