Lankhorst
Matthias
Lankhorst
Matthias
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Book chapterGlobal Oceans [in “State of the Climate in 2020”](American Meteorological Society, 2021-08-01) Johnson, Gregory C. ; Lumpkin, Rick ; Alin, Simone R. ; Amaya, Dillon J. ; Baringer, Molly O. ; Boyer, Tim ; Brandt, Peter ; Carter, Brendan ; Cetinić, Ivona ; Chambers, Don P. ; Cheng, Lijing ; Collins, Andrew U. ; Cosca, Cathy ; Domingues, Ricardo ; Dong, Shenfu ; Feely, Richard A. ; Frajka-Williams, Eleanor E. ; Franz, Bryan A. ; Gilson, John ; Goni, Gustavo J. ; Hamlington, Benjamin D. ; Herrford, Josefine ; Hu, Zeng-Zhen ; Huang, Boyin ; Ishii, Masayoshi ; Jevrejeva, Svetlana ; Kennedy, John J. ; Kersalé, Marion ; Killick, Rachel E. ; Landschützer, Peter ; Lankhorst, Matthias ; Leuliette, Eric ; Locarnini, Ricardo ; Lyman, John ; Marra, John F. ; Meinen, Christopher S. ; Merrifield, Mark ; Mitchum, Gary ; Moat, Bengamin I. ; Nerem, R. Steven ; Perez, Renellys ; Purkey, Sarah G. ; Reagan, James ; Sanchez-Franks, Alejandra ; Scannell, Hillary A. ; Schmid, Claudia ; Scott, Joel P. ; Siegel, David A. ; Smeed, David A. ; Stackhouse, Paul W. ; Sweet, William V. ; Thompson, Philip R. ; Trinanes, Joaquin ; Volkov, Denis L. ; Wanninkhof, Rik ; Weller, Robert A. ; Wen, Caihong ; Westberry, Toby K. ; Widlansky, Matthew J. ; Wilber, Anne C. ; Yu, Lisan ; Zhang, Huai-MinThis chapter details 2020 global patterns in select observed oceanic physical, chemical, and biological variables relative to long-term climatologies, their differences between 2020 and 2019, and puts 2020 observations in the context of the historical record. In this overview we address a few of the highlights, first in haiku, then paragraph form: La Niña arrives, shifts winds, rain, heat, salt, carbon: Pacific—beyond. Global ocean conditions in 2020 reflected a transition from an El Niño in 2018–19 to a La Niña in late 2020. Pacific trade winds strengthened in 2020 relative to 2019, driving anomalously westward Pacific equatorial surface currents. Sea surface temperatures (SSTs), upper ocean heat content, and sea surface height all fell in the eastern tropical Pacific and rose in the western tropical Pacific. Efflux of carbon dioxide from ocean to atmosphere was larger than average across much of the equatorial Pacific, and both chlorophyll-a and phytoplankton carbon concentrations were elevated across the tropical Pacific. Less rain fell and more water evaporated in the western equatorial Pacific, consonant with increased sea surface salinity (SSS) there. SSS may also have increased as a result of anomalously westward surface currents advecting salty water from the east. El Niño–Southern Oscillation conditions have global ramifications that reverberate throughout the report.
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Technical ReportThe Northwest Tropical Atlantic Station (NTAS) : NTAS-15 Mooring Turnaround Cruise Report cruise on board RV Endeavor January 25 - February 13, 2016 Narragansett RI, USA - San Juan, Puerto Rico(Woods Hole Oceanographic Institution, 2016-11) Bigorre, Sebastien P. ; Ryder, James R. ; Smith, Jason C. ; Lankhorst, Matthias ; Plueddemann, AlbertThe Northwest Tropical Atlantic Station (NTAS) was established to address the need for accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface temperature anomalies and the likelihood of significant local air–sea interaction on interannual to decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 15°N, 51°W by successive mooring turnarounds. These observations are used to investigate air–sea interaction processes related to climate variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Climate Observation Program. This report documents recovery of the NTAS-14 mooring and deployment of the NTAS-15 mooring at the same site. Both moorings used Surlyn foam buoys as the surface element. These buoys were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 160 m of the mooring line were outfitted with oceanographic sensors for the measurement of temperature, salinity and velocity. The mooring turnaround was done by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution (WHOI), onboard R/V Endeavor, Cruise EN573. The cruise took place between January 25 and February 13 2016. The NTAS-15 mooring was deployed on February 2, and the NTAS-14 mooring was recovered on February 4. A 24-hour intercomparison period was conducted on February 5, during which data from the buoy, telemetered through Argos satellite system, and the ship’s meteorological and oceanographic data were monitored while the ship was stationed 0.2 nm downwind of NTAS-15 buoy. A similar procedure was done at NTAS-14 but for only about 10 hours on the morning of February 4. This report describes these operations, as well as other work done on the cruise and some of the precruise buoy preparations. Other operations during EN573 consisted in the recovery and deployment of the Meridional Overturning Variability Experiment (MOVE) subsurface moorings array (MOVE 1 in the east, and MOVE 3 and 4 in the west near Guadeloupe). Acoustic download of data from Pressure Inverted Echo Sounders (PIES) was also conducted. MOVE is designed to monitor the integrated deep meridional flow in the tropical North Atlantic.
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ArticleOn the development of SWOT in situ calibration/validation for short-wavelength ocean topography(American Meteorological Society, 2022-05-01) Wang, Jinbo ; Fu, Lee-Lueng ; Haines, Bruce ; Lankhorst, Matthias ; Lucas, Andrew J. ; Farrar, J. Thomas ; Send, Uwe ; Meinig, Christian ; Schofield, Oscar M. E. ; Ray, Richard D.The future Surface Water and Ocean Topography (SWOT) mission aims to map sea surface height (SSH) in wide swaths with an unprecedented spatial resolution and subcentimeter accuracy. The instrument performance needs to be verified using independent measurements in a process known as calibration and validation (Cal/Val). The SWOT Cal/Val needs in situ measurements that can make synoptic observations of SSH field over an O(100) km distance with an accuracy matching the SWOT requirements specified in terms of the along-track wavenumber spectrum of SSH error. No existing in situ observing system has been demonstrated to meet this challenge. A field campaign was conducted during September 2019–January 2020 to assess the potential of various instruments and platforms to meet the SWOT Cal/Val requirement. These instruments include two GPS buoys, two bottom pressure recorders (BPR), three moorings with fixed conductivity–temperature–depth (CTD) and CTD profilers, and a glider. The observations demonstrated that 1) the SSH (hydrostatic) equation can be closed with 1–3 cm RMS residual using BPR, CTD mooring and GPS SSH, and 2) using the upper-ocean steric height derived from CTD moorings enable subcentimeter accuracy in the California Current region during the 2019/20 winter. Given that the three moorings are separated at 10–20–30 km distance, the observations provide valuable information about the small-scale SSH variability associated with the ocean circulation at frequencies ranging from hourly to monthly in the region. The combined analysis sheds light on the design of the SWOT mission postlaunch Cal/Val field campaign.
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ArticleLagrangian views of the pathways of the Atlantic meridional overturning circulation(American Geophysical Union, 2019-07-19) Bower, Amy S. ; Lozier, M. Susan ; Biastoch, Arne ; Drouin, Kimberley L. ; Foukal, Nicholas P. ; Furey, Heather H. ; Lankhorst, Matthias ; Rühs, Siren ; Zou, SijiaThe Lagrangian method—where current location and intensity are determined by tracking the movement of flow along its path—is the oldest technique for measuring the ocean circulation. For centuries, mariners used compilations of ship drift data to map out the location and intensity of surface currents along major shipping routes of the global ocean. In the mid‐20th century, technological advances in electronic navigation allowed oceanographers to continuously track freely drifting surface buoys throughout the ice‐free oceans and begin to construct basin‐scale, and eventually global‐scale, maps of the surface circulation. At about the same time, development of acoustic methods to track neutrally buoyant floats below the surface led to important new discoveries regarding the deep circulation. Since then, Lagrangian observing and modeling techniques have been used to explore the structure of the general circulation and its variability throughout the global ocean, but especially in the Atlantic Ocean. In this review, Lagrangian studies that focus on pathways of the upper and lower limbs of the Atlantic Meridional Overturning Circulation (AMOC), both observational and numerical, have been gathered together to illustrate aspects of the AMOC that are uniquely captured by this technique. These include the importance of horizontal recirculation gyres and interior (as opposed to boundary) pathways, the connectivity (or lack thereof) of the AMOC across latitudes, and the role of mesoscale eddies in some regions as the primary AMOC transport mechanism. There remain vast areas of the deep ocean where there are no direct observations of the pathways of the AMOC.
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PreprintThe mid-depth circulation of the northwestern tropical Atlantic observed by floats( 2009-05-29) Lankhorst, Matthias ; Fratantoni, David M. ; Ollitrault, Michel ; Richardson, Philip L. ; Send, Uwe ; Zenk, WalterA comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e. g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7 Sv across 16° N between the Antilles islands and the Mid- Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADWeast of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow.
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ArticleASIRI : an ocean–atmosphere initiative for Bay of Bengal(American Meteorological Society, 2016-11-22) Wijesekera, Hemantha W. ; Shroyer, Emily L. ; Tandon, Amit ; Ravichandran, M. ; Sengupta, Debasis ; Jinadasa, S. U. P. ; Fernando, Harindra J. S. ; Agrawal, Neeraj ; Arulananthan, India K. ; Bhat, G. S. ; Baumgartner, Mark F. ; Buckley, Jared ; Centurioni, Luca R. ; Conry, Patrick ; Farrar, J. Thomas ; Gordon, Arnold L. ; Hormann, Verena ; Jarosz, Ewa ; Jensen, Tommy G. ; Johnston, T. M. Shaun ; Lankhorst, Matthias ; Lee, Craig M. ; Leo, Laura S. ; Lozovatsky, Iossif ; Lucas, Andrew J. ; MacKinnon, Jennifer A. ; Mahadevan, Amala ; Nash, Jonathan D. ; Omand, Melissa M. ; Pham, Hieu ; Pinkel, Robert ; Rainville, Luc ; Ramachandran, Sanjiv ; Rudnick, Daniel L. ; Sarkar, Sutanu ; Send, Uwe ; Sharma, Rashmi ; Simmons, Harper L. ; Stafford, Kathleen M. ; St. Laurent, Louis C. ; Venayagamoorthy, Subhas K. ; Venkatesan, Ramasamy ; Teague, William J. ; Wang, David W. ; Waterhouse, Amy F. ; Weller, Robert A. ; Whalen, Caitlin B.Air–Sea Interactions in the Northern Indian Ocean (ASIRI) is an international research effort (2013–17) aimed at understanding and quantifying coupled atmosphere–ocean dynamics of the Bay of Bengal (BoB) with relevance to Indian Ocean monsoons. Working collaboratively, more than 20 research institutions are acquiring field observations coupled with operational and high-resolution models to address scientific issues that have stymied the monsoon predictability. ASIRI combines new and mature observational technologies to resolve submesoscale to regional-scale currents and hydrophysical fields. These data reveal BoB’s sharp frontal features, submesoscale variability, low-salinity lenses and filaments, and shallow mixed layers, with relatively weak turbulent mixing. Observed physical features include energetic high-frequency internal waves in the southern BoB, energetic mesoscale and submesoscale features including an intrathermocline eddy in the central BoB, and a high-resolution view of the exchange along the periphery of Sri Lanka, which includes the 100-km-wide East India Coastal Current (EICC) carrying low-salinity water out of the BoB and an adjacent, broad northward flow (∼300 km wide) that carries high-salinity water into BoB during the northeast monsoon. Atmospheric boundary layer (ABL) observations during the decaying phase of the Madden–Julian oscillation (MJO) permit the study of multiscale atmospheric processes associated with non-MJO phenomena and their impacts on the marine boundary layer. Underway analyses that integrate observations and numerical simulations shed light on how air–sea interactions control the ABL and upper-ocean processes.
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Technical ReportThe Northwest Tropical Atlantic Station (NTAS) : NTAS-17 mooring turnaround cruise report cruise on board FV Pisces May 30 – June 21, 2018 Mayport, FL, USA – Morehead City, NC, USA(Woods Hole Oceanographic Institution, 2018-09) Bigorre, Sebastien P. ; Pietro, Benjamin ; Smith, Jason ; Lankhorst, Matthias ; Koelling, JannesThe Northwest Tropical Atlantic Station (NTAS) was established to address the need for accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface temperature anomalies and the likelihood of significant local air–sea interaction on interannual to decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 15N, 51W by successive mooring turnarounds. These observations are used to investigate air–sea interaction processes related to climate variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Ocean Observing and Monitoring Division. This report documents recovery of the NTAS-16 mooring and deployment of the NTAS-17 mooring at the same site. Both moorings used Surlyn foam buoys as the surface element. These buoys were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 160 m of the mooring line were outfitted with oceanographic sensors for the measurement of temperature, salinity and velocity. The mooring turnaround was done by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution (WHOI), onboard F/V Pisces, Cruise PC-18-03. The cruise took place between May 30 and June 21 2018. The NTAS-17 mooring was deployed on June 10, and the NTAS-16 mooring was recovered on June 12. No inter-comparison between ship and buoys was performed on this cruise. This report describes these operations, as well as other work done on the cruise and some of the pre-cruise buoy preparations. Other operations during PC-18-03 consisted in the recovery and deployment of the Meridional Overturning Variability Experiment (MOVE) subsurface moorings array (MOVE 1 in the east, and MOVE 3 and 4 in the west near Guadeloupe). Acoustic download of data from Pressure Inverted Echo Sounders (PIES) was also conducted. MOVE is designed to monitor the integrated deep meridional flow in the tropical North Atlantic.
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Technical ReportCALYPSO 2019 Cruise Report: field campaign in the Mediterranean(Woods Hole Oceanographic Institution, 2020-01) Mahadevan, Amala ; D'Asaro, Eric A. ; Allen, John T. ; Almaraz García, Pablo ; Alou-Font, Eva ; Aravind, Harilal Meenambika ; Balaguer, Pau ; Caballero, Isabel ; Calafat, Noemi ; Carbornero, Andrea ; Casas, Benjamin ; Castilla, Carlos ; Centurioni, Luca R. ; Conley, Margaret ; Cristofano, Gino ; Cutolo, Eugenio ; Dever, Mathieu ; Enrique Navarro, Angélica ; Falcieri, Francesco ; Freilich, Mara ; Goodwin, Evan ; Graham, Raymond ; Guigand, Cedric ; Hodges, Benjamin A. ; Huntley, Helga ; Johnston, T. M. Shaun ; Lankhorst, Matthias ; Lermusiaux, Pierre F. J. ; Lizaran, Irene ; Mirabito, Chris ; Miralles, A. ; Mourre, Baptiste ; Navarro, Gabriel ; Ohmart, Michael ; Ouala, Said ; Ozgokmen, Tamay M. ; Pascual, Ananda ; Pou, Joan Mateu Horrach ; Poulain, Pierre Marie ; Ren, Alice ; Tarry, Daniel R. ; Rudnick, Daniel L. ; Rubio, M. ; Ruiz, Simon ; Rypina, Irina I. ; Tintore, Joaquin ; Send, Uwe ; Shcherbina, Andrey Y. ; Torner, Marc ; Salvador-Vieira, Guilherme ; Wirth, Nikolaus ; Zarokanellos, NikolaosThis cruise aimed to identify transport pathways from the surface into the interior ocean during the late winter in the Alborán sea between the Strait of Gibraltar (5°40’W) and the prime meridian. Theory and previous observations indicated that these pathways likely originated at strong fronts, such as the one that separates salty Mediterranean water and the fresher water in owing from the Atlantic. Our goal was to map such pathways and quantify their transport. Since the outcropping isopycnals at the front extend to the deepest depths during the late winter, we planned the cruise at the end of the Spring, prior to the onset of thermal stratification of the surface mixed layer.
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ArticleBay of Bengal intraseasonal oscillations and the 2018 monsoon onset(American Meteorological Society, 2021-10-01) Shroyer, Emily L. ; Tandon, Amit ; Sengupta, Debasis ; Fernando, Harindra J. S. ; Lucas, Andrew J. ; Farrar, J. Thomas ; Chattopadhyay, Rajib ; de Szoeke, Simon P. ; Flatau, Maria ; Rydbeck, Adam ; Wijesekera, Hemantha W. ; McPhaden, Michael J. ; Seo, Hyodae ; Subramanian, Aneesh C. ; Venkatesan, Ramasamy ; Joseph, Jossia K. ; Ramsundaram, S. ; Gordon, Arnold L. ; Bohman, Shannon M. ; Pérez, Jaynise ; Simoes-Sousa, Iury T. ; Jayne, Steven R. ; Todd, Robert E. ; Bhat, G. S. ; Lankhorst, Matthias ; Schlosser, Tamara L. ; Adams, Katherine ; Jinadasa, S. U. P. ; Mathur, Manikandan ; Mohapatra, Mrutyunjay ; Rama Rao, E. Pattabhi ; Sahai, Atul Kumar ; Sharma, Rashmi ; Lee, Craig ; Rainville, Luc ; Cherian, Deepak A. ; Cullen, Kerstin ; Centurioni, Luca R. ; Hormann, Verena ; MacKinnon, Jennifer A. ; Send, Uwe ; Anutaliya, Arachaporn ; Waterhouse, Amy F. ; Black, Garrett S. ; Dehart, Jeremy A. ; Woods, Kaitlyn M. ; Creegan, Edward ; Levy, Gad ; Kantha, Lakshmi ; Subrahmanyam, BulusuIn the Bay of Bengal, the warm, dry boreal spring concludes with the onset of the summer monsoon and accompanying southwesterly winds, heavy rains, and variable air–sea fluxes. Here, we summarize the 2018 monsoon onset using observations collected through the multinational Monsoon Intraseasonal Oscillations in the Bay of Bengal (MISO-BoB) program between the United States, India, and Sri Lanka. MISO-BoB aims to improve understanding of monsoon intraseasonal variability, and the 2018 field effort captured the coupled air–sea response during a transition from active-to-break conditions in the central BoB. The active phase of the ∼20-day research cruise was characterized by warm sea surface temperature (SST > 30°C), cold atmospheric outflows with intermittent heavy rainfall, and increasing winds (from 2 to 15 m s−1). Accumulated rainfall exceeded 200 mm with 90% of precipitation occurring during the first week. The following break period was both dry and clear, with persistent 10–12 m s−1 wind and evaporation of 0.2 mm h−1. The evolving environmental state included a deepening ocean mixed layer (from ∼20 to 50 m), cooling SST (by ∼1°C), and warming/drying of the lower to midtroposphere. Local atmospheric development was consistent with phasing of the large-scale intraseasonal oscillation. The upper ocean stores significant heat in the BoB, enough to maintain SST above 29°C despite cooling by surface fluxes and ocean mixing. Comparison with reanalysis indicates biases in air–sea fluxes, which may be related to overly cool prescribed SST. Resolution of such biases offers a path toward improved forecasting of transition periods in the monsoon.
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Technical ReportThe Northwest Tropical Atlantic Station (NTAS): NTAS-21 Mooring Turnaround Cruise Report Cruise On Board RV Ronald H. Brown JOctober 6-25, 2022 Bridgetown, Barbados – Bridgetown, Barbados(Woods Hole Oceanographic Institution, 2022-12) Bigorre, Sebastien P. ; Graham, Raymond ; Lankhorst, MatthiasThe Northwest Tropical Atlantic Station (NTAS) was established to address the need for accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface temperature anomalies and the likelihood of significant local air–sea interaction on interannual to decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 15°N, 51°W by successive mooring turnarounds. These observations are used to investigate air–sea interaction processes related to climate variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Global Ocean Monitoring and Observing (GOMO) Program (formerly Ocean Observing and Monitoring Division). This report documents recovery of the NTAS-20, the final mooring of the NTAS time-series. The NTAS moorings use Surlyn foam buoys as the surface element. These buoys were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each system measures, records, and transmits via satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture, and momentum. The upper 160 m of the mooring line were outfitted with oceanographic sensors for the measurement of temperature, salinity, and velocity. The mooring recovery was done by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution (WHOI) and Drew Cole, onboard R/V Ronald H. Brown, Cruise RB-22-04. The cruise took place between October 6 and 25 2022. Other operations during the cruise consisted of the intercomparison between ship and NTAS buoy measurements, turnaround of Meridional Overturning Variability Experiment (MOVE) subsurface mooring array, CTD casts, and four Argo floats deployments. MOVE is designed to monitor the integrated deep meridional flow in the tropical North Atlantic. This report describes these operations.
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ArticleAtlantic meridional overturning circulation: Observed transport and variability(Frontiers Media, 2019-06-07) Frajka-Williams, Eleanor ; Ansorge, Isabelle ; Baehr, Johanna ; Bryden, Harry L. ; Chidichimo, Maria Paz ; Cunningham, Stuart A. ; Danabasoglu, Gokhan ; Dong, Shenfu ; Donohue, Kathleen A. ; Elipot, Shane ; Heimbach, Patrick ; Holliday, Naomi Penny ; Hummels, Rebecca ; Jackson, Laura C. ; Karstensen, Johannes ; Lankhorst, Matthias ; Le Bras, Isabela A. ; Lozier, M. Susan ; McDonagh, Elaine L. ; Meinen, Christopher S. ; Mercier, Herlé ; Moat, Bengamin I. ; Perez, Renellys ; Piecuch, Christopher G. ; Rhein, Monika ; Srokosz, Meric ; Trenberth, Kevin E. ; Bacon, Sheldon ; Forget, Gael ; Goni, Gustavo J. ; Kieke, Dagmar ; Koelling, Jannes ; Lamont, Tarron ; McCarthy, Gerard D. ; Mertens, Christian ; Send, Uwe ; Smeed, David A. ; Speich, Sabrina ; van den Berg, Marcel ; Volkov, Denis L. ; Wilson, Christopher G.The Atlantic Meridional Overturning Circulation (AMOC) extends from the Southern Ocean to the northern North Atlantic, transporting heat northwards throughout the South and North Atlantic, and sinking carbon and nutrients into the deep ocean. Climate models indicate that changes to the AMOC both herald and drive climate shifts. Intensive trans-basin AMOC observational systems have been put in place to continuously monitor meridional volume transport variability, and in some cases, heat, freshwater and carbon transport. These observational programs have been used to diagnose the magnitude and origins of transport variability, and to investigate impacts of variability on essential climate variables such as sea surface temperature, ocean heat content and coastal sea level. AMOC observing approaches vary between the different systems, ranging from trans-basin arrays (OSNAP, RAPID 26°N, 11°S, SAMBA 34.5°S) to arrays concentrating on western boundaries (e.g., RAPID WAVE, MOVE 16°N). In this paper, we outline the different approaches (aims, strengths and limitations) and summarize the key results to date. We also discuss alternate approaches for capturing AMOC variability including direct estimates (e.g., using sea level, bottom pressure, and hydrography from autonomous profiling floats), indirect estimates applying budgetary approaches, state estimates or ocean reanalyses, and proxies. Based on the existing observations and their results, and the potential of new observational and formal synthesis approaches, we make suggestions as to how to evaluate a comprehensive, future-proof observational network of the AMOC to deepen our understanding of the AMOC and its role in global climate.