• Issue

    Journal of Geophysical Research: Oceans: Volume 123, Issue 3

    1583-2314
    March 2018

Issue Information

Free Access

Issue Information

  • Pages: 1583-1585
  • First Published: 25 April 2018

Introduction to a Special Section

Free Access
Highlight

Atmosphere-Ice-Ocean-Ecosystem Processes in a Thinner Arctic Sea Ice Regime: The Norwegian Young Sea ICE (N-ICE2015) Expedition

  • Pages: 1586-1594
  • First Published: 28 February 2018
Key Points

  • An interdisciplinary expedition in the Atlantic sector of the high-Arctic studied the dynamics of a thin (<1.5 m) sea ice regime
  • Observations in a rarely sampled region, especially in winter, highlight the conditions in the Atlantic sector of the Arctic basin
  • Especially short-lived passing storms, with high winds and air temperatures and precipitation, leave a lasting impact on the sea-ice system

Research Articles

Free Access

Direct Numerical Simulation of Oscillatory Flow Over a Wavy, Rough, and Permeable Bottom

  • Pages: 1595-1611
  • First Published: 28 December 2017
Key Points

  • Hydrodynamic force acting on sediment particles is strongly affected by coherent vortex structures propagating close to the bed
  • Transition to turbulence is induced by the wavy bed at a value of the Reynolds number significantly smaller than in absence of waviness
  • The time development of the bed shear stress is shown and split into the viscous, turbulent, and “form” contributions

Free Access

Reconstruction of the 3-D Dynamics From Surface Variables in a High-Resolution Simulation of North Atlantic

  • Pages: 1612-1630
  • First Published: 05 February 2018
Key Points

  • In the Gulf Stream area, sea level is a better predictor of pressure and potential vorticity compared to surface temperature and salinity
  • Estimating pressure at depth from an inversion of potential vorticity or a direct linear regression from sea level have comparable skills
  • The depth of skillful reconstructions decreases from more than 1,000 m at scales larger than 200 km down to 200 m at 100 km wavelengths

Free Access

Fragmented Canopies Control the Regimes of Gravity Current Development

  • Pages: 1631-1646
  • First Published: 11 February 2018
Key Points

  • Hydrodynamics of gravity currents
  • Gravity currents in fragmented canopies in coastal regions
  • Sedimentation rates from gravity currents in fragmented canopies

Free Access

Vertical Mixing Effects on Phytoplankton Dynamics and Organic Carbon Export in the Western Mediterranean Sea

  • Pages: 1647-1669
  • First Published: 13 January 2018
Key Points

  • Phytoplankton dynamics and organic carbon export are compared in three Mediterranean regions, differentiated by the mixed layer depth
  • Despite a subpolar regime in the north and a subtropical regime in the south, annual primary production is similar in the studied regions
  • Organic carbon export below 150 (800) m was 4–5 (3–8) times higher in convective regions than in the stratified region, in 2012/2013

Free Access

Secondary Circulation Asymmetry in a Meandering, Partially Stratified Estuary

  • Pages: 1670-1683
  • First Published: 25 January 2018
Key Points

  • Channel meanders transform along-channel flows into asymmetric secondary circulation and into turbulence
  • At flood tidal phases, channel meanders enhance vertical mixing; at ebb phases, channel meanders enhance lateral currents
  • Channel meanders tend to reduce the flood-directed transport of momentum and the extent of salinity intrusion

Free Access
Highlight

Isotopic Evidence for the Evolution of Subsurface Nitrate in the Western Equatorial Pacific

  • Pages: 1684-1707
  • First Published: 11 February 2018
Key Points

  • Remineralization adds 15N-enriched nitrate to the southern hemisphere thermocline at the southern edge of the equatorial Pacific upwelling
  • Isotope tracers indicate the remineralization of 15N-depleted nitrate due to N2 fixation in the northern Pacific thermocline waters
  • Mixing estimates suggest a predominantly southern hemispheric source to the Equatorial Undercurrent that supplies the equatorial Pacific upwelling

Free Access

Steepest Ascent Low/Non-Low-Frequency Ratio in Empirical Mode Decomposition to Separate Deterministic and Stochastic Velocities From a Single Lagrangian Drifter

  • Pages: 1708-1721
  • First Published: 25 January 2018
Key Points

  • New method to determine 2-D turbulent characteristics from a single Lagrangian drifter
  • Effectiveness of using the empirical mode decomposition for the ocean community
  • Mesoscale eddy characteristics in the California Current system identified from RAFOR floats

Free Access

Oxygen Pathways and Budget for the Eastern South Pacific Oxygen Minimum Zone

  • Pages: 1722-1744
  • First Published: 02 March 2018
Key Points

  • Upper OMZ layer is mainly ventilated by mean circulation inside the Subtropical Cell (STC). Below the STC, turbulence dominates ventilation
  • One-way dianeutral entrainment accounts for 25.8% of the oxygen lost in this OMZ, most of it upwelling into the Ekman layer within the STC
  • The tropical-equatorial pathway provides 59.9% of the net oxygen supply while the subtropical pathway contributes with 28.6%

Free Access
Highlight

Multiscale Observations of Deep Convection in the Northwestern Mediterranean Sea During Winter 2012–2013 Using Multiple Platforms

  • Pages: 1745-1776
  • First Published: 14 December 2017
Key Points

  • We study deep convection and subsequent bloom in the northwestern Mediterranean Sea based on modern observation techniques
  • We provide estimates of mass and energy fluxes over a period of a year in the deep convection area and deep water formation rates
  • We highlight small-scale circulation features that are important for deep convection and subsequent bloom and introduce this special issue

Free Access

A Model-Based Evaluation of the Inverse Gaussian Transit-Time Distribution Method for Inferring Anthropogenic Carbon Storage in the Ocean

  • Pages: 1777-1800
  • First Published: 01 February 2018
Key Points

  • Uncertainty of the IG-TTD method is evaluated using model simulated anthropogenic carbon and transient tracers
  • Globally a lower and upper limit of uncertainty of 7.8% and 13.6% is found, smaller than previous estimates
  • Regional and parameter contributions to the uncertainty are quantified, and potential improvements of the method are suggested

Free Access

Bio-Optical Data Assimilation With Observational Error Covariance Derived From an Ensemble of Satellite Images

  • Pages: 1801-1813
  • First Published: 11 February 2018
Key Points

  • An ensemble approach to specify observational error covariance in the data assimilation of satellite bio-optical properties is proposed
  • The assimilation run with proposed covariance has higher errors than the run when observational errors equal 10% of the ensemble mean
  • The run with proposed covariance has smaller or comparable errors than the run when observational errors equal to 35% of the ensemble mean

Open Access

Low-Frequency Oceanographic Variability Near Flemish Cap and Sackville Spur

  • Pages: 1814-1826
  • First Published: 15 February 2018
Key Points

  • The first year-long moored measurements on Flemish Cap slope reveal highly variable flow
  • Velocity spectra have a prominent peak at 21 days, with power increasing toward the seabed
  • Dynamical analysis suggests bottom-trapped topographic Rossby waves may dominate low-frequency flow

Open Access

Land Ice Freshwater Budget of the Arctic and North Atlantic Oceans: 1. Data, Methods, and Results

  • Pages: 1827-1837
  • First Published: 20 February 2018
Key Points

  • Freshwater has been accumulating in Baffin Bay for 20 years
  • The freshwater anomaly has reached 6,300 km3
  • Important source of labile nutrients to coastal water

Free Access

Diagnostic Characteristics of Submesoscale Coastal Surface Currents

  • Pages: 1838-1859
  • First Published: 01 February 2018
Key Points

  • Energy spectra of coastal surface currents have decay slopes between k−2 and k−3 at a wave number (k) of 0.5 km−1
  • Injection scales estimated from submesoscale coastal surface current observations appear between 7 and 13 km
  • High-frequency radar-derived surface currents as a practical and unique resource for submesoscale process studies

Free Access

Variability in Benthic Exchange Rate, Depth, and Residence Time Beneath a Shallow Coastal Estuary

  • Pages: 1860-1876
  • First Published: 11 February 2018
Key Points

  • Measurements of differential pressure and wave parameters can be used to estimate wave-driven benthic exchange in the field
  • Wave-induced benthic exchange rates exceeded current and tide-induced rates by over an order of magnitude in a shallow estuary
  • Numerical model shows hydraulic diffusivity and wave parameters control wave-induced benthic exchange rate, depth, and residence time

Free Access

Investigating the Uncertainty in Global SST Trends Due to Internal Variations Using an Improved Trend Estimator

  • Pages: 1877-1895
  • First Published: 15 February 2018
Key Points

  • Internal variation determines the sign of secular trend in SST in most of global region
  • A new trend estimator is proposed to estimate the uncertainty in trend due to internal variation
  • It is hard to conclude how SST response to global warming in most of global regions using available SST records

Free Access

Water Mass Classification on a Highly Variable Arctic Shelf Region: Origin of Laptev Sea Water Masses and Implications for the Nutrient Budget

  • Pages: 1896-1906
  • First Published: 20 February 2018
Key Points

  • Principle component analysis allows classification of highly variable Laptev Sea water masses
  • Imported waters dominate the nutrient budget in the central Laptev Sea in years with weak polynya activity
  • Enhanced local polynya activity changes the nutrient budget significantly

Free Access

Estimation of Antarctic Land-Fast Sea Ice Algal Biomass and Snow Thickness From Under-Ice Radiance Spectra in Two Contrasting Areas

  • Pages: 1907-1923
  • First Published: 23 February 2018
Key Points

  • New algorithms to estimate Antarctic land-fast sea ice algal biomass and snow thickness from under-ice radiance spectra
  • The algorithms were developed for high biomass regimes in columnar and incorporated platelet ice
  • Inclusion of chlorophyll a-specific ice algal absorbance and pigment packaging slightly affect biomass predictability

Free Access

Oil Slick Observation at Low Incidence Angles in Ku-Band

  • Pages: 1924-1936
  • First Published: 22 February 2018
Key Points

  • Oil spill observation at low incidence angles
  • Retrieval of total mean square slope of sea waves within a wide swath

Free Access

Mesoscale and Submesoscale Processes in the Southeast Atlantic and Their Impact on the Regional Thermohaline Structure

  • Pages: 1937-1961
  • First Published: 22 February 2018
Key Points

  • Mesoscale spatiotemporal variability in the Cape Basin is also influenced by submesoscale mechanisms
  • Seasonality of the flow instabilities highly affects the dynamics of the upper and lower thermocline water masses
  • Small-scale processes strongly impacts the Indo-Atlantic transports of heat and salt

Free Access

A Study of Baroclinic Instability Induced Convergence Near the Bottom Using Water Age Simulations

  • Pages: 1962-1977
  • First Published: 01 February 2018
Key Points

  • Convergence in response to eddy transport causes upward extension of bottom material
  • Intensity of bottom tracer flux is determined by horizontal slope burger number
  • Spatial patchiness in bottom oxygen concentrations is caused by eddy activity

Free Access

Sea-Level Trend Uncertainty With Pacific Climatic Variability and Temporally-Correlated Noise

  • Pages: 1978-1993
  • First Published: 13 March 2018
Key Points

  • Accounting for ENSO and PDO variability does not affect the type of noise model that best describes the sea-level trend residual
  • Standard errors may be under (or over) estimated by assuming an AR(1) noise model when compared to a more realistic noise model
  • The observed trend in the satellite altimetry era emerges from the intrinsic noise for some key locations in the Indian and Pacific Oceans

Free Access

Transformation of Deep Water Masses Along Lagrangian Upwelling Pathways in the Southern Ocean

  • Pages: 1994-2017
  • First Published: 14 March 2018
Key Points

  • Upwelling of deep water is largely isopycnal in the Southern Ocean interior even at topographic upwelling hot spots
  • Atlantic and Indian Deep Waters cool and freshen significantly along interior isopycnals, homogenizing deep water
  • Significant transformation to lighter densities occurs below the mixed layer due to mixing with fresher surface waters

Free Access

Contrasting Impact of Future CO2 Emission Scenarios on the Extent of CaCO3 Mineral Undersaturation in the Humboldt Current System

  • Pages: 2018-2036
  • First Published: 28 February 2018
Key Points

  • Nearshore waters off Peru are bound to become undersaturated with respect to aragonite in the next decades
  • In a high CO2 emission scenario year-round calcite undersaturation will develop by the end of the century
  • If a low emission scenario was followed, the development of calcite undersaturation can likely be avoided

Open Access

Reconstructing Tropical Pacific Sea Level Variability for the Period 1961–2002 Using a Linear Multimode Model

  • Pages: 2037-2048
  • First Published: 02 March 2018
Key Points

  • A linear, multimode model driven by reanalysis wind stress products has skill at reproducing monthly mean sea level variability as measured by tide gauges in the presatellite era
  • A spurious eastward trend in the zonal wind stress in the NCEP/NCAR product leads to a spurious upward trend in model-computed sea level in the eastern Pacific
  • The pivot point at the equator was further west during 1993–2014 than earlier due to an upward trend in zonal wind stress variance in the western equatorial Pacific

Free Access

Dynamical Characterization of a Low Oxygen Submesoscale Coherent Vortex in the Eastern North Atlantic Ocean

  • Pages: 2049-2065
  • First Published: 01 February 2018
Key Points

  • Characterization of a submesoscale coherent vortex (100 km diameter) from multiplatform observations
  • Vortex with a well-isolated core of water with distinct thermohaline properties and very low oxygen concentration
  • Possible dynamical causes of small-scale thermohaline and oxygen filaments on the vortex rim are discussed

Free Access

Long Wave Runup in Asymmetric Bays and in Fjords With Two Separate Heads

  • Pages: 2066-2080
  • First Published: 02 March 2018
Key Points

  • Modeling long waves in bays with asymmetric cross sections using the CSA SWEs
  • Generalizing the TH transformation to bays with arbitrary cross sections
  • Predictions verified against numerical simulation of the 2-D SWEs

Free Access

How Eddies Gain, Retain, and Release Water: A Case Study of a Hokkaido Anticyclone

  • Pages: 2081-2096
  • First Published: 07 March 2018
Key Points

  • Lagrangian methodology is elaborated to document how mesoscale eddies gain, retain, and release water masses of different origin
  • We track the evolution of mesoscale eddies during the satellite-altimetry era propagating along the Japan and Kuril Trenches
  • The Hokkaido eddy is analyzed in detail in order to compare simulation results to observations

Free Access

Origins of Eddy Kinetic Energy in the Bay of Bengal

  • Pages: 2097-2115
  • First Published: 15 February 2018
Key Points

  • EKE generation in the east of Sri Lanka and the western BOB is dominated by oceanic internal instability
  • Wind forcing of ISOs contributes substantially to EKE in the northwest of Sumatra and the coastal rim of the BOB
  • Wind forcing induces EKE via both remote forcing of equatorial winds and local wind forcing within the BOB

Free Access

Intrusion Pattern of the Offshore Kuroshio Branch Current and Its Effects on Nutrient Contributions in the East China Sea

  • Pages: 2116-2128
  • First Published: 07 March 2018
Key Points

  • An obvious difference of P concentration gradient was observed in the Offshore Kuroshio Branch on ECS shelf in autumn
  • The higher concentrations of P likely came from deeper layer of Kuroshio subsurface water
  • This phenomenon might be attributed to the location change of Kuroshio Branch intrusion to ECS shelf

Free Access

Observation-Driven Estimation of the Spatial Variability of 20th Century Sea Level Rise

  • Pages: 2129-2140
  • First Published: 15 March 2018
Key Points

  • Regional sea level trends are computed using tide gauges and estimates of the structure of the processes contributing to sea level change
  • The regional sea level trends are optimized to agree with the tide gauges, providing an indication of the contribution of different sources
  • This study demonstrates the sensitivities of this regional trend map to current knowledge and uncertainty of the contributing processes

Free Access

An Inverse Model for Estimating the Optical Absorption and Backscattering Coefficients of Seawater From Remote-Sensing Reflectance Over a Broad Range of Oceanic and Coastal Marine Environments

  • Pages: 2141-2171
  • First Published: 20 February 2018
Key Points

  • An improved inverse reflectance model for estimating ocean inherent optical properties (IOPs) with no spectral assumptions was developed
  • Model evaluation with a synthetic data set indicates that algorithmic formulations are adequate, which results in good IOP retrievals
  • Satisfactory model performance is validated with extensive data sets of in situ measurements and a satellite-in situ match-up data set

Free Access

Turbulence Scaling Comparisons in the Ocean Surface Boundary Layer

  • Pages: 2172-2191
  • First Published: 07 March 2018
Key Points

  • Open ocean turbulence observations presented do not support commonly applied scaling approaches
  • An empirical scaling relationship based on wind and wave forcing is suggested for daytime conditions
  • When convection is important additional buoyancy forcing should be considered

Free Access

Uncertainties in Climatological Seawater Density Calculations

  • Pages: 2192-2212
  • First Published: 27 December 2017
Key Points

  • Based on Thermodynamic Equation of Seawater 2010, uncertainties in climatological seawater density calculations are quantified
  • Means distribution of density calculations' uncertainties is related to the correlation coefficient between Absolute Salinity and pressure
  • Results may provide valuable uncertainty information required for reliability considerations of ocean circulation and global climate models

Free Access

Pancake Ice Thickness Mapping in the Beaufort Sea From Wave Dispersion Observed in SAR Imagery

  • Pages: 2213-2237
  • First Published: 25 January 2018
Key Points

  • Sea ice thickness—we describe and thoroughly test a technique which derives thickness from wave dispersion changes
  • Pancake ice is the ice type concerned, in which waves propagate according to a viscous dispersion model
  • Synthetic aperture radar images enable the wavelength changes due to the ice to be measured

Free Access

Seasonal Variation of Barrier Layer in the Southern Ocean

  • Pages: 2238-2253
  • First Published: 16 February 2018
Key Points

  • The barrier layer in the Southern Ocean has a strong seasonal cycle with maximum amplitude exceeding 250 m in winter
  • Two areas with the most significant barrier layer are located south of Australia and in the southeastern Pacific Ocean
  • The barrier layer formation is due to shallow mixed layer caused by freshwater intrusion and deep isothermal layer by seasonal convection

Free Access

Dynamics of Gravity Currents in the Presence of Surface Waves

  • Pages: 2254-2273
  • First Published: 02 March 2018
Key Points

  • The front velocity is enhanced or decreased depending on the Lagrangian mass transport
  • Concentration is influenced by shear (interface) and orbital motion (core)
  • A simple linear model can predict front velocity with and without waves

Free Access

Patterns of Vertical Velocity Induced by Eddy Distortion in an Ocean Model

  • Pages: 2274-2292
  • First Published: 07 March 2018
Key Points

  • Eddies from the East Australian Current have alternating upward and downward cells in their interior
  • Upward and downward cells are induced by change in eddy isotropy
  • Change in sea level anomaly is a good proxy for change in eddy isotropy

Free Access

Wave Attenuation and Gas Exchange Velocity in Marginal Sea Ice Zone

  • Pages: 2293-2304
  • First Published: 12 March 2018
Key Points

  • Reduction of air-sea gas exchange in limited waters
  • Sea ice as enhancers or inhibitors of effective gas exchange in marginal sea ice zones
  • Sea ice role in parameterization of gas exchange based on turbulence kinetic energy dissipation

Free Access

On the Use of Satellite Altimetry to Detect Ocean Circulation's Magnetic Signals

  • Pages: 2305-2314
  • First Published: 12 March 2018
Key Points

  • Sea surface height-based magnetic fields are derived using the geostrophic approximation
  • The derived fields correlate well with the main features of the ocean circulation's magnetic signal
  • A one-time calibration is advised to further improve the estimate's explained variance