A climatology of the California Current System from a network of underwater gliders

Rudnick, Daniel L.; Zaba, Katherine D.; Todd, Robert E.; Davis, Russ E

doi:10.1016/j.pocean.2017.03.002

Cited by 83 publications

(144 citation statements)

References 39 publications

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“…Temporal series of temperature, salinity and geostrophic velocity are analyzed to estimate for each variable a mean field, a linear tendency, and an annual cycle. At each grid point a harmonic function with a linear term is fitted to each variable,

A_{0} + A_{t} t + A_{c} \cos false(2 normalπ t false/ T false) + A_{s} \sin false(2 π t false/ T false),

where A 0 is the mean field, A t is the tendency, the period of the annual cycle is T = 365.25 days, the amplitude is defined as

{false[A_{c}^{2} + A_{s}^{2} false]}^{1 false/ 2}

, and the phase as

ϕ = \arctan false(- A_{s} false/ A_{c} false)

(Rudnick et al, ). Averaged vertical profiles of the skill of the regression, defined as 1 − var(residuals)/var(original), obtained from fitting this function to the temporal series of each variable are plotted in Figure (solid lines).…”

Section: Resultsmentioning

confidence: 99%

Temporal and Spatial Hydrodynamic Variability in the Mallorca Channel (Western Mediterranean Sea) From 8 Years of Underwater Glider Data

et al. 2019

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Eight years of glider data are used to characterize the temporal and spatial variability of a region in the western Mediterranean that will constitute one of the targets for the calibration phase of the Surface Water and Ocean Topography (SWOT) satellite mission. The characteristic horizontal dimension of mesoscale instabilities in the Mallorca channel is 6.0 km. The temporal evolution of intermediate water masses is dominated by an increase over time of the characteristic temperature values. Western Mediterranean and Levantine Intermediate waters display an increase of the temperature extrema of 0.064 ± 0.002 and 0.044 ± 0.002 °C/year between 2011 and 2018, respectively. At the layer of Levantine Intermediate water the salinity temporal regression reveals a mean trend of 0.010 year−1. Temperature annual cycle shows an averaged temperature gradient of ∼6 °C in 6 months at the upper layer, with a disconnection with the annual cycle at 100‐m depth. The circulation across the channel is dominated by high‐frequency variability. The signature of eddies with radius ranging from 5 to 18 km is apparent in 16% of the transects analyzed and mainly in spring and summer, with a dominance of subsurface cyclonic eddies. Two‐way flow controls the annual cycle of the water transport through the channel with prevalence of the inflow of Atlantic water. Variations of water transport over timescales of weeks to months can be similar to those identifiable as seasonal changes.

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A_{0} + A_{t} t + A_{c} \cos false(2 normalπ t false/ T false) + A_{s} \sin false(2 π t false/ T false),

where A 0 is the mean field, A t is the tendency, the period of the annual cycle is T = 365.25 days, the amplitude is defined as

{false[A_{c}^{2} + A_{s}^{2} false]}^{1 false/ 2}

, and the phase as

ϕ = \arctan false(- A_{s} false/ A_{c} false)

Section: Resultsmentioning

confidence: 99%

Temporal and Spatial Hydrodynamic Variability in the Mallorca Channel (Western Mediterranean Sea) From 8 Years of Underwater Glider Data

et al. 2019

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“…To attest to the validity of the propagation pattern discovered in the model

z_{26.5}

, evidence can be obtained from repeated multiyear cross‐shore temperature and salinity sections sampled by autonomous underwater gliders [ Rudnick , ]. Specifically, we extract the seasonal cycle in

z_{26.5}

using glider records at 34°N collected in 2007–2013 [ Rudnick et al ., ] and records at 47°N–48°N collected in 2003–2008 [ Pelland et al ., ]. The WA glider data were processed similarly to the model.…”

Section: Seasonal and Interannual Variability In The Oceanic Propertimentioning

confidence: 98%

“…The calculation for the CA data is as described in Rudnick et al . []. At each location, the sum of the annual and semiannual harmonics was fit to the observed isopycnal layer depths.…”

Section: Seasonal and Interannual Variability In The Oceanic Propertimentioning

confidence: 99%

“…The plot of

T_{26.5}

anomaly (Figure b) shows long‐term cooling in the southern part of the domain, which is not observed in the glider data [ Rudnick et al ., ] and may be associated with model limitations representing horizontal eddy heat fluxes near the southern boundary. North of 35°N, the warm anomaly is seen in summer 2014 at a time of the anomalously strong deepening of the isopycnal surface, which is also the time of the cold phase in the

T_{26.5}

seasonal cycle (see Figure b).…”

Section: Seasonal and Interannual Variability In The Oceanic Propertimentioning

confidence: 99%

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Seasonal and interannual variability in along‐slope oceanic properties off the US West Coast: Inferences from a high‐resolution regional model

2017

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A 6 year, 2009–2014 simulation using a 2 km horizontal resolution ocean circulation model of the Northeast Pacific coast is analyzed with focus on seasonal and interannual variability in along‐slope subsurface oceanic properties. Specifically, the fields are sampled on the isopycnal surface σ=26.5 kg m−3 that is found between depths of 150 and 300 m below the ocean surface over the continental slope. The fields analyzed include the depth z26.5, temperature T26.5, along‐slope current v26.5, and the average potential vorticity PV between σ = 26.5 and 26.25 kg m−3. Each field is averaged in the cross‐shore direction over the continental slope and presented as a function of the alongshore coordinate and time. The seasonal cycle in z26.5 shows a coherent upwelling‐downwelling pattern from Mexico to Canada propagating to the north with a speed of 0.5 m s−1. The anomalously deep ( −20 m) z26.5 displacement in spring‐summer 2014 is forced by the southern boundary condition at 24°N as a manifestation of an emerging strong El Niño. The seasonal cycle in T26.5 is most pronounced between 36°N and 53°N indicating that subarctic waters are replaced by warmer Californian waters in summer with the speed close 0.15 m s−1, which is consistent with earlier estimates of the undercurrent speed and also present v26.5 analyses. The seasonal patterns and anomalies in z26.5 and T26.5 find confirmation in available long‐term glider and shipborne observations. The PV seasonality over the slope is qualitatively different to the south and north of the southern edge of Heceta Bank (43.9°N).

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“…Shown are modeled and observed (a, b) alongshore geostrophic velocity, (c, d) potential density, (e, f) NO 3 , and (g, h) Chl‐a along lines of the California Cooperative Oceanic Fisheries Investigation (CalCOFI) observational network in central California (33–38°N; see Figure b). Observational data for geostrophic velocity and potential density are taken from the California Underwater Glider Network (Rudnick et al, ) along Line 66.7 of the CalCOFI network. In situ measurements for NO 3 and Chl‐a are compiled from Line 60 to Line 80 climatologies of the CalCOFI network (http://calcofi.org/data.html).…”

Section: Model Evaluationmentioning

confidence: 99%

Origin, Transformation, and Fate: The Three‐Dimensional Biological Pump in the California Current System

2018

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While the Ekman drift as the cause for the high productivity of the California Current System was unraveled more than a century ago, it is less clear where the nutrients within the upwelling waters are coming from, and what the fate of the produced organic matter is. Here we address these questions using a high‐resolution simulation with a regional coupled physical/biogeochemical/ecological model within a Pacific Ocean setup. Our results, emerging from both Eulerian and Lagrangian analyses, reveal that prior to coastal production, inorganic nutrients get transported laterally over thousands of kilometers toward central California. More than 80% of the nutrients originate from central offshore or southern alongshore locations. About half of it is supplied by the California Undercurrent alone, underscoring its importance in sustaining the high coastal productivity. Even though most of the inorganic nutrients get quickly transformed into organic matter once upwelled to the euphotic layer along the coast, a substantial fraction remains unused. Together with these unused nutrients, about 36% of the organic matter produced within the nearshore 100 km gets laterally exported toward the open ocean, mostly in southwestward direction. This leakage of inorganic nutrients from the coastal zone and the continuous recycling of organic matter along the way support up to 24% of the overall observed production at a distance of 500 km from the coast. This set of processes linking the origin, biological transformation, and fate of nutrients support the growing view of the biological pump being an inherently three‐dimensional process.

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A climatology of the California Current System from a network of underwater gliders

Cited by 83 publications

References 39 publications

Temporal and Spatial Hydrodynamic Variability in the Mallorca Channel (Western Mediterranean Sea) From 8 Years of Underwater Glider Data

Temporal and Spatial Hydrodynamic Variability in the Mallorca Channel (Western Mediterranean Sea) From 8 Years of Underwater Glider Data

Seasonal and interannual variability in along‐slope oceanic properties off the US West Coast: Inferences from a high‐resolution regional model

Origin, Transformation, and Fate: The Three‐Dimensional Biological Pump in the California Current System

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