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Conditioning SAMW
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2020
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Thomas G. Thompson
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Project Title: |
Collaborative Research: Biogeochemical and physical conditioning of Subantarctic Mode Water in the Southern Ocean |
Project Status: |
Submitted |
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Principal Investigator: |
William M. Balch, Bigelow |
Project Institution: |
Bigelow |
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Project ID: |
105633 |
Version #: |
6 |
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Date Submitted: |
2/8/2017 5:03:00 PM |
Created By: |
William M. Balch |
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Date Last Modified: |
2/7/2019 1:50:00 PM |
URI Serial #: |
None |
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Funding Agencies: |
NSF/OCE/CO - 1735664 - Funded |
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Summary of Field Work: |
We are proposing two cruises out of Durban, South Africa,(returning to Durban, S.A.) to sample the chemical conditioning of SubAntarctic Mode Water (SAMW) around the region near the Crozet Islands and its effects on subsequent growth of minerogenic phytoplankton as that water is subducted towards the north. The two cruises would be during the austral summer of January 2020 and 2021. The total length of the cruise track from Durban, S.A. to the study site and back to Durban is ~5930 nautical miles. We will study the conditioning of carbonate chemistry as well as, nutrient and trace metal chemistry of SAMW by coccolithophores and diatoms, each of which is abundant in waters of the SubAntarctic Front and Polar Front, respectively; both algal groups are major players in ballasting of particulate organic matter and driving the ocean's biological pump at the site of SAMW formation as well as northwards into subtropical and tropical waters.
The first cruise (January 2020) will involve two parts: surveying two mesoscale eddies (A) one that is rich in coccolithophores, examine how the carbonate, nutrient and trace metal chemistry changes over a time scale of a month cruise in these mesoscale, semi-enclosed water masses. These observations will be compared to (B) a low-PIC eddy and its associated changes in carbonate chemistry. We also will perform nutrient/iron-addition (or 0.2um-filtered, deep SAMW water addition) experiments aboard the ship to examine factors that are limiting phytoplankton growth. Lastly, we will perform a section between 60oS and 30oS, along the 55oE meridian to provide the larger-scale view of the rate of conditioning of the subducting SAMW, both at the site of formation by the diatoms of the Polar Front and the coccolithophores of the Great Calcite Belt, or further to the north as the water heads towards the equator. The second cruise (January 2021) will not repeat the meridional section between 60oS and 30oS. Instead, that cruise will focus exclusively on surveying four more eddies in the region as they are shed from the Subantarctic Front and Polar Front and move water to the north and west. Vertical water sampling will go through the base of the eddies and reach vertically down to the SubAntarctic Mode Water (as deep as 1000-1500m). We are offering to the SOCCOM program (Southern Ocean Carbon and Climate Observations and Modeling) to help them deploy new profiling fronts in this poorly-sampled Indian Ocean region (see letter of commitment in the proposal from J. Sarmiento) and will use SOCCOM data in our study of SAMW conditioning. |
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Summary of Facility Requirements: |
We will need facilities for the following work:
1) Isotope van for 14C tracer work
2) UNOLS trace-metal clean van
3) Metal free block/sheave for running Kevlar line through (Balch will bring (non-conducting) line to put on the Sperry deck winch for hanging bottles). We need to keep the Kevlar line clean in terms of trace iron contamination.
4) Bow-mounted radiometers (several years ago the R/V Revelle fabricated an elegant mount for us to do this which they may still have on the ship.
5) Flowing seawater system for underway measurements of optics and SAMI pCO2 system
6) Video Plankton Recorder (supplied by Bigelow Laboratory) will need to be mounted on the ship's quarter at the stern for performing detailed eddy sections.
7) CTD/hydrocast capabilities
8) Fume hood (for working with acetone)
9) Access to Met/Nav data
10) ADCP
11) Thermosalinograph data
12) Marine tech support for running nutrient (NO3, NO2, PO4, Si(OH)4), NH4, DO and Salinity at ~76 profiles, plus running nutrients on four carboy experiments.
13) We will need space on the fan tail for flow-through seawater incubators. They have a foot print of 4' x 4' and we expect to have at least four of them. These will be to incubate carboys in ambient seawater plus smaller bottles for primary production/calcification incubations. We would have one temperature control unit for maintaining the temperature where the water was sampled over 3-4d periods.
14) Co-investigator McGillicuddy (and his research associates) will be helping with the VPR surveys, and using the ADCP data for defining current velocities.
15) At the centers of each surveyed eddy, we will deploy a lagrangian drifter equipped with ARGOS in order to center the ship surveys. The drifters will be recovered after the survey is complete.
16) If possible, we would like to load as much as possible of equipment, hazmats, radioisotopes, gases in a US port before the ship sails . We fully understand that this must be cleared at multiple levels and is not a "given". |
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Summary of other requirements and comments: |
The cruise tracks are designed in order that the available time for dedicated science on station is 5d out of the 38 days requested (with one weather day built in). There will be several types of station sampling: 1) underway sampling for hydrography and optics, 2) CTD no-water, 3) CTD with water (for measuring everything except productivity), 4) CTD with water including productivity and a separate cast of trace-metal clean Niskin-X bottles, 5) VPR deployments, 6) in-water optics sampling, 7) two drogued drifters equipped with ARGOS transmitters will be deployed in the core of each eddy to mark the eddy center and 8) four incubation stations for carboy incubations with nutrient or iron additions will be performed in the first cruise (in the second cruise, there will be 8 carboy experiments); 9) CFC's will be measured (water samples only) on the meridional transect in cruise #1 in order to age the SAMW.
The reason for this stratified sampling is related to both finances and time. Underway sampling will provide us the fastest way to survey each eddy. Productivity stations are the most costly in terms of supplies, wire time and technician time to process. At the other extreme are CTD/no-water casts which can be done quickly and cheaply. Thus, we are planning ~149 CTD casts for the trip, half of which will involve collecting water (the other half would be CTD only) which will provide a horizontal resolution of the hydrography of ~80km. We will sample at finer scale near the eddy edges since gradients will be stronger there. Profiles of other discrete water samples (including chlorophyll, POC, PIC, DIC, cell counts, biogenic silica, CTDs, etc.) will be measured at ~75 stations (with effective station spacing of ~160km). Productivity casts will always be done pre-dawn and will include all particulate analyses and CTD measurements. The incubations will always run for 24h. There will ideally be one productivity station per day or about 34 for the cruise (station spacing for productivity/calcification will be ~400km). A free-fall optical profiler will be deployed at local apparent noon when sea-state permits and skies are clear (thus maybe 10 profiles per cruise leg?). These provide subsurface radiance and irradiance estimates as a function of depth, which can be inverted to derive inherent optical properties (that can be related to POC and PIC distributions). Carboy experiments will be conducted on the main deck involving nutrient and trace metal limitation . There will be 4 such experiments over the course of the first cruise and 8 experiments in the second cruise. |
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Type of Request: |
Primary Ship Use |
Request Status: |
Submitted |
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Request ID: |
1009125 |
Created By: |
William M. Balch |
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Date Last Modified: |
2/7/2019 1:50:00 PM |
Date Submitted: |
2/8/2017 5:03:00 PM |
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Year: |
2020
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Ship/Facility: |
Thomas G. Thompson
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Optimum Start Date:
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1/7/2020 |
Dates to Avoid: |
The coccolithophores that we will be studying peak during austral summer in January/February (and diatoms can still be found further to the south) |
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Earliest Start Date: |
1/1/2020 |
Multi-Ship Op: |
No |
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Latest Start Date: |
2/1/2020 |
Other Ship(s): |
We are open to using other vessels, if necessary, in the interest of getting the work done. |
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Operating Days Needed: |
Science Days |
Mob Days |
De-Mob Days |
Estimated Transit Days |
Total Days |
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38 |
3 |
1 |
1 |
43 |
Repeating Cruise?
(within same year) |
No |
Interval: |
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# of Cruises: |
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Description of Repeating cruise requirements: |
N/A |
Justification/Explanation for ship choice, dates,
conflicts, number of days & multi-ship operations: |
1) Our proposed work is to target mesoscale eddies that are pinching off from the Subantarctic Front in the Southern Ocean. These eddies contain high concentrations of coccolithophores (which we can observed from ocean color satellite imagery). In our proposal (Fig. 7C), we highlighted two coccolithophore-rich eddies from February, 2012, northeast of the Crozet Archipelago, that were at 50oE x 36oS and 56oE x 38oS. Obviously, the exact locations of future eddies will not be known until the time of the cruise. Our continuous underway measurements which will begin 24h after we depart from port are to help us as we navigate to the center of these eddies (and know when we have arrived). The location that I put for the first and last science station below is an average of these two eddie locations [37oS x 53oE]. 2) I originally chose Durban, S.A. as the port of embarkation and disembarkation as the nearest port to get to get to these eddies, to save the most ship transit time. That said, we can be extremely flexible regarding ports of embarkation and disembarkation if this makes it easier for where ever the ship is coming from (as long as we can get the necessary science days in the region). |
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Short Description of Op Area
for use in schedules: |
S. Ocean |
| Description of Op Area: |
55oE, 30oS to 60oS |
| Op Area Size/Dia.: |
1500 |
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Lat/Long |
Marsden Grid |
Navy Op Area |
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Beginning
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Ending
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Show Degrees Minutes |
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Foreign Clearance Required? |
Yes |
Coastal States:
France, South Africa |
 Important Info on Foreign Research Clearances
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Are you or any member in your science party bringing in any science equipment items which are regulated for export by the International Traffic in Arms Regulations (ITAR) and/or the Export Administration Regulations (EAR)?
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No |
If yes, have you applied for the necessary permits through your export control office?
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No |
| Questions about ITAR/EAR regulations?
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Comments about foreign clearance requirements or
description of any other special permitting requirements
(e.g., MMPA, ESA, IHA, Marine Sanctuaries, etc.) |
I'm not aware of any special permitting requirements (other than the foreign clearance). |
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Requested Start Port |
Intermediate Port(s) |
Requested End Port |
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Durban, South Africa |
None |
Durban, South Africa |
Explanation/justification for requested
ports and dates of intermediate stops
or to list additional port stops |
Durban is the closest port for accessing the Crozet
Islands. The transit there would take us across the Aghulas, Sub Tropical, Sub-Antarctic fronts, regions that we wish to study. If we use a different port, we'll still likely cross these important frontal boundaries. |
Important Info on Working in Foreign Ports
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Chief Scientist: |
William M. Balch, Bigelow |
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# in Science Party |
28 |
# of different science teams |
6 |
# Marine Technicians to be
provided by ship operator:
(include in science party total)
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4 |
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Explanation of Science Party Requirements and Technician Requirements |
The cruise would require two SIO ship techs for round the clock CTD operation, a chemist for running nutrients/O2/salts, and computer tech for data archival |
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 Dynamic Positioning |  ADCP | Multibeam | Seismic |
| Dredging/Coring/Large Dia. Trawl Wire | Stern A-frame | Fiber Optic (.681) | 0.680 Coax Wire |
| SCUBA Diving | Radioisotope use - briefly describe | NO Radioisotope use/Natural level work | Other Operator Provided Inst. - Describe |
| 0 PI-Provided Vans - briefly describe | MOCNESS | | |
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Explain Instrumentation or Capability
requirements that could affect choice
of ship in scheduling. |
a) Radioisotope use- 14C primary production/calcification work (the same that we have done aboard R/V Revelle on 4 previous cruises.
b) The trace metal work would either be done on the ship by creating a trace-metal clean "bubble" in one of the ship's labs or (preferably) using a UNOLS trace metal clean van (if one is available)
c) CTD/hydrocast capability with 30L Niskins
d) We are requesting dynamic positioning since surface current sheer is high in the region of the Subantarctic Front which can make station keeping more challenging
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Explain Major Ancillary Facilities
Requirements and list description
and provider for "other" systems. |
A trace-metal clean van will be required for Morton to collect and process trace iron samples.
A radioisotope van will be required for Balch's group for doing 14C calcification/photosynthesis work.
On our previous Revelle cruise, we used the SIO Sperry (light-duty?) deck winch for handling Kevlar line for hanging trace-metal-clean 5L Niskin-X bottles and 30L trace-metal-clean GoFLO bottles. We would need to wrap the drum with clean fabric, then wind on 1500m of the 1/4" Kevlar line. This is critical to the work so we mark "Portable Winch" here, but if SIO still has the Sperry, then we could not need the WHOI portable light-duty winch. |
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