GO-SHIP A22 2021 Hydrographic Program¶

Cruise Scientific Objectives¶

Viviane Menezes

The A22 2021 cruise aboard the UNOLS vessel R/V Thomas G. Thompson was undertaken as part of the US GO-SHIP (Global Ocean Ship-based Hydrographic Investigations Program), a major contributor to international GO-SHIP. The program’s overall objective is to collect quasi-decadal, highly accurate, surface-to-bottom, coast-to-coast, physical, and chemical oceanic observations. These measurements are essential to monitoring long-term changes in heat, freshwater, carbon, oxygen, and other tracers in the global ocean– the main reservoir in the Earth System.

The A22 meridional transect spans the western North Atlantic from the tropics to the subtropics and is the only GO-SHIP transect in the Caribbean Sea. This year, the A22 worked from South America’s continental shelf break, near Aruba, to Puerto Rico and thence northwards to Bermuda along the 66o W meridian. From Bermuda, the transect stretched to the continental shelf south of Woods Hole, following the Line W path (scienceweb.whoi.edu/linew/index.php). This is the first reoccupation of Line W after the end of that program in 2014, whose objective was monitoring the deep limb of the Atlantic Meridional Overturning Circulation (AMOC).

Along the way, the A22 transect crossed major western boundary currents systems: the Caribbean Current, the Gulf Stream, and the North Atlantic Deep Western Boundary Current (DWBC) at different latitudes. The latter two are primary conduits of the AMOC.

Although the A22 transect has been slightly modified over the years, this was the fourth reoccupation of this line in the last three decades. The A22 was first occupied in 1997 (79 stations; R/V Knorr) during WOCE (World Ocean Circulation Experiment), then in 2003 (82 stations; R/V Knorr) and 2012 (81 stations; R/V Atlantis) as part of the CLIVAR (Climate Variability and Predictability).

In 2021, 90 CTD/LADCP/rosette stations were performed over the course of 27-days during boreal spring (20 April - 16 May 2021). Stations were nominally spaced by about 30 nm (50 km) in the open-ocean but closer (<= 15 nm) at boundary currents and major topographic features. At each station, a suite of surface to bottom vertical profiles was collected using electronic sensors (CTDO, LADCPS, chi-pods, transmissometer, UVP (Underwater Vision Profile)), and 36 Niskin bottles for sampling water at discrete vertical levels.

Data collected during the A22 2021 were (some samplings will be processed in labs onshore):

Pressure, temperature, salinity, dissolved oxygen
Fluorescence, shear and micro-scale temperature
Current velocities from lowered and shipboard ADCPs
Major nutrients (silicate, phosphate, nitrate, nitrite)
Transient tracers (Chlorofluorocarbons (CFC-11 and 12), Sulphur Hexafluoride (SF₆) and Nitrous Oxide (N₂O))
Carbon components: total dissolved inorganic carbon (DIC), total alkalinity, pH, and partial pressure of CO₂, dissolved organic carbon (DOC), total dissolved nitrogen (TDN)
Nitrate isotopes and radiocarbons
HPLC pigments and particulate organic carbon (POC)
Sargassum seaweed
Bathymetry and shipboard meteorological observations
UVP high-resolution digital images to study large (>100 µm) particles and zooplankton
Size-fractioned microbial respiration
$\delta$ ¹⁸O (ratio of stable isotopes oxygen-18 and oxygen-16) and $\delta$ D (Deuterium) for studying the hydrological cycle

In addition to the above measurements, during the A22 8 Argo (Core), 4 Go-BGC and 2 RAFOS floats, and 19 solar-powered spotter buoys (measuring wave, wind, and sea surface temperature) were deployed.

Programs and Principal Investigators¶

Program	Affiliation	Principal Investigator	Email
CTDO Data, Salinity, Nutrients, Dissolved O₂	UCSD, SIO	Susan Becker, Jim Swift	sbecker@ucsd.edu, jswift@ucsd.edu
Total CO₂ (DIC)	AOML, PMEL, NOAA	Richard Feely, Rik Wanninkhof	richard.a.feely@noaa.gov, Rik.Wanninkhof@noaa.gov
Underway Temperature, Salinity, and pCO₂	PMEL, NOAA	Simone Alin	simone.r.alin@noaa.gov
Total Alkalinity, pH	SIO, RSMAS	Andrew Dickson, Frank Millero	adickson@ucsd.edu, fmillero@rsmas.miami.edu
Discrete pCO₂	PMEL, NOAA	Rik Wanninkhof	Rik.Wanninkhof@noaa.gov
SADCP	UH	Eric Firing	efiring@soest.hawaii.edu
LADCP	LDEO	Andreas Thurnherr	ant@ldeo.columbia.edu
CFCs, SF6, N2O	UW	Mark Warner	warner@u.washington.edu
DOC, TDN	UCSB	Craig Carlson	craig_carlson@ucsb.edu
C13 & C14	UW, WHOI	Rolf Sonnerup, Roberta Hansman	rolf@uw.edu, rhansman@whoi.edu
Transmissometry	TAMU	Wilf Gardner	wgardner@ocean.tamu.edu
Chipod	OSU	Jonathan Nash	nash@coas.oregonstate.edu
Argo Floats	WHOI	Susan Wijffels, Steven Jayne, Pelle Robbins	swijffels@whoi.edu, sjayne@whoi.edu, probbins@whoi.edu.
BGC Floats	MBARI, UW, Princeton, SIO, WHOI	Kenneth Johnson, Steven Riser, Jorge Sarmiento, Lynne Talley, Susan Wijffels	johnson@mbari.org, riser@uw.edu, jls@princeton.edu, ltalley@ucsd.edu, swijffels@whoi.edu
RAFOS Floats	WHOI	Viviane Menezes	vmenezes@whoi.edu
Canadian Arvor Floats	DFO-MPO	Clark Richards	Clark.Richards@dfo-mpo.gc.ca
Nitrate isotopes	Princeton	Daniel Sigman	sigman@princeton.edu
Oxygen isotopes	UArizona	Kaustubh Thirumalai	kaustubh@email.arizona.edu
UVP	UAF	Andrew McDonnell	amcdonnell@alaska.edu
Spotter drifters	Sofar Ocean	Cameron Dunning	cameron@sofarocean.com
Sargassum	WHOI	Dennis McGillicuddy	dmcgillicuddy@whoi.edu

Science Team and Responsibilities¶

Duty	Name	Affiliation	Email Address
Chief Scientist	Viviane Menezes	WHOI	vmenezes@whoi.edu
Co-Chief Scientist	Jesse Anderson	WHOI	jessea785@gmail.com
CTD Watchstander	Holly Olivarez	CU Boulder	holly.olivarez@colorado.edu
CTD Watchstander	Maya Prabhakar	UArizona	mayaprabhakar@email.arizona.edu
CTD Watchstander	Victoria Schoenwald	U Miami	vks16@rsmas.miami.edu
LADCP, CTD Watchstander	Ali Siddiqui	JHU	asiddi24@jhu.edu
Nutrients, ODF supervisor, SOCCOM floats	Susan Becker	UCSD ODF	sbecker@ucsd.edu
Nutrients	Alexandra Fine	NOAA	alexandra.fine@noaa.gov
CTDO Processing	Michael Kovatch	UCSD ODF	mkovatch@ucsd.edu
Salts, ET, CTD/Rosette Maintenance	John Calderwood	UCSD SEG	jcalderwood@ucsd.edu
Salts, CTD/Rosette Maintenance	Caitlyn Webster	UCSD STS	cwebster@ucsd.edu
Dissolved O₂, Database Management	Andrew Barna	UCSD ODF	abarna@ucsd.edu
Dissolved O₂	Robert Freiberger	UCSD	rfreiberger@ucsd.edu
UVP	Stephane O’Daly	UAF	shodaly2@alaska.edu
DIC, underway pCO2	Andrew Collins	UW	andrew.collins@noaa.gov
pCO2	Patrick Mears	U Miami	patrick.mears@noaa.gov
DIC	Charles Featherstone	NOAA	charles.featherstone@noaa.gov
CFCs, SF6	Mark Warner	UW	warner@u.washington.edu
CFCs, SF6	Bonnie Chang	UW	bxc@uw.edu
CFCs, SF6 student	Lillian Henderson	U Miami	lch39@miami.edu
pH, Total Alkalinity	Sidney Wayne	HPU	sidneyelisawayne@gmail.com
pH, Total Alkalinity	Daniela Nestory	UCSD	dnestory@ucsd.edu
pH, Total Alkalinity	Carmen Rodriguez	U Miami	crodriguez@rsmas.miami.edu
pH, Total Alkalinity	Albert Ortiz	U Miami	albert.ortiz@rsmas.miami.edu
DOC, TDN	Chance English	UCSB	cje@ucsb.edu
Marine Technician	Stephen Jalickee	UW	jalickee@uw.edu
Marine Technician	Elizabeth Ricci	UW	ericci@uw.edu