pinecone/core-2020-05-10-deduplication huggingface dataset:
Air-sea and oceanic heat flux contributions to the heat budget\ud
of the northern Gulf of Alaska shelf

We constructed annual cycles of National Centers for Environmental Prediction air-sea\ud
fluxes and temporal oceanic heat content change from Seward Line hydrographic surveys\ud
to quantify the different contributions to the oceanic heat budget within the Alaska Coastal\ud
Current (ACC) on the northern Gulf of Alaska shelf. The deficit between air-sea fluxes and\ud
the temporal change in oceanic heat content throughout the cooling season (October–April)\ud
varies from ~40 to 110Wm�2 and is balanced by ocean heat flux convergence. Cross-shelf\ud
heat flux convergence is insignificant on annual average, and the nearshore heat budget is\ud
likely entirely balanced by the ACC, which resupplies ~15%–50% of the heat removed by\ud
air-sea fluxes during the cooling season. Furthermore, we estimated spatial heat flux\ud
gradients and conclude that air-sea fluxes increase from east to west and from offshore to\ud
onshore. The cross-shore gradients are governed by wind speed gradients, likely due to\ud
ageostrophic nearshore wind events during the cooling season, while the along-shelf heat\ud
flux gradients are governed by the occurrence of low-pressure systems in the northern\ud
GOA that result in cold northerly winds over the northwestern GOA. These results\ud
underline the ACC’s role as the dominant oceanic heat source to the northern GOA shelf\ud
and further imply an increased cooling rate of the ACC west of the Seward Line.\ud
Furthermore, our analysis showed that nearshore regions, particularly waters in the ACC,\ud
are subjected to stronger winter cooling than the middle and outer shelves
Inter-annual to decadal sea-level variability in the coastal zones of the Norwegian and Siberian Seas: The role of atmospheric forcing

Inter-annual to decadal sea-level variations from tide gauge records in the coastal zones of the Norwegian and Siberian Seas are examined for the period 1950–2010 using a combination of hydrographic observations, wind data, and theory. We identify two large areas of highly coherent sea-level variability: one that includes the Norwegian, Barents, and Kara Seas, and another one that includes the Laptev, East Siberian, and Chukchi Seas. We provide evidence of a new contribution to the sea-level variability along the Norwegian coast associated with the poleward propagation of sea-level fluctuations along the eastern boundary of the North Atlantic. When this propagating signal is combined with the local wind, we are able to explain over 70% of the variance along the Norwegian coast. The steric component explains ~61% of the sea-level (corrected for the inverse barometer) variability along the Norwegian coast. The high coherency between the sea level along the Norwegian coast and that in the Barents and Kara Seas suggests that part of the Norwegian signal propagates further north into these regions. We introduce an atmospheric vorticity index that explains much of the sea-level variability in the Laptev, East Siberian, and Chukchi Seas with correlations ranging from 0.73 to 0.81. In the East Siberian Sea, we identify a sea-level increase of ~22 cm between 2000 and 2003, which is partly explained by the vorticity index, and a decline of ~15 cm after 2003, which we relate to the strengthening of the Beaufort Gyre
A new observationally motivated Richardson number based mixing parametrization for oceanic mesoscale flow

Ocean models require subgrid-scale parametrizations of vertical mixing expressed in terms of a quantity that is easily diagnosable from model output, such as the Richardson number. To date parametrizing mixing for low (<1) Richardson number flows, such as the Equatorial Undercurrent, has received the most attention. Here a new Richardson number parametrization is proposed that provides estimates of vertical turbulent diffusivity in the high Richardson number stratified shear flow that is associated with mesoscale ocean features such as eddies and fronts. This parametrization is based on direct observations of vertical turbulent diffusivity from three separate ocean regions in the North Atlantic and Southern Ocean and is found to be robust for values of the Richardson number greater than 1 at depths below the ocean surface boundary layer. The new parametrization gives substantially improved agreement with the observed mixing in the presence of mesoscale ocean features compared to existing Richardson number parametrizations
MIMOC: A global monthly isopycnal upper-ocean climatology with mixed layers

A monthly, isopycnal/mixed-layer ocean climatology (MIMOC), global from 0 to 1950 dbar, is compared with other monthly ocean climatologies. All available quality-controlled profiles of temperature (T) and salinity (S) versus pressure (P) collected by conductivity-temperature-depth (CTD) instruments from the Argo Program, Ice-Tethered Profilers, and archived in the World Ocean Database are used. MIMOC provides maps of mixed layer properties (conservative temperature, Θ, absolute salinity, SA, and maximum P) as well as maps of interior ocean properties (Θ, SA, and P) to 1950 dbar on isopycnal surfaces. A third product merges the two onto a pressure grid spanning the upper 1950 dbar, adding more familiar potential temperature (θ) and practical salinity (S) maps. All maps are at monthly 0.5° × 0.5° resolution, spanning from 80°S to 90°N. Objective mapping routines used and described here incorporate an isobath-following component using a “Fast Marching” algorithm, as well as front-sharpening components in both the mixed layer and on interior isopycnals. Recent data are emphasized in the mapping. The goal is to compute a climatology that looks as much as possible like synoptic surveys sampled circa 2007–2011 during all phases of the seasonal cycle, minimizing transient eddy and wave signatures. MIMOC preserves a surface mixed layer, minimizes both diapycnal and isopycnal smoothing of θ-S, as well as preserves density structure in the vertical (pycnoclines and pycnostads) and the horizontal (fronts and their associated currents). It is statically stable and resolves water mass features, fronts, and currents with a high level of detail and fidelity
Role of advection in Arctic Ocean lower trophic dynamics: a modelling perspective

The Arctic Ocean (AO) is an oligotrophic system with a pronounced subsurface Chl-a maximum dominating productivity over the majority of the basin. Strong haline stratification of the AO and substantial ice cover suppress vertical mixing and restrict the vertical supply of nutrients to the photic zone. In such a vertically stratified oligotrophic system, the horizontal supply of nutrients by advection plays an important role in sustaining primary production. In this paper we attempt to characterise the role of nutrient advection in the maintenance of the subsurface Chl-a maximum, using time scales to determine the connectivity between the photic zone of the deep Arctic Ocean, nutrient-rich Pacific and Atlantic inflow waters, and bottom waters of the wide continental shelves of the AO.\ud
\ud
Our study uses output from a general circulation model, NEMO, coupled to a model of ocean biogeochemistry, MEDUSA. A Lagrangian particle tracking approach is used to back-track water from where it forms subsurface Chl-a maxima to the points of entry into the AO and to analyse nutrient transformation along the route.\ud
\ud
Our experiments show that advective timescales linking subsurface layers of the central AO with the nutrient rich Pacific and Atlantic waters do not exceed 15-20 years, and that the advective supply of shelf nutrients to the deep AO occurs on the timescale of about 5 years. We show substantial role of the continental shelf pump in sustaining up to 20% of total AO primary production
Seasonal variability and coastal upwelling near Cape Santa Marta (Brazil)

The Santa Marta Grande Cape (CSM) area, a relatively steep and narrow continental shelf off southeast Brazil, is under the influence of the Brazil Current and intense seasonal variations of the wind field that affect the composition of water masses and their circulation. Hydrographic data, satellite-derived wind stress, and numerical simulations are used to characterize the seasonal and shorter period variability of the oceanographic conditions off CSM, in the area between 27S and 30S. The study is focused on the upwelling episodes and the dynamical mechanisms associated with these events. Field data  and numerical results indicate significant seasonal changes in the oceanographic structure, the water mass composition, and the dynamical balance. During fall and winter, when southwesterly winds prevail and the frequency of meteorological frontal systems increases, the region is characterized by waters of continental origin, the Plata Plume Water (PPW). During spring and summer, deeper waters reach the surface layer due to the action of northeasterly winds. Coastal upwelling events are revealed by surface temperature minima observed south of CSM. Synoptic data show that these events occur in pulses associated with changes in the wind direction. Analysis of the numerical results shows that this  particular location of the upwelling band results from the synergy between shelf-break upwelling and the regional shelf circulation induced by the northeasterly winds, both of which are modulated by changes in the coastline orientation and shelf width.Fil: Campos, Paula C.. Universidade Federal do Rio Grande do Sul; BrasilFil: Moller Jr., Osmar O.. Universidade Federal do Rio Grande do Sul; BrasilFil: Piola, Alberto Ricardo. Universidad de Buenos Aires; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografia Naval; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Palma, Elbio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); Argentina. Universidad Nacional del Sur; Argentin
Assessment of Southern Ocean water mass circulation and characteristics in CMIP5 models: Historical bias and forcing response

The ability of the models contributing to the fifth Coupled Models Intercomparison Project (CMIP5) to represent the Southern Ocean hydrological properties and its overturning is investigated in a water mass framework. Models have a consistent warm and light bias spread over the entire water column. The greatest bias occurs in the ventilated layers, which are volumetrically dominated by mode and intermediate layers. The ventilated layers have been observed to have a strong fingerprint of climate change and to impact climate by sequestrating a significant amount of heat and carbon dioxide. The mode water layer is poorly represented in the models and both mode and intermediate water have a significant fresh bias. Under increased radiative forcing, models simulate a warming and lightening of the entire water column, which is again greatest in the ventilated layers, highlighting the importance of these layers for propagating the climate signal into the deep ocean. While the intensity of the water mass overturning is relatively consistent between models, when compared to observation-based reconstructions, they exhibit a slightly larger rate of overturning at shallow to intermediate depths, and a slower rate of overturning deeper in the water column. Under increased radiative forcing, atmospheric fluxes increase the rate of simulated upper cell overturning, but this increase is counterbalanced by diapycnal fluxes, including mixed-layer horizontal mixing, and mostly vanishes
Wave-current interactions in a wave-dominated tidal inlet

Wave-current interactions play a major role in the dynamics of shallow tidal inlets. This study investigates these interactions at a natural inlet, with a strong focus on current-induced changes on wave propagation. The analysis of hydrodynamic data collected at the Albufeira lagoon, Portugal, revealed spatiotemporal variations of water levels and wave heights along the inlet, attributed to wave-current interaction processes. We compared the simulations of a coupled wave-circulation modeling system, computed with and without waves, and propagated with and without current feedback. The wave-induced setup inside the lagoon represented 7%–15% of the offshore significant wave height. The accuracy of the wave's predictions improved when current feedback was included. During ebb, the currents increased the wave height at the mouth of the inlet (up to 20%) and decreased the wave height in the inlet (up to 40%), due to current-induced refraction, steepness dissipation, and partial blocking. During flood, the currents decreased the wave height in the inlet (up to 10%) and increased the wave height at the exterior parts of the ebb shoal (up to 10%), due to current-induced refraction. These effects significantly attenuate seaward sediment fluxes during ebb and contribute to the sediment accretion in the inlet
Assessment of Southern Ocean mixed-layer depth in CMIP5 models: historical bias and forcing response

The development of the deep Southern Ocean winter mixed layer in the climate models participating in the fifth Coupled Models Intercomparison Project (CMIP5) is assessed. The deep winter convection regions are key to the ventilation of the ocean interior, and changes in their properties have been related to climate change in numerous studies. Their simulation in climate models is consistently too shallow, too light and shifted equatorward compared to observations. The shallow bias is mostly associated with an excess annual-mean freshwater input at the sea surface that over-stratifies the surface layer and prevents deep convection from developing in winter. In contrast, modeled future changes are mostly associated with a reduced heat loss in winter that leads to even shallower winter mixed layers. The mixed layers shallow most strongly in the Pacific basin under future scenarios, and this is associated with a reduction of the ventilated water volume in the interior. We find a strong state dependency for the future change of mixed-layer depth, with larger future shallowing being simulated by models with larger historical mixed-layer depths. Given that most models are biased shallow, we expect that most CMIP5 climate models might underestimate the future winter mixed-layer shallowing, with important implications for the sequestration of heat, and gases such as carbon dioxide, and therefore for climate
(Sub-)inertial wave boundary turbulence in the Gulf of Valencia

7 páginas, 6 figuras.The bottom boundary layer above sloping topography can be highly turbulent, even in deep seas. This is demonstrated here using high-resolution 1-Hz sampling temperature sensors that were moored for 5 months every 0.5 m between 6.5 and 61 m above a 572 m deep seafloor promontory on the continental slope off Valencia, Spain. Using these data, turbulence parameters have been estimated. With time and in the vertical, values vary over four orders of magnitude. They have a dominant local inertial period which is modulated by an about 11 day periodicity associated with variations in a baroclinic unstable boundary current. When this current is strong and Eastward, the upslope phase of inertial wave generates convective turbulence which reaches closest to the bottom and therefore can effect sediment dispersal. In late winter, equally strong shear-induced turbulence in 50 m high Kelvin-Helmholtz (K-H) overturns is forced by 0.2 m s−1 off/downslope motions, which are preceded by periods of warming of a few 0.01°C before the cooler near-bottom water is suddenly flushed over the promontory into the basin. Such anomalously large K-H overturns occurred 6 times in the investigated winter period.This research was supported by the project\ud
COSTEM (CTM2009-07806). We thank the captain and the crew of the R/V Garcia del Cid for their kind assistance. We thank Martin Laan for all his enthusiastic development of NIOZ-thermistors. We are grateful to the UTM technicians for providing assistance during the data acquisition. M. R. is supported by a FPI grant (Ref. BES-2010-029949) from the Spanish Ministry of Economy and Competitiveness.Peer reviewe
Multiple jets in the Malvinas Current

[1] The velocity structure of the Malvinas Current is described based on the analysis of high-resolution hydrographic data and direct current observations. The data show that though the current width exceeds 150 km, the flow is concentrated in two relatively narrow (~10–20 km) jets. Within these cores, the direct observations indicate surface velocities exceeding 0.5 m.s−1. Surface drifter, satellite-derived mean dynamic topography, and sea surface temperature data suggest that the high-velocity jets are also ubiquitous features of the time mean circulation. Both jets appear to be continuous features extending more than 900 km along the western slope of the Argentine Basin. These jets closely follow the 200 and 1400 m isobaths. Additional high-velocity cores are apparent in direct current measurements and hydrographic observations, but these features are weaker and not continuous along the slope. Though the Malvinas Current transport is mostly barotropic, baroclinic jets are also identified in relative geostrophic velocity sections. The baroclinic jets are colocated with the barotropic jets. Our results suggest that the main Malvinas Current core is located over a relatively flat portion of the bottom, referred to as the Perito Moreno terrace. This observation is in agreement with recent seismic and geological evidence suggesting that in geological time scales the Malvinas Current played a key role in the configuration of the bottom sediments over the western slope of the Argentine Basin.Fil: Piola, Alberto Ricardo. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografia Naval; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Franco, Barbara Cristie. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); Argentina. Universidad Nacional del Sur. Departamento de Física; ArgentinaFil: Palma, Elbio Daniel. Universidad Nacional del Sur. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Argentino de Oceanografía (i); ArgentinaFil: Saraceno, Martin. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y Los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera; Argentin
Seasonal variability of water masses and transport on the Antarctic continental shelf and slope in the southeastern Weddell Sea

An array of five moorings was deployed from February 2009 to February 2010 across the Antarctic shelf and slope in the southeastern Weddell Sea (~18°W). Observations demonstrate the key processes responsible for variability in water masses and transport in the region. Rapid fluctuations in temperature and salinity throughout the year are linked with variability in wind stress over the array. This causes the deepening or shoaling of the pycnocline, past the depth of the moorings. In the upper 500 m, the seasonal cycle in salinity shows freshening in autumn, with the strongest freshening at the shallowest mooring (~250 m), furthest on-shelf. The sea ice concentration over the array exceeds 90% during this period and contributes a positive salt flux into the ocean during autumn. Freshening begins during strong along-shore (easterly) winds in late April 2009. This demonstrates that variations in Ekman transport and wind-driven mixing play a key role in determining the salinity of shelf waters around Antarctica. Transport of the Antarctic Slope Current also shows a seasonal cycle with a maximum during late April. Model simulations show the importance of along-shore advection, as the arrival of a fresh anomaly from upstream determines the timing of the salinity minimum at the array. These processes are likely to be important for other regions around the Antarctic continen
Observed near-surface flows under all tropical cyclone intensity levels using drifters in the northwestern Pacific

Journal of Geophysical Research, 118, 1-11,Data from drifters of the surface velocity program and tropical cyclones (TCs) of the Joint Typhoon Warning Center during 1985–2009 were analyzed to demonstrate strong currents under various storm intensities such as category-4 to 5, category-2 to 3, and tropical storm to category-1 TCs in the northwestern Paciﬁc. Current speeds over 2.0 m s1 are observed under major TCs with the strongest mean currents to the right of the storm track. This study provides the characterization of the near-surface velocity response to all recorded TCs, and agrees roughly with Geisler’s theory (1970). Our observations also verify earlier modeling results of Price (1983)
Toward representing wave-induced sediment suspension over sand ripples in RANS models

Parameterizations of near-bed sediment processes are commonly associated with the poor predictive skill of coastal sediment transport models. We implement a two-dimensional Reynolds-averaged Navier-Stokes model to directly assess these parameterizations by reproducing measurements obtained in large-scale wave flume experiments. A sediment transport model has been coupled to wave hydrodynamics and turbulence, and numerical experiments provide temporal and spatial variations of free surface, flow velocity, sediment concentration, and turbulence quantities. Model-data comparisons enable the direct assessment of how key suspension processes are represented and of the inherent variability of the sediment transport model. We focus on the different processes occurring above rippled beds versus dynamically flat beds. Numerical results show that increasing roughness alone is not sufficient to have good predictive capability above steep ripples. Some parameterization of the vortex entrainment process is necessary and a simple modification, which leads to constant sediment diffusivity above steep-rippled beds, is sufficient to obtain good predictions of wave-averaged suspended concentrations. Model-data comparisons for the turbulent kinetic energy are also presented and highlight the need to account for the effect of vortex entrainment on near-bed turbulence and transfer of momentum