Koelling Jannes

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  • Article
    Linking oxygen and carbon uptake with the Meridional Overturning Circulation using a transport mooring array
    (Oceanography Society, 2022-01-07) Atamanchuk, Dariia ; Palter, Jaime B. ; Palevsky, Hilary I. ; Le Bras, Isabela A. ; Koelling, Jannes ; Nicholson, David P.
    The Atlantic Meridional Overturning Circulation (AMOC) is a system of ocean currents that transports warm, salty water poleward from the tropics to the North Atlantic. Its structure and strength are monitored at several latitudes by mooring arrays installed by the international ocean sciences community. While the main motivation for deploying these mooring arrays is to understand the AMOC’s influence on Northern Hemisphere climate, the circulation system also plays a crucial role in distributing oxygen (O2) and carbon dioxide (CO2) throughout the global ocean. By adding O2 sensors to several of the moorings at 53°N–60°N (Figure 1) in the western Labrador Sea, Koelling et al. (2021) demonstrated that the formation of deep water, in which the AMOC brings surface water to the deep ocean, is important for supplying the oxygen consumed by deep-ocean ecosystems throughout the North Atlantic. Additionally, variability in the deep-water formation has been linked to changes in the amount of anthropogenic CO2 stored in the subpolar ocean (Raimondi et al., 2021). These studies, using data collected during research cruises and a small number of moored sensors, showed that deep-water formation and the AMOC are key to oxygen and carbon cycles in the North Atlantic. However, the common assumption that the magnitude and variability of O2 and CO2 uptake by the ocean are tied to the dynamics of the AMOC has never been evaluated on the basis of direct observations.
  • Technical Report
    The 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, Jannes
    The 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) 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.
  • Article
    Atlantic 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.