Previous Research Projects
The Next Generation RAFOS Float: A More Capable, Cost-effective Subsurface Drifter for Observing Deep Ocean Currents
Co-PIs: Amy Bower (WHOI), H. Thomas Rossby (URI)
For over 40 years, acoustically tracked floats have provided a unique and valuable Lagrangian perspective on ocean circulation. Their high-resolution trajectories reveal plainly the variable pathways of narrow boundary currents, the orbiting motion of eddies, and spreading of water masses. Arguably, without acoustically tracked floats, we would be much less aware of the richness of coherent structures in the subsurface ocean and their impact on the transport of heat, salt, nutrients and other water properties. We are developing the next generation RAFOS float that will be smaller, lower-cost, more efficient, more capable and easier to use. The heart of the new design will be the recently completed and tested 'Fish Chip', a RAFOS receiver on a micro-chip that has been developed to track fish using RAFOS navigation.
A Lagrangian Study of the Deep Circulation in the Gulf of Mexico
Co-PIs: Amy Bower (WHOI), Peter Hamilton (Leidos), Paula Perez-Brunius (CICESE), and Bob Leben (U. Colorado)
This study was designed to map circulation throughout the deep Gulf of Mexico with a large number of subsurface neutrally buoyant floats, producing new knowledge on circulation features and processes, and deep-water parcel transport and dispersion. The instruments used were acoustically tracked RAFOS floats (ballasted for 1500- and 2500-dbar) to map water parcel pathways and profiling APEX floats equipped with bio-optical sensors, which profiled from the surface to 1500-dbar. Many RAFOS floats were deployed in pairs and triplets.
A Crossroads of the Atlantic Meridional Overturning Circulation: The Charlie-Gibbs Fracture Zone
Co-PIs: Amy Bower and Michael Spall WHOI)
The objectives of this experiment were (1) to obtain an improved direct estimate of the mean and low-frequency variability of the deep westward transport of the Iceland-Scotland Overflow Water through the Charlie-Gibbs Fracture Zone (CGFZ), and (2) to gain a better understanding of the causes of the low-frequency variability in the transport of overflow waters through the CGFZ, especially of the role of the North Atlantic Current in generating this variability. The mooring deployment and recovery cruises were on German research vessels, courtesy of Drs. Monika Rhein and Dagmar Kieke: the R/V Meteor cruise M82/2 in August 2010 and R/V Maria S. Merian cruise MSM 21/2 in June 2012, respectively. The CGFZ moored array complemented other moored arrays being maintained by German scientists just west of the CGFZ (Pressure Inverted Echo Sounders, or PIES) and the Faraday Fracture Zone (current meter and microcat moorings).
Irminger Rings in the Labrador Sea
PI: Amy Bower
The objectives of IRINGS were to (1) to determine the full water column hydrographic and velocity structure of newly formed Irminger Rings that have entered the interior Labrador Sea; (2) to observe how Irminger Ring core properties are modified by atmospheric forcing over their lifetime; and (3) to improve the interpretation of sea surface height (SSH) anomalies in terms of newly formed coherent heat containing Irminger Rings. The mooring deployment and recovery cruises were both on the R/V Knorr: KN192-01 in September 2007 and KN196-01 in September 2009, respectively. The single mooring held eight Aanderaa current meters (RCM-11), two Submerged Autonomous Launch Platforms (SALPs), and nine Seabird microcats (SBE37), deployed from 26 September 2007 through 27 September 2009, yielding full water column (100-3000 meters) records of temperature, salinity, pressure, and velocity data for the two year period. The two SALP cages contained eleven APEX floats, and released some of these floats according to local oceanographic conditions, so as to seed the floats in passing Irminger Rings, and the remainder of floats as timed releases. Thirteen conductivity-temperature-depth (CTD) stations were taken on the mooring recovery cruise, creating a boundary current cross-section from the mooring site to Nuuk, Greenland.
Red Sea Hydrography and Circulation (KAUST)
Co-PIs: Amy Bower, Robert Weller, J. Thomas Farrar
The Red Sea is an ocean basin of local, regional and global significance. It is a long and narrow sea, ringed by many Middle Eastern and African countries; coastal development in one country will have a profound impact on the entire region. It is fringed by extensive coral reefs, many in pristine condition, that provide critical habitat for marine life, support several important fisheries and attract tourists. Formed as the African and Arabian plates split apart, the Red Sea remains to this day an active rifting zone, generating earthquakes, volcanic eruptions, as well as deep hypersaline brine pools and valuable mineral deposits at the ocean floor. One of the world's busiest shipping routes and the largest seaport in the Middle East are in the Red Sea. In spite of its economic and environmental importance, our knowledge of the oceanographic conditions in the Red Sea, and the important physical, biological, geological and chemical processes remains somewhat limited.
Arabian Marginal Seas and Gulfs
Co-PIs: Amy Bower and Jim Price (WHOI)
We have analyzed hydrographic data collected by the U. S. Naval Oceanographic Office (NAVOCEANO) in the outflow region of two important marginal seas; the Red Sea and the Persian Gulf. Our goal was to describe the synoptic scale structure of the outflow hydrography, with particular emphasis on (1) mixing of the outflow currents with the oceanic environment; (2) the occurrence of eddy formation (i.e. Reddies) and (3) the effect of the outflows on the adjacent seas. The primary data resource for this analysis was the synoptic AXBT surveys acquired by NAVOCEANO in the Gulf of Aden and Gulf of Oman. We also used the one-dimensional outflow plume model of Price and Baringer (1994) to investigate the dynamics of these two outflows.
Red Sea Outflow Experiment (REDSOX)
Co-PIs: Amy Bower, Dave Frantantoni (WHOI), Bill Johns (RSMAS) and Hartmut Peters (RSMAS)
The Red Sea Outflow Experiment (REDSOX) was a joint effort between the University of Miami's Rosenstiel School of Marine and Atmospheric Science (RSMAS) and WHOI. The purpose of the program was to conduct measurements of the outflow of high salinity water from the Red Sea and its mixing with ambient waters in the Gulf of Aden. The main objectives of REDSOX were: 1) to describe the pathways and downstream evolution of the descending outflow plumes of Red Sea Water in the western Gulf of Aden, 2) to quantify the process that controls the final depth of the equilibrated Red Sea Outflow Water, and 3) to identify the transport processes and mechanisms that advect Red Sea Outflow Water and its properties through the Gulf of Aden and into the Indian Ocean.
Export Pathways from the Subpolar North Atlantic
Co-PIs: Amy Bower (WHOI) and Susan Lozier (Duke)
The Export Pathways Experiment was a joint effort between WHOI and Duke University. The purpose of the program was to study the pathways and variability of the Deep Western Boundary Current from the Labrador Sea into the subpolar North Atlantic. Our objectives were to: 1. Obtain an improved description of the pathways of LSW out of the subpolar region using acoustically-tracked RAFOS floats deployed in the DWBC in the Labrador Sea. 2. Characterize the intermittency/temporal variability in these pathways, and investigate its cause, including NAC position, interannual variations in LSW production, and seasonal/interannual variations in wind forcing. 3. Use historical and synoptic hydrographic data to determine low-frequency variations in the penetration of recently-ventilated water masses equatorward along the western boundary.
Atlantic Climate and Circulation Experiment: Warm Water Pathways and Intergyre Exchange
Co-PIs: Amy Bower and Phil Richardson (WHOI)
The North Atlantic Current, which transports subtropical water northeastward from the Gulf Stream, and the Poleward Eastern Boundary Current, which carries Mediterranean Outflow Water northward along the European continental slope have been proposed as the two most likely sources of the warm, salty water that is transformed into intermediate and deep water in the subpolar region. We studied the circulation in this region using isopycnal, acoustically-tracked RAFOS floats that were deployed in these two currents with the overall goal of describing the pathways of warm water towards the subpolar region. Our specific objectives were to 1) provide a quantitative description of the bifurcation of the North Atlantic Current east of the Mid-Atlantic Ridge; 2) assess the importance of meridional eddy fluxes, compared to large-scale advection, in the northward flux of heat and salt in the northeastern North Atlantic; and 3) establish the degree of continuity of the Poleward Eastern Boundary Current to the entrance to the Norwegian Sea and the fate of the Mediterranean Outflow Water carried by this current.
Deep Western Boundary Current
Co-PIs: Amy Bower, Robert Pickart (WHOI), William Smethie (LDEO)
In this study, hydrography, tracer measurements and float observations were combined to obtain the first comprehensive description of the North Atlantic Deep Western Boundary Current (DWBC) variability over a large path segment. The hydrographic portion consisted of two occupations (six months apart) of six finely resolved sections across the DWBC from the Grand Banks of Newfoundland to Cape Hatteras. Over this distance (roughly 1700 km) the DWBC encounters diverse conditions, including variations in bottom slope and roughness, as well as proximity to the Gulf Stream. The main objectives of the hydrographic study were to determine the synoptic velocity and water mass structure of the DWBC in order to investigate the nature and cause of the observed variability.
Mediterranean Outflow and Meddies
Co-PIs: Amy Bower, Lawrence Armi (SIO/UCSD), Isabel Ambar (U. Lisbon), and Phil Richardson (WHOI)
The Mediterranean salt tongue is a prominent feature of the North Atlantic Ocean at mid-depths. The discovery of isolated lenses of salty Mediterranean Water (meddies) in the last decade has challenged the traditional view of this tongue as a purely advective/diffusive feature. The role of these meddies in the salt and heat budgets of the North Atlantic is not well-understood. We studied the dispersion of Mediterranean Water into the North Atlantic via meddies and other processes.