Quasi-Lagrangian observations of the upper ocean response to wintertime forcing in the Gulf Stream

Silverthorne, Katherine E.; Toole, John M.

doi:10.1016/j.dsr2.2013.02.021

Cited by 5 publications

(5 citation statements)

References 18 publications

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“…Drifting spar buoys generally require less motion correction, experience less flow-distortion and place sensors above the difficult-to-resolve processes within the wave-boundary layer (Hara and Sullivan, 2015); all of which results in accurate direct flux estimates (Edson et al, 2013;Drennan et al, 2014). Another advantage of a Lagrangian measurement of the air-sea fluxes in combination with oceanic temperature and salinity is that, to the extent the drifter follows the mean mixed layer currents, an ocean heat budget assessment can be simplified by reducing the advective flux divergence contribution to the budget (e.g., Silverthorne and Toole, 2013). Thus the surface fluxes measured by a drifter can be more directly constrained by changes in the upper ocean heat or salt content, and more directly compared to one-dimensional ocean models to evaluate the effects of surface forcing on the upper ocean (e.g., du Penhoat et al, 2002).…”

Section: CMmentioning

confidence: 99%

Air-Sea Fluxes With a Focus on Heat and Momentum

et al. 2019

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Turbulent and radiative exchanges of heat between the ocean and atmosphere (hereafter heat fluxes), ocean surface wind stress, and state variables used to estimate them, are Essential Ocean Variables (EOVs) and Essential Climate Variables (ECVs) influencing weather and climate. This paper describes an observational strategy for producing 3-hourly, 25-km (and an aspirational goal of hourly at 10-km) heat flux and wind stress fields over the global, ice-free ocean with breakthrough 1-day random uncertainty of 15 W m −2 and a bias of less than 5 W m −2. At present this accuracy target is met only for OceanSITES reference station moorings and research vessels (RVs) that follow best practices. To meet these targets globally, in the next decade, satellite-based observations must be optimized for boundary layer measurements of air temperature, humidity, sea surface temperature, and ocean wind stress. In order to tune and validate these satellite measurements, a complementary global in situ flux array, built around an expanded OceanSITES network of time series reference station moorings, is also needed. The array would include 500-1000 measurement platforms, including autonomous surface vehicles, moored and drifting buoys, RVs, the existing OceanSITES network of 22 flux sites, and new OceanSITES expanded in 19 key regions. This array would be globally distributed, with 1-3 measurement platforms in each nominal 10 • by 10 • box. These improved moisture and temperature profiles and surface data, if assimilated into Numerical Weather Prediction (NWP) models, would lead to better representation of cloud formation processes, improving state variables and surface radiative and turbulent fluxes from these models. The in situ flux array provides globally distributed measurements and metrics for satellite algorithm development,

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Section: CMmentioning

confidence: 99%

Air-Sea Fluxes With a Focus on Heat and Momentum

et al. 2019

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“…This surface heat loss initiates strong convection in the Sargasso Sea, which can lead to mixed layer depths (MLD) of up to 500 m (Buckley et al., 2014; Rossby, 1999). Re‐stratification then preserves beneath the surface the 18 Degree Water formed in the early spring (Leetmaa, 1977; Mensa et al., 2013; Silverthorne & Toole, 2013). This deepening of the thermocline combined with an increase in meridional temperature gradients across the GS will have a significant influence on its baroclinic transport, given the thermal wind relation (Bane & Osgood, 1989; Kelly et al., 1996; Leetmaa, 1977; Sato & Rossby, 1995; S. Dong et al., 2007), see Section 2.2.…”

Section: Introductionmentioning

confidence: 99%

“…Strong heat losses, and associated buoyancy forcing, are often induced during widespread outbreaks of cold, continental air from the northeast of North America extending over the GS region (Bane & Osgood, 1989; Grossman & Betts, 1990; Joyce et al., 2009; Kelly et al., 2010; Ma et al., 2015). These losses are often the largest seen globally with extreme values sometimes exceeding 1,000 Wm −2 during an outbreak (Silverthorne & Toole, 2013). This surface heat loss initiates strong convection in the Sargasso Sea, which can lead to mixed layer depths (MLD) of up to 500 m (Buckley et al., 2014; Rossby, 1999).…”

Section: Introductionmentioning

confidence: 99%

The Major Role of Air‐Sea Heat Fluxes in Driving Interannual Variations of Gulf Stream Transport

et al. 2020

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The Gulf Stream (GS) is the Western Boundary Current of the North Atlantic subtropical gyre and facilitates transport of warm, saline water from the subtropics to higher latitudes by rapid advection (Rossby, 1996). It begins as the Florida Current as it flows along the coast until it reaches Cape Hatteras, at about 75°W, where it then turns northeast and heads toward the Grand Banks as the GS proper, see Figure 1 (Schmitz, 1996). Peak transport of the separated GS reaches ∼150 Sv between 55°W and 60°W (Knauss, 1969; N. G. Hogg, 1992; Richardson, 1985; Rossby, 1996) and, on interannual timescales, can vary by more than 10% (Rossby et al., 2010). Significant uncertainty remains over the dominant controls on GS interannual variability (e.g., S. Dong et al., 2019). Here we explore the extent to which winter surface heat loss and wind stress curl variations have led to GS variability over the last three decades using a 1/12° global ocean model hindcast. Near 50°W by the Newfoundland ridge, the GS transport decreases as it branches into the North Atlantic Current (Rossby, 1999; Schmitz, 1996), which has multiple convoluted pathways due to higher eddy variability in this region (Bower & von Appen, 2008). The warm, salty water transported by the GS flows northward into the eastern subpolar gyre, where it cools and is preconditioned for the formation of deep waters seen in much of the global ocean (Bower & von Appen, 2008). In addition to the North Atlantic Current, the GS also splits into the Southern Recirculation Gyre (SRG), the Northern Recirculation Gyre

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“…The advection was particularly important in the convergence of warmer and saltier water in the formation region which changed the characteristics of the EDW in its early stages. Silverthorne and Toole () deployed quasi‐Lagrangian profilers in the GS region to observe changes in the heat storage in the upper ocean. During the winter the variations of heat storage in the mixed layer were dominated by forcing associated with the passage of severe storms.…”

Section: Introductionmentioning

confidence: 99%

Examining the Subtropical Mode Water in the Southwestern Atlantic From in Situ Observations

et al. 2019

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We investigated the formation and evolution of the South Atlantic subtropical mode water using data from profiling conductivity, temperature, and depth sensors (CTD) deployed in April–May 2015 and from two customized Argo floats that drifted from April 2015 to June 2017. From the CTD data, we observed a mode water layer below the seasonal thermocline that deepened from the southern side of the area to the north. The two Argo floats remained in the proximity of the cruise area for 2 years. Their slow displacement and recirculating patterns allowed us to observe the changes in the temperature and salinity structure before and after the formation period. We observed that the potential vorticity of newly formed mode water was O[10−1 to 10−2] of the mean value found in the whole mode water layer. There is a significant correspondence between the phases of the time integral of surface heat fluxes and the sea surface temperature. Mode water is observed to form at the integrated heat flux minimum phase. The relationship between the air‐sea fluxes and sea surface temperature promotes the necessary preconditioning for the mode water formation. Once this was established, the outcropping of the mode water, that was at about 100 m depth, coincided with the passage of an atmospheric cold frontal system. This event suggests that the mode water formation can be triggered by the passage of cold fronts.

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Quasi-Lagrangian observations of the upper ocean response to wintertime forcing in the Gulf Stream

Cited by 5 publications

References 18 publications

Air-Sea Fluxes With a Focus on Heat and Momentum

Air-Sea Fluxes With a Focus on Heat and Momentum

The Major Role of Air‐Sea Heat Fluxes in Driving Interannual Variations of Gulf Stream Transport

Examining the Subtropical Mode Water in the Southwestern Atlantic From in Situ Observations

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