Category: Physical Oceanography

Interannual variations of the MOC (black) and contributions from the geostrophic (red) and Ekman (green) components at 20°S, 25°S, 30°S, and 34.5°S, respectively. The gray shading denotes the range where anomalies are not significantly different from zero. The red and green shading denote the periods of the dominance of the geostrophic and Ekman components on the MOC, respectively. Image Credit: NOAA.

Dominance of the Geostrophic and Ekman Transports on the MOC in the South Atlantic

The Meridional Overturning Circulation (MOC) plays a critical role in global and regional heat and freshwater budgets. Recent studies have suggested the possibility of a southern origin of the anomalous MOC and meridional heat transport (MHT) in the Atlantic, through changes in the transport of warm/salty waters from the Indian Ocean into the South Atlantic basin. This possibility clearly manifests the importance of understanding the South Atlantic MOC (SAMOC). Observations in the South Atlantic have been historically sparse both in space and time compared to the North Atlantic. To enhance our understanding of the MOC and MHT variability in the South Atlantic, a new methodology is recently published to estimate the MOC/MHT by combining sea surface height measurements from satellite altimetry and in situ measurements (Dong et al., 2015).

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NOAA's Ship of Opportunity Program coordinates a fleet of vessels that collect surface ocean CO2 measurements across the world's oceans. Image credit: NOAA

AOML-led Carbon Dioxide Sampling Effort Helps Quantify the Ocean’s Role in Global Carbon Budget

Researchers with the Global Carbon Budget released their annual update for the global carbon budget in December 2015, revealing carbon dioxide (CO2) emissions from fossil fuels increased slightly in 2014 (+0.6%), but are projected to decline slightly (by est. -0.6%) in 2015. The global oceans serve as a natural buffer, offsetting increased emissions by absorbing an estimated 27% of human-produced CO2 from the atmosphere in 2014. Data collected, in part, from long-term surface ocean CO2 monitoring efforts, funded by NOAA’s Climate Program Office and the Ocean Acidification Program, indicate that the oceans removed about 10.7 billion tons of CO2 from the atmosphere in 2015.

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An image of the successfully retrieved glider, including puncture marks from an encounter with a shark. Image credit: NOAA

Underwater Gliders Retrieved After Successful Third Mission

On November 16th-18th, AOML physical oceanographers partnered with the University of Puerto Rico to successfully recover two underwater gliders from the Caribbean Sea aboard the M/V La Sultana of the University of Puerto Rico Mayaguez. Over the course of the summer, the gliders successfully transected a region in the eastern Caribbean providing approximately 3000 profile observations of temperature, salinity, oxygen, and surface as well as depth-average current velocities.

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AOML scientists work with members of the ships' crew to recover the CTD rosette at the end of a 3 hour hydrographic cast. Image credit: NOAA

October 2015 Western Boundary Time Series Cruise

AOML oceanographers are participating in a joint research cruise to study the Meridional Overturning Circulation onboard the R/V Endeavor during October 3-20. The team will sail from Fort Lauderdale, FL to collect roughly 55 full-depth conductivity-temperature-depth (CTD) profiles in the Florida Current and the Deep Western Boundary Current east of the Bahamas. The scientists will also work with their partners from the University of Miami to recover, redeploy, and maintain three tall moorings and nine smaller moored instruments during this cruise in support of the NOAA Western Boundary Time Series project and its partner National Science Foundation project.

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Figure 3 Glider approximate location (black diamond) superimposed on Infrared image of Hurricane Gonzalo on October 14, 1500 UTC, when it travelled the closest to the location of the underwater glider. Credit: image obtained from the Cooperative Institute for Meteorological Satellite Studies.

Underwater gliders observations reveal the importance of salinity effects during passage of Hurricane Gonzalo (2014)

Hurricanes are known to drive the cooling of surface waters as they travel over the ocean, leaving a cooling swath where they pass. The sea surface cooling is mostly caused by mixing forced by the strong winds of the hurricane, which occurs as the mixture of warm surface waters with colder waters that can be as deep as 100 m below the surface.

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AOML oceanographer Andy Stefanick deploys the dropsonde at one of the stations during the 100th successful dropsonde cruise on October 15, 2015.

100th Successful Dropsonde Cruise for the Western Boundary Time Series Project

In October, AOML scientists, technicians and engineers involved in the Western Boundary Time Series (WBTS) project completed the 100th successful dropsonde cruise in the Florida Current since the project’s inception in 2000. The dropsonde cruises measure volume transport in the Florida Current using an out-of-service telephone cable between Florida and Grand Bahama Island.

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Trajectories of all drifters that were deployed during the January 2007 cruise. The drifters were drogued at 15 m depth, and each point represents a 6 hour subsampled location of a drifter. The trajectories clearly show the northern and southern circulation regimes, and illustrate the connectivity between the MBRS, Gulf of America, south Florida, and Cuba coastal waters. Image Credit: NOAA

Pathways and hydrography in the Mesoamerican Barrier Reef System

The results of two oceanographic cruises conducted in the Mexican and Belizean shelf waters over the Mesoamerican Barrier Reef during 2006 and 2007 show that the circulation can be divided into two distinct regimes: a northern region dominated by the strong, northward-flowing Yucatan Current, and a southern region with weaker southward coastal currents and the presence of the Honduras Gyre.

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Research Shows Indian Ocean Plays Key Role in Global Warming Hiatus

The earth is warming, but atmospheric and oceanic temperatures that rose steadily over the last half century have leveled off and slowed this past decade, causing the appearance of an imbalance in the Earth’s heat budget. Scientists looking to the deep ocean for where the additional heat energy might be stored recently traced a pathway that leads to the Indian Ocean.

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Above the clouds sunset from tropical storm Erika in 2015. Photo Credit, NOAA AOML.

Behind the 2015 Atlantic Hurricane Season: Wind Shear & Tropical Cyclones

With the 2015 Atlantic hurricane season underway, researchers are pointing to the strong presence of El Niño as the major driver suppressing the development of tropical cyclones in the Atlantic basin. But what specific conditions are associated with El Niño that lead to a less than ideal environment for tropical cyclone development? Through research and observation, hurricane researchers know strong environmental wind shear is a major factor affecting potential hurricane development and growth. This hurricane season, AOML researchers are delving further into the relationship between wind shear and tropical cyclones.

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