Plueddemann Albert J.

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Plueddemann

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Albert J.

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0000-0003-0228-9795

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Upper ocean momentum balances in the western equatorial Pacific on the intraseasonal time scale

( 2004-12-15) Feng, Ming ; Lukas, Roger ; Hacker, Peter ; Plueddemann, Albert J. ; Weller, Robert A.

Surface Meteorology, upper ocean current, and hydrographic measurements, collected along a repeated survey pattern and from a central mooring in the western equatorial Pacific during late 1992 to early 1993, were used to analyse upper ocean momentum balances on the intraseasonal time scale. Wind stresses derived from meteorological measurements were compared with numerical weather prediction products. Advection terms in the momentum equations were estimated by planar fits to the current and hydrographic data. Pressure gradient terms were derived from planar fits to the dynamic heights calculated from the hydrographic data, referenced by balancing the momentum equation in a selected layer below the mixed layer. Under prevailing westerly winds, westward pressure gradient forcings of 2x10-7 m s-2 were set up in the western equatorial Pacific, countering the surface wind, while the total advection tended to accelerate the eastward momentum in the surface layer. During both calm wind and westerly wind burst periods, zonal turbulent momentum fluxes estimated from the ocean budgets were comparable with those estimated from microstructure dissipation rate measurements and with zonal wind stresses, so that the zonal momentum could be balanced within error bars. The meridional momentum balances were noisier, which might be due to the fact that the short meridional length scale of the equatorial inertial-gravity waves could contaminate the dynamic signals in the mixed temporal/spatial sampling data, so that the meridional gradient estimates from the planar fits could be biased.
Wind-driven modification of the Alaskan coastal current

(American Geophysical Union, 2012-03-20) Shroyer, Emily L. ; Plueddemann, Albert J.

Across-shelf transects over the eastern flank of Barrow Canyon were obtained in August 2005 with an autonomous underwater vehicle (AUV). Here, the shelf topography creates a “choke” point in which a substantial portion of Pacific inflow from the Bering Strait is concentrated within 30 km of the coast, providing an ideal setup for monitoring the flow with the AUV. Four transects, extending ∼10 km offshore of Barrow, Alaska, inshore of the ∼80 m isobath, were used in conjunction with a process-oriented numerical model to diagnose the wind-driven modification of the Alaskan coastal current. Poleward transports of 0.12 Sv were consistent among all sections, although the transport-weighted temperature was about 1°C colder in the transect obtained during peak winds. An idealized numerical model reproduces the observed hydrographic structure and across-shelf circulation reasonably well in that (1) winds were not sufficient to reverse the poleward flow, (2) upwelling was most pronounced in the nearshore, and (3) the onshore return flow occurred throughout the interior as opposed to the bottom boundary layer. The across-shelf circulation provides a possible mechanism for a meltwater intrusion observed on the offshore side of the AUV transect made during peak winds. Also of interest is that the observed anticyclonic shear was much stronger (∣∂u/∂y∣ > f) than previously measured in the region.
Measurements of momentum and heat transfer across the air–sea interface

(American Meteorological Society, 2008-05) Gerbi, Gregory P. ; Trowbridge, John H. ; Edson, James B. ; Plueddemann, Albert J. ; Terray, Eugene A. ; Fredericks, Janet J.

This study makes direct measurements of turbulent fluxes in the mixed layer in order to close heat and momentum budgets across the air–sea interface and to assess the ability of rigid-boundary turbulence models to predict mean vertical gradients beneath the ocean’s wavy surface. Observations were made at 20 Hz at nominal depths of 2.2 and 1.7 m in 16 m of water. A new method is developed to estimate the fluxes and the length scales of dominant flux-carrying eddies from cospectra at frequencies below the wave band. The results are compared to independent estimates of those quantities, with good agreement between the two sets of estimates. The observed temperature gradients were smaller than predicted by standard rigid-boundary closure models, consistent with the suggestion that wave breaking and Langmuir circulation increase turbulent diffusivity in the upper ocean. Similarly, the Monin–Obukhov stability function ϕh was smaller in the authors’ measurements than the stability functions used in rigid-boundary applications of the Monin–Obukhov similarity theory. The dominant horizontal length scales of flux-carrying turbulent eddies were found to be consistent with observations in the bottom boundary layer of the atmosphere and from laboratory experiments in three ways: 1) in statically unstable conditions, the eddy sizes scaled linearly with distance to the boundary; 2) in statically stable conditions, length scales decreased with increasing downward buoyancy flux; and 3) downwind length scales were larger than crosswind length scales.
Corrigendum : On the exchange of momentum over the open ocean

(American Meteorological Society, 2014-09) Edson, James B. ; Jampana, Venkata ; Weller, Robert A. ; Bigorre, Sebastien P. ; Plueddemann, Albert J. ; Fairall, Christopher W. ; Miller, Scott D. ; Mahrt, Larry ; Vickers, Dean ; Hersbach, Hans
Rapid mixed layer depening by the combination of Langmuir and shear instabilities : a case study

(American Meteorological Society, 2010-11) Kukulka, Tobias ; Plueddemann, Albert J. ; Trowbridge, John H. ; Sullivan, Peter P.

Langmuir circulation (LC) is a turbulent upper-ocean process driven by wind and surface waves that contributes significantly to the transport of momentum, heat, and mass in the oceanic surface layer. The authors have previously performed a direct comparison of large-eddy simulations and observations of the upper-ocean response to a wind event with rapid mixed layer deepening. The evolution of simulated crosswind velocity variance and spatial scales, as well as mixed layer deepening, was only consistent with observations if LC effects are included in the model. Based on an analysis of these validated simulations, in this study the fundamental differences in mixing between purely shear-driven turbulence and turbulence with LC are identified. In the former case, turbulent kinetic energy (TKE) production due to shear instabilities is largest near the surface, gradually decreasing to zero near the base of the mixed layer. This stands in contrast to the LC case in which at middepth range TKE production can be dominated by Stokes drift shear. Furthermore, the Eulerian mean vertical shear peaks near the base of the mixed layer so that TKE production by mean shear flow is elevated there. LC transports horizontal momentum efficiently downward leading to an along-wind velocity jet below LC downwelling regions at the base of the mixed layer. Locally enhanced vertical shear instabilities as a result of this jet efficiently erode the thermocline. In turn, enhanced breaking internal waves inject cold deep water into the mixed layer, where LC currents transport temperature perturbation advectively. Thus, LC and locally generated shear instabilities work intimately together to facilitate strongly the mixed layer deepening process.
Collection and processing of shipboard ADCP velocities from the Barents Sea Polar Front Experiment

(Woods Hole Oceanographic Institution, 1995-01) Harris, Carolyn L. ; Plueddemann, Albert J. ; Bourke, Robert H. ; Stone, Marla D. ; Pawlowicz, Richard A.

The Barents Sea Polar Front Experiment was a combined physical oceanography and acoustic tomography field study which took place from 6-26 August 1992. Both shipboard and moored data were collected in a 80 x 70 km experimental region on the south flank of Sptisbergen Bank about 60 km east of Bear Island. Of principal interest in this report are the data from an Acoustic Doppler Current Profier (ADCP) which was operated continuously during the experimental period as a part of the shipboard instrumentation aboard the USNS Barlett. The data from eight current meters deployed on three moorings in the experimental region are used to supplement the ADCP analysis. Preliminary results showed that velocities in the experimental region were dominated by semi-diurnal tides. The strong tidal oscilations dictated the use of a tide removal scheme to extract a steady flow component from the space-time grid of ADCP velocities. This report describes the configuration and operation of the ADCP, the space-time sampling grid on which the data were collected, the determination of absolute velocity from the ADCP measurements, and the application and results of a tide removal technique which allowed estimation of the sub-tidal flow.
Eddies in the Canada Basin, Arctic Ocean, observed from ice-tethered profilers

(American Meteorological Society, 2008-01) Timmermans, Mary-Louise ; Toole, John M. ; Proshutinsky, Andrey ; Krishfield, Richard A. ; Plueddemann, Albert J.

Five ice-tethered profilers (ITPs), deployed between 2004 and 2006, have provided detailed potential temperature θ and salinity S profiles from 21 anticyclonic eddy encounters in the central Canada Basin of the Arctic Ocean. The 12–35-m-thick eddies have center depths between 42 and 69 m in the Arctic halocline, and are shallower and less dense than the majority of eddies observed previously in the central Canada Basin. They are characterized by anomalously cold θ and low stratification, and have horizontal scales on the order of, or less than, the Rossby radius of deformation (about 10 km). Maximum azimuthal speeds estimated from dynamic heights (assuming cyclogeostrophic balance) are between 9 and 26 cm s−1, an order of magnitude larger than typical ambient flow speeds in the central basin. Eddy θ–S and potential vorticity properties, as well as horizontal and vertical scales, are consistent with their formation by instability of a surface front at about 80°N that appears in historical CTD and expendable CTD (XCTD) measurements. This would suggest eddy lifetimes longer than 6 months. While the baroclinic instability of boundary currents cannot be ruled out as a generation mechanism, it is less likely since deeper eddies that would originate from the deeper-reaching boundary flows are not observed in the survey region.
Measurements from the RV Ronald H. Brown and related platforms as part of the Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC)

(Copernicus Publications, 2021-04-29) Quinn, Patricia K. ; Thompson, Elizabeth ; Coffman, Derek J. ; Baidar, Sunil ; Bariteau, Ludovic ; Bates, Timothy S. ; Bigorre, Sebastien P. ; Brewer, Alan ; de Boer, Gijs ; de Szoeke, Simon P. ; Drushka, Kyla ; Foltz, Gregory R. ; Intrieri, Janet ; Iyer, Suneil ; Fairall, Christopher W. ; Gaston, Cassandra J. ; Jansen, Friedhelm ; Johnson, James E. ; Krüger, Ovid O. ; Marchbanks, Richard D. ; Moran, Kenneth P. ; Noone, David ; Pezoa, Sergio ; Pincus, Robert ; Plueddemann, Albert J. ; Pöhlker, Mira L. ; Pöschl, Ulrich ; Quinones Melendez, Estefania ; Royer, Haley M. ; Szczodrak, Malgorzata ; Thomson, Jim ; Upchurch, Lucia M. ; Zhang, Chidong ; Zhang, Dongxiao ; Zuidema, Paquita

The Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) took place from 7 January to 11 July 2020 in the tropical North Atlantic between the eastern edge of Barbados and 51∘ W, the longitude of the Northwest Tropical Atlantic Station (NTAS) mooring. Measurements were made to gather information on shallow atmospheric convection, the effects of aerosols and clouds on the ocean surface energy budget, and mesoscale oceanic processes. Multiple platforms were deployed during ATOMIC including the NOAA RV Ronald H. Brown (RHB) (7 January to 13 February) and WP-3D Orion (P-3) aircraft (17 January to 10 February), the University of Colorado's Robust Autonomous Aerial Vehicle-Endurant Nimble (RAAVEN) uncrewed aerial system (UAS) (24 January to 15 February), NOAA- and NASA-sponsored Saildrones (12 January to 11 July), and Surface Velocity Program Salinity (SVPS) surface ocean drifters (23 January to 29 April). The RV Ronald H. Brown conducted in situ and remote sensing measurements of oceanic and atmospheric properties with an emphasis on mesoscale oceanic–atmospheric coupling and aerosol–cloud interactions. In addition, the ship served as a launching pad for Wave Gliders, Surface Wave Instrument Floats with Tracking (SWIFTs), and radiosondes. Details of measurements made from the RV Ronald H. Brown, ship-deployed assets, and other platforms closely coordinated with the ship during ATOMIC are provided here. These platforms include Saildrone 1064 and the RAAVEN UAS as well as the Barbados Cloud Observatory (BCO) and Barbados Atmospheric Chemistry Observatory (BACO). Inter-platform comparisons are presented to assess consistency in the data sets. Data sets from the RV Ronald H. Brown and deployed assets have been quality controlled and are publicly available at NOAA's National Centers for Environmental Information (NCEI) data archive (https://www.ncei.noaa.gov/archive/accession/ATOMIC-2020, last access: 2 April 2021). Point-of-contact information and links to individual data sets with digital object identifiers (DOIs) are provided herein.
WHOI Hawaii Ocean Timeseries Station (WHOTS) : WHOTS-4 2007 mooring turnaround cruise report

(Woods Hole Oceanographic Institution, 2008-01) Whelan, Sean P. ; Plueddemann, Albert J. ; Lukas, Roger ; Lord, Jeffrey ; Lethaby, Paul ; Snyder, Jefrey ; Smith, Jason C. ; Bahr, Frank B. ; Galbraith, Nancy R. ; Sabine, Christopher L.

The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a coordinated part of the HOT program, contributing to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 22.75°N, 158°W by successive mooring turnarounds. These observations will be used to investigate air–sea interaction processes related to climate variability. The first three WHOTS moorings (WHOTS-1 through 3) were deployed in August 2004, July 2005 and June 2006, respectively. This report documents recovery of the WHOTS-3 mooring and deployment of the fourth mooring (WHOTS-4). Both moorings used Surlyn foam buoys as the surface element and were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each ASIMET 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 155 m of the moorings were outfitted with oceanographic sensors for the measurement of temperature, conductivity and velocity in a cooperative effort with R. Lukas of the University of Hawaii. A pCO2 system was installed on the WHOT-3 buoy in a cooperative effort with Chris Sabine at the Pacific Marine Environmental Laboratory. The WHOTS mooring turnaround was done on the University of Hawaii research vessel Kilo Moana, Cruise KM-07-08, by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution. The cruise took place between 24 June and 1 July 2007. Operations began with deployment of the WHOTS-4 mooring on 25 June at approximately 22°40.2′N, 157°57.0′W in 4756 m of water. This was followed by meteorological intercomparisons and CTDs at the WHOTS-4 and WHOTS-3 sites. The WHOTS-3 mooring was recovered on June 28th followed by CTD operations at the HOT site and shipboard meteorological observations at several sites to the south of the mooring site. This report describes these cruise operations, as well as some of the in-port operations and pre-cruise buoy preparations.
Phytoplankton bloom phenomena in the North Atlantic Ocean and Arabian Sea

( 2014-12) Marra, John F. ; Dickey, Thomas D. ; Plueddemann, Albert J. ; Weller, Robert A. ; Kinkade, Christopher S. ; Stramska, Malgorzata

We review bio-optical and physical data from three mooring experiments, the Marine Light–Mixed Layers programme in spring 1989 and 1991 in the Iceland Basin (59°N/21°W), and the Forced Upper Ocean Dynamics Experiment in the central Arabian Sea from October 1994 to 1995 (15.5°N/61.5°E). In the Iceland Basin, from mid-April to mid-June in 1989, chlorophyll-a concentrations are sensitive to small changes in stratification, with intermittent increases early in the record. The spring increase occurs after 20 May, coincident with persistent water column stratification. In 1991, the bloom occurs 2 weeks earlier than in 1989, with a background of strong short-term and diurnal variability in mixed layer depth and minimal horizontal advection. In the Arabian Sea, the mixing response to the northeast and southwest monsoons, plus the response to mesoscale eddies, produces four blooms over the annual cycle. The mixed layer depth in the Arabian Sea never exceeds the euphotic zone, allowing interactions between phytoplankton and grazer populations to become important. For all three mooring experiments, change in water column stratification is key in producing phytoplankton blooms.
Chalk-Ex—fate of CaCO3 particles in the mixed layer : evolution of patch optical properties

(American Geophysical Union, 2009-07-18) Balch, William M. ; Plueddemann, Albert J. ; Bowler, Bruce C. ; Drapeau, David T.

The fate of particles in the mixed layer is of great relevance to the global carbon cycle as well as to the propagation of light in the sea. We conducted four manipulative field experiments called “Chalk-Ex” in which known quantities of uniform, calcium carbonate particles were injected into the surface mixed layer. Since the production term for these patches was known to high precision, the experimental design allowed us to focus on terms associated with particle loss. The mass of chalk in the patches was evaluated using the well-calibrated light-scattering properties of the chalk plus measurements from a variety of optical measurements and platforms. Patches were surveyed with a temporal resolution of hours over spatial scales of tens of kilometers. Our results demonstrated exponential loss of the chalk particles with time from the patches. There was little evidence for rapid sinking of the chalk. Instead, horizontal eddy diffusion appeared to be the major factor affecting the dispersion of the chalk to concentrations below the limits of detection. There was unequivocal evidence of subduction of the chalk along isopycnals and subsequent formation of thin layers. Shear dispersion is the most likely mechanism to explain these results. Calculations of horizontal eddy diffusivity were consistent with other mixed layer patch experiments. Our results provide insight into the importance of physics in the formation of subsurface particle maxima in the sea, as well as the importance of rapid coccolith production and critical patch size for maintenance of natural coccolithophore blooms in nature.
Significance of Langmuir circulation in upper ocean mixing : comparison of observations and simulations

(American Geophysical Union, 2009-05-28) Kukulka, Tobias ; Plueddemann, Albert J. ; Trowbridge, John H. ; Sullivan, Peter P.

Representing upper ocean turbulence accurately in models remains a great challenge for improving weather and climate projections. Langmuir circulation (LC) is a turbulent process driven by wind and surface waves that plays a key role in transferring momentum, heat, and mass in the oceanic surface layer. We present a direct comparison between observations and large eddy simulations, based on the wave-averaged Navier-Stokes equation, of an LC growth event. The evolution of cross-wind velocity variance and spatial scales, as well as mixed layer deepening are only consistent with simulations if LC effects are included in the model. Our results offer a validation of the large eddy simulation approach to understanding LC dynamics, and demonstrate the importance of LC in ocean surface layer mixing.
Extracting wind sea and swell from directional wave spectra derived from a bottom-mounted ADCP

(Woods Hole Oceanographic Institution, 2006-07) Churchill, James H. ; Plueddemann, Albert J. ; Faluotico, Stephen M.

Recent advances in processing velocity data from bottom-mounted Acoustic Doppler Current Profilers (ADCPs) offer the capability of partitioning directional wave specctra of surface wave height in order to separate locally generated wind waves from swell. In the study described here, we have partitioned directional wavee spectra, derived from bottom-mounted ADCP measurements at the Martha’s Vineyard Coastal Observatory (MVCO) south of Martha’s Vineyard, MA, into dominant swell and locally generated wind-wave components. The partitioning was carried out following the method of Hanson and Phillips (2001) using an exploratory approach. As part of tthis approach, we assessed the validity of the ADCP-derived wave spectra by comparing them with one-dimensional wavee spectra derived from laser altimeter measurements. This comparison identified a frequency range over which the ADCP-derived wave field may be suspeect. We also carried out a series of sensitivity tests in which we evaluated how the results of wave partitioning according to the Hanson and Phillips (2001) method is influenced by varying the parameters required to implement the method. In this report, we describe and assess the data sources used in our study, outline the methods employed for wave spectra partitioning and describe partitioning results.
Hawaii coastal seawater CO2 network: A statistical evaluation of a decade of observations on tropical coral reefs.

(Frontiers Media, 2019-05-07) Terlouw, Gerianne J. ; Knor, Lucie A. C. M. ; De Carlo, Eric H. ; Drupp, Patrick S. ; Mackenzie, Fred T. ; Li, Yuan Hui ; Sutton, Adrienne J. ; Plueddemann, Albert J. ; Sabine, Christopher L.

A statistical evaluation of nearly 10 years of high-resolution surface seawater carbon dioxide partial pressure (pCO2) time-series data collected from coastal moorings around O’ahu, Hawai’i suggest that these coral reef ecosystems were largely a net source of CO2 to the atmosphere between 2008 and 2016. The largest air-sea flux (1.24 ± 0.33 mol m−2 yr−1) and the largest variability in seawater pCO2 (950 μatm overall range or 8x the open ocean range) were observed at the CRIMP-2 site, near a shallow barrier coral reef system in Kaneohe Bay O’ahu. Two south shore sites, Kilo Nalu and Ala Wai, also exhibited about twice the surface water pCO2 variability of the open ocean, but had net fluxes that were much closer to the open ocean than the strongly calcifying system at CRIMP-2. All mooring sites showed the opposite seasonal cycle from the atmosphere, with the highest values in the summer and lower values in the winter. Average coastal diurnal variabilities ranged from a high of 192 μatm/day to a low of 32 μatm/day at the CRIMP-2 and Kilo Nalu sites, respectively, which is one to two orders of magnitude greater than observed at the open ocean site. Here we examine the modes and drivers of variability at the different coastal sites. Although daily to seasonal variations in pCO2 and air-sea CO2 fluxes are strongly affected by localized processes, basin-scale climate oscillations also affect the variability on interannual time scales.
Northwest Tropical Atlantic Station (NTAS) : velocity data report for deployments 1 to 5

(Woods Hole Oceanographic Institution, 2012-09) Duncombe Rae, Chris M. ; Plueddemann, Albert J.

This report presents velocity data from the Northwest Tropical Atlantic Station (NTAS) deployments 1 through 5, from March 30, 2001, to February 28, 2006. The NTAS project has maintained a series of moorings near 14°50'N, 51°00'W in the northwest tropical Atlantic for air-sea flux measurement. The moorings include a surface buoy outfitted with Air- Sea Interaction Meteorology (ASIMET) systems for determination of bulk air-sea fluxes and oceanographic sensors along the upper 120 m of the mooring line. This report describes and presents the velocity data recovered from current meters and Acoustic Doppler Current Profilers (ADCPs) during the first five years of the NTAS project.
Comparison of direct covariance flux measurements from an offshore tower and a buoy

(American Meteorological Society, 2016-04-20) Flügge, Martin ; Bakhoday Paskyabi, Mostafa ; Reuder, Joachim ; Edson, James B. ; Plueddemann, Albert J.

Direct covariance flux (DCF) measurements taken from floating platforms are contaminated by wave-induced platform motions that need to be removed before computation of the turbulent fluxes. Several correction algorithms have been developed and successfully applied in earlier studies from research vessels and, most recently, by the use of moored buoys. The validation of those correction algorithms has so far been limited to short-duration comparisons against other floating platforms. Although these comparisons show in general a good agreement, there is still a lack of a rigorous validation of the method, required to understand the strengths and weaknesses of the existing motion-correction algorithms. This paper attempts to provide such a validation by a comparison of flux estimates from two DCF systems, one mounted on a moored buoy and one on the Air–Sea Interaction Tower (ASIT) at the Martha’s Vineyard Coastal Observatory, Massachusetts. The ASIT was specifically designed to minimize flow distortion over a wide range of wind directions from the open ocean for flux measurements. The flow measurements from the buoy system are corrected for wave-induced platform motions before computation of the turbulent heat and momentum fluxes. Flux estimates and cospectra of the corrected buoy data are found to be in very good agreement with those obtained from the ASIT. The comparison is also used to optimize the filter constants used in the motion-correction algorithm. The quantitative agreement between the buoy data and the ASIT demonstrates that the DCF method is applicable for turbulence measurements from small moving platforms, such as buoys.
The Arctic Environmental Drifting Buoy (AEDB) : report of field operations and results, August, 1987 - April 1988

(Woods Hole Oceanographic Institution, 1990-01) Honjo, Susumu ; Krishfield, Richard A. ; Plueddemann, Albert J.

There are strong reasons to gather data on polar oceanogrphy and climatology in real time using fully automated, unattended instrumentation systems for long periods; particularly during the inaccessible winter months when moving ice is extremely hazardous. We deployed an Artic Environmental Drifting Buoy (AEDB) on 4 August 1987 at 86°7'N, 22°3'E off of the FS Polarstern on a large 3.7 m thick ice island. The AEDB consisted of 2 major components: a 147 cm diameter surface float housing ARGOS transmitters and a data logger for ice-profiling thermistors, and a 125 m long mooring line attached to the sphere and fed though a 1m diameter ice hole. Along the mooring were deployed 2 fluorometers, conductivity and temperature loggers, an Acoustic Doppler Current Profiler (ADCP), a current meter, and a time-series sediment trap/micro-filter pump/transmissometer unit. The AEDB proceeded southwesterly with the Transpolar Drift at an average speed of 15.3 km/day, with a maximum speed of 88.8 km/day. On 2 January 1988, the AEDB dropped into the water while passing through the Fram Strait and for the remaining drift period was either free-floating on the water surface or underneath the sea ice. Throughout this period, the transmitters onboard successfully transmitted position, temperature, and strain caused by ice on the sphere. Although the sediment trap package was lost during the drift, valuable data was collected by the other instruments throughout the experiment. The ice thermistor data was used to determine oceanic heat flux, while continuous ADCP observations over the Yermak Plateau provided a wealth of information for understanding internal waves in the ice-covered ocean. The buoy was recovered by the Icelandic ship R/S Arni Fridriksson on 15 April 1988 at 65°17'N, 31°38'W, off southeatern Greenland, completing 3,900km of drift in 255 days. We are in the process of constructing the next automated stations which are planned for deployment in both the north and south polar regions in 1991-92.
The Ocean Observatories Initiative

(Frontiers Media, 2019-03-04) Trowbridge, John H. ; Weller, Robert A. ; Kelley, Deborah S. ; Dever, Edward P. ; Plueddemann, Albert J. ; Barth, John A. ; Kawka, Orest

The Ocean Observatories Initiative (OOI) is an integrated network that enables scientific investigation of interlinked physical, chemical, biological and geological processes throughout the global ocean. With near real-time data delivery via a common Cyberinfrastructure, the OOI instruments two contrasting ocean systems at three scales. The Regional Cabled Array instruments a tectonic plate and overlying ocean in the northeast Pacific, providing a permanent electro-optical cable connecting multiple seafloor nodes that provide high power and bandwidth to seafloor sensors and moorings with instrumented wire crawlers, all with speed-of-light interactive capabilities. Coastal arrays include the Pioneer Array, a relocatable system currently quantifying the New England shelf-break front, and the Endurance Array, a fixed system off Washington and Oregon with connections to the Regional Cabled Array. The Global Arrays host deep-ocean moorings and gliders to provide interdisciplinary measurements of the water column, mesoscale variability, and air-sea fluxes at critical high latitude locations. The OOI has unique aspects relevant to the international ocean observing community. The OOI uses common sensor types, verification protocols, and data formats across multiple platform types in diverse oceanographic regimes. OOI observing is sustained, with initial deployment in 2013 and 25 years of operation planned. The OOI is distributed among sites selected for scientific relevance based on community input and linked by important oceanographic processes. Scientific highlights include real-time observations of a submarine volcanic eruption, time-series observations of methane bubble plumes from Southern Hydrate Ridge off Oregon, observations of anomalous low-salinity pulses off Oregon, discovery of new mechanisms for intrusions of the Gulf Stream onto the shelf in the Middle Atlantic Bight, documentation of deep winter convection in the Irminger Sea, and observations of extreme surface forcing at the most southerly surface mooring in the world ocean.
Scientific rationale and conceptual design of a process-oriented shelfbreak observatory: the OOI pioneer array

(Taylor & Francis, 2019-10-23) Gawarkiewicz, Glen G. ; Plueddemann, Albert J.

The Ocean Observatories Initiative (OOI) of the National Science Foundation in the USA includes a coastal observatory called the OOI Pioneer Array, which is focused on understanding shelf/slope exchange processes. The OOI Pioneer Array has been designed and constructed and is currently in operation. In order to fully understand the design principles and constraints, we first describe the basic exchange processes and review prior experiments in the region. Emphasis is placed on the space and time scales of important exchange processes such as frontal meandering and warm core ring interactions with the Shelfbreak Front, the dominant sources of variability in the region. The three major components of the Pioneer Array are then described, including preliminary data from the underwater gliders and Autonomous Underwater Vehicle (AUV) deployments. The relevance of the Pioneer Array to important recent scientific issues in the area, including enhanced warming of the continental shelf and increasing frequency and spatial extent of Gulf Stream interactions with the continental shelf is discussed. Finally, similar observatories in Asia are briefly described, and general conclusions regarding principles that should guide the design of shelfbreak observatories in other geographic regions are presented.
A note on the depth of sidelobe contamination in acoustic doppler current profiles

(American Meteorological Society, 2022-01-01) Lentz, Steven J. ; Kirincich, Anthony R. ; Plueddemann, Albert J.

Acoustic Doppler current profilers (ADCP) do not provide reliable water velocity measurements near the sea surface or bottom because acoustic sidelobe reflections from the boundary contaminate the Doppler velocity measurements. The apparent depth of the center of the sidelobe reflection is zsl = ha[1 − cos(θ)], where ha is the distance from the ADCP acoustic head to the sea surface and θ is the ADCP beam angle. However, sidelobe contamination extends one and a half ADCP bins below zsl as the range gating of the acoustic return causes overlap between adjacent ADCP bins. Consequently, the contaminated region z < zsl + 3Δz/2 is deeper than traditionally suggested, with a dependence on bin size Δz. Direct observations confirming both the center depth of the sidelobe reflection and the depth of contamination are presented for six bottom-mounted, upward-looking ADCPs. The sidelobe reflection is isolated by considering periods of weak wind stresses when the sea surface is smooth and there is nearly perfect reflection of the main beams away from the ADCP and hence little acoustic return from the main beams to the ADCP.

Plueddemann Albert J.

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