The vertical structure of upper ocean variability at the Porcupine Abyssal Plain during 2012–2013

Abstract

This study presents the characterization of variability in temperature, salinity and oxygen concentration, including the vertical structure of the variability, in the upper 1000 m of the ocean over a full year in the northeast Atlantic. Continuously profiling ocean gliders with vertical resolution between 0.5 and 1 m provide more information on temporal variability throughout the water column than time series from moorings with sensors at a limited number of fixed depths. The heat, salt and dissolved oxygen content are quantified at each depth. While the near surface heat content is consistent with the net surface heat flux, heat content of the deeper layers is driven by gyre‐scale water mass changes. Below ∼150m, heat and salt content display intraseasonal variability which has not been resolved by previous studies. A mode‐1 baroclinic internal tide is detected as a peak in the power spectra of water mass properties. The depth of minimum variability is at ∼415m for both temperature and salinity, but this is a depth of high variability for oxygen concentration. The deep variability is dominated by the intermittent appearance of Mediterranean Water, which shows evidence of filamentation. Susceptibility to salt fingering occurs throughout much of the water column for much of the year. Between about 700–900 m, the water column is susceptible to diffusive layering, particularly when Mediterranean Water is present. This unique ability to resolve both high vertical and temporal variability highlights the importance of intraseasonal variability in upper ocean heat and salt content, variations that may be aliased by traditional observing techniques.

Wind‐Forced Symmetric Instability at a Transient Mid‐Ocean Front

“…(). Seaglider observations . In addition to the mooring observations, the OSMOSIS region (approximately 20 × 20 km) was continuously sampled by at least two (five in total) autonomous underwater gliders for the entire year (Damerell et al., ; Erickson & Thompson, ; Evans et al., ; Thompson et al., ). The gliders navigated in a bow tie pattern across the mooring array, measuring temperature and salinity profiles within the top 1,000 m of the ocean at approximately 1‐m depth intervals.…”

High‐Frequency Variability of Small‐Particle Carbon Export Flux in the Northeast Atlantic

“…The resulting volume scattering function β ( θ , λ ) includes both the particulate scattering signal and the scattering by pure seawater: β = β p + β sw (e.g., Stramski et al, ; Zhang et al, ). The scattering by seawater β sw was calculated using the model developed by Zhang et al (), using the calibrated temperature and salinity glider data (for calibration procedures, see Damerell et al, ), a depolarization ratio of 0.039, the wavelength λ of the respective sensor and an in‐water centroid angle θ of the ECOpuck scattering sensor of 124°. After subtraction of β sw , the particulate volume scattering function β p was converted to the particulate optical backscattering coefficient b bp , as (e.g., Briggs et al, ; Cetinić et al, ; Dall'Olmo & Mork, ), using a conversion coefficient χ p of 1.076 (for θ = 124°; Sullivan et al, ).…”

Testing Munk's hypothesis for submesoscale eddy generation using observations in the North Atlantic

“…OSMOSIS was a research consortium formed to better understand competing turbulent processes within the ocean surface boundary layer (SBL), including Langmuir turbulence and submesoscale processes. The observational component of the study included two process study cruises, year‐long mooring and year‐long glider observations, September 2012 to September 2013, all of which took place in the eastern North Atlantic (48.69°N, 16.19°W, Figure ) [ Allen et al ., ; Buckingham et al ., ; Thompson et al ., ; Damerell et al ., ]. In order to help with interpretation of these observations, we sought high‐resolution satellite imagery throughout the entire year.…”