Corrigenda: Untersuchungen zur Zirkulation in mittleren und oberen Wassermassen des Nordatlantiks mit Lagrange’schen und profilierenden Methoden

Chapter 2 of the dissertation, “Analyses of the Circulation in Intermediate and Shallow Water Masses of the North Atlantic with Lagrangian and Profiling Methods”, contains the following mistake: It says that the chapter reproduces a publication by Lankhorst, Send, and Biastoch (2007b), with a copyright notice referring to the American Geophysical Union (AGU). This is incorrect. There was an attempt to publish this with the AGU, but the manuscript was never accepted for publication there, and the AGU has no copyright to any of the materials.Kapitel 2 der Dissertation “Untersuchungen zur Zirkulation in mittleren und oberen Wassermassen des Nordatlantiks mit Lagrange’schen und profilierenden Methoden” enthält den folgenden Fehler: Es wird behauptet, das Kapitel reproduziere eine Veröffentlichung von Lankhorst, Send und Biastoch (2007b) mit einem Copyright-Bezug zur American Geophysical Union (AGU). Dies ist inkorrekt. Es hat zwar einen Versuch gegeben, dies bei der AGU zu publizieren, aber das Manuskript ist dort nie zur Veröffentlichung angenommen worden, und die AGU hat keinerlei Urheberrechte an den Inhalten

A Self-Contained Identification Scheme for Eddies in Drifter and Float Trajectories

It is becoming increasingly recognized that the eddy field plays an important—possibly dominating—role for oceanic motions in many aspects (e.g., transport of properties and risk assessment in the case of extreme events). This motivates the study of individual eddy events. In the Lagrangian coordinate system, vorticity possibly associated with eddies appears in two forms: as shear vorticity between neighboring particles, and as curvature of the trajectory of a single particle. Typical field experiments in physical oceanography using surface drifters or subsurface floats do not reach data densities high enough to produce enough encounters of drifters to calculate shear vorticity between them. However, curvature in individual tracks is easily observed. This study presents a methodology that extracts segments from within a trajectory that are “looping,” which will be interpreted as a drifter being caught in an eddy. The method makes use of autoregressive processes, a simple type of stochastic processes, which easily enables a fit to the nonperfectly shaped trajectory data usually expected from field experiments. These processes also deliver frequency and persistence of the detected eddies by a very simple calculation, which makes the methodology highly suited for automatized scanning of larger datasets

Untersuchungen zur Zirkulation in mittleren und oberen Wassermassen des Nordatlantiks mit Lagrange'schen und profilierenden Methoden

The Atlantic Meridional Overturning Circulation (MOC) transports warm water northwards in near-surface depth layers and cold water southwards at greater depths. This dissertation investigates aspects of the circulation within the context of the MOC in the northeastern and tropical Atlantic, based on observations of the past 20 years. The instrumentation mainly relies on submerged drifters called floats, which measure current velocities and, depending on instrument type, hydrographic profiles.Die meridionale Umwälzbewegung (MOC, Meridional Overturning Circulation) des Atlantiks transportiert warmes Wasser in den oberflächennahen Schichten nordwärts sowie kaltes Wasser in größeren Tiefen südwärts. Diese Dissertation untersucht vor dem Hintergrund der MOC Teilaspekte der Zirkulation im nordöstlichen sowie im tropischen Atlantik, basierend auf Beobachtungen der letzten 20 Jahre. Als Meßgeräte kommen dabei hauptsächlich Unterwasserdrifter namens Floats zum Einsatz, die Strömungsgeschwindigkeit und, je nach Typ, vertikale hydrographische Profile messen

The 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

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) 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.Funding was provided by the National Oceanic and Atmospheric Administration under Grant No. NA14OAR4320158

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

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 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.Funding was provided by the National Oceanic and Atmospheric Administration under Grant No. NA14OAR432015

Observed basin-scale response of the North Atlantic Meridional Overturning Circulation to wind stress forcing

The response of the North Atlantic Meridional Overturning Circulation (MOC) to wind stress forcing is investigated from an observational standpoint, using four time series of overturning transports below and relative to 1000 m, overlapping by 3.6 years. These time series are derived from four mooring arrays located on the western boundary of the North Atlantic: the RAPID WAVE array (42.5°N), the Woods Hole Oceanographic Institution Line W array (39°N), the RAPID MOC/MOCHA array (26.5°N), and the MOVE array (16°N). Using modal decompositions of the analytic cross-correlation between transports and wind stress, the basin-scale wind stress is shown to significantly drives the MOC coherently at four latitudes, on the timescales available for this study. The dominant mode of covariance is interpreted as rapid barotropic oceanic adjustments to wind stress forcing, eventually forming two counter-rotating Ekman overturning cells centered on the tropics and subtropical gyre. A second mode of covariance appears related to patterns of wind stress and wind stress curl associated with the North Atlantic Oscillation, spinning anomalous horizontal circulations which likely interact with topography to form overturning cells

Observation of decadal change in the Atlantic meridional overturning circulation using 10 years of continuous transport data

The meridional overturning circulation (MOC) represents the main mechanism for the oceanic northward heat transport in the Atlantic, and fluctuations of this circulation are believed to have major impacts on northern hemisphere climate. While numerical ocean and climate models and paleo-records show large variability in this circulation, the use of direct observations of the MOC for detecting climate-timescale changes has proven difficult so far. This report presents the first observational record of MOC measurements that is continuous and sufficiently long to exhibit decadal-scale changes, here a decrease by 20% over the observational period (Jan. 2000–June 2009) and large interannual changes in the flow and its vertical structure. Data are from a mooring array at 16°N (Meridional Overturning Variability Experiment, MOVE). The observed change agrees with the amplitude of multi-decadal natural fluctuations seen in numerical ocean and climate models. Knowledge of the existence and phasing of such internal cycles provides multi-decadal climate predictability. Recently, some numerical model simulations have produced results that show a weakening of the MOC since the 1990's and observational confirmation of this now is a high priority

The mid-depth circulation of the northwestern tropical Atlantic observed by floats

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 56 (2009): 1615-1632, doi:10.1016/j.dsr.2009.06.002.A 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.MOVE was funded by the Bundesministerium fu¨r Bildung und Forschung (grants 03F0246A and 03F0377B) as well as by the Deutsche Forschungsgemeinschaft (grant SE815/21), NBC by the National Science Foundation through grants OCE 97-29765 and OCE 01-36477, and SAMBA was fully supported by Ifremer