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Seasonal Variability of Phytoplankton Biomass Revealed by Satellite and BGC-Argo Data in the Central Tropical Indian Ocean

  •  1 October 2022

Key Points

  • The phytoplankton biomass in 0–10 m decreased (increased), while that in 50–100 m increased (decreased) during February–May (June and July)

  • The deep vertical mixing drove the supply of both nutrients and phytoplankton from the subsurface to support near-surface blooms

  • The intensity of subsurface blooms depended on the modulation of the thermocline depth by wind-induced upwelling

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Relating a Large-Scale Variation of Waves in the Indian Ocean to the IOD

  •  30 September 2022

Key Points

  • Although swells from the Southern Ocean propagate northward for a long distance, the zonal surface Stokes drift is related to the wind waves

  • Stokes drift plays a positive role in maintaining the zonal stability of sea surface temperature at low latitudes in the Indian Ocean

  • Wave transport is of the same order of magnitude as Ekman transport and its zonal component is greater for more than 80% of the sea areas

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Issue Information

  •  29 September 2022
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A Directional Decomposition Method to Estimate the Reflection and Transmission of Nonlinear Internal Waves Over a Slope

  •  29 September 2022

Key Points

  • A directional decomposition method is proposed to estimate the reflection, transmission, and dissipation of nonlinear internal waves (NLIWs) over a slope in numerical simulations

  • The rate of reflection (dissipation) of energy for the shoaling NLIWs is much lower (higher) than that for the shoaling internal tides over the same slope

  • About 60% of shoaling IW energy is reflected due to the blocking effect of the Imperieuse Reef around the Rowley Shoals

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Effects of Increasing the Category Resolution of the Sea Ice Thickness Distribution in a Coupled Climate Model on Arctic and Antarctic Sea Ice Mean State

  •  29 September 2022

Key Points

  • Higher resolution of the sea ice thickness distribution increases simulated Arctic sea ice thickness, with little change in Antarctic sea ice

  • The impact has a bigger effect on dynamic processes than thermodynamic processes

  • Comparison with subgrid-scale thickness observations from ICESat-2 suggests targeting ridging for improvement

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Ocean Variability Beneath the Filchner-Ronne Ice Shelf Inferred From Basal Melt Rate Time Series

  •  28 September 2022

Key Points

  • Melt rate time series from Filchner-Ronne Ice Shelf show multiple time scales of variability with a character that varies spatially

  • Inter-annual melt rate variations driven by sea-ice concentration anomalies are limited to a pathway through the central Ronne Ice Shelf

  • Existing melt rate estimates from satellite data dramatically overestimate the amplitude of inter-annual melt rate variability

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Slantwise Convection in the Irminger Sea

  •  28 September 2022

Key Points

  • Down-front wind buoyancy forcing is stronger than heat loss buoyancy forcing in the western Irminger Sea

  • We observe a subsurface ocean response to down-front winds consistent with slantwise convection

  • Slantwise convection may mix waters to several times the conventionally defined mixed layer depth in this region

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Regime Shift in Annual Nitrate Concentration in the Upper Southern Chukchi Borderland Responded to the Westward Shift of the Beaufort Gyre

  •  26 September 2022

Key Points

  • The westward movement of the Beaufort Gyre drives the enhanced westward component of ocean currents in the southern Chukchi Borderland

  • With the changed current, westward nitrate flux in the southern Chukchi Borderland increases, while northward flux decreases

  • Nitrate concentration in the upper southern Chukchi Borderland has been shifting from a high level to a low level since 2009

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Coupled Atmosphere–Ocean Variations on Timescales of Days Observed in the Western Tropical Pacific Warm Pool During Mid-March 2020

  •  26 September 2022

Key Points

  • Temporal warming of tropical Pacific warm pool was related to enhanced sensitivity of mixed layer temperature to solar-radiation heating

  • Wind intensification due to atmospheric inertia-gravity waves enhances upward latent heat flux and causes diurnal dancing of heavy rainfall

  • Changes of lower troposphere stratification and wind speed alter coupling strength between the atmosphere and ocean variations

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Gas Fluxes and Steady State Saturation Anomalies at Very High Wind Speeds

  •  25 September 2022

Key Points

  • Air sea fluxes of noble gases initially increase as wind speed increases from 20 to 35 m s−1 but then level off at higher speeds

  • Steady state saturation anomalies are more strongly correlated with bubble volume and significant wave height than with wind speed

  • Invasion fluxes are larger in magnitude than evasion fluxes under similar conditions

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Recent Changes of Phytoplankton Bloom Phenology in the Northern High-Latitude Oceans (2003 – 2020)

  •  7 October 2022

Key Points

  • Satellite data show a significant increase in double blooms of phytoplankton north of 50°N, particularly from 2016 to 2020

  • The correlation of double blooms with mixed layer depth and sea surface temperature is dependent on latitude and season

  • From 2016 to 2020, the interval between peaks of single PIC and Chl a blooms shortened in the subpolar North Pacific Ocean

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Phase-resolved modeling of wave interference and its effects on nearshore circulation in a large ebb shoal-beach system

  •  7 October 2022

Key Points

  • A time-domain Boussinesq model reproduced wave interference observed at Ocean Beach, CA

  • The model reveals small-scale persistent fingering structures in the wave height distribution tied with nearshore flow structures

  • Alongshore-varying wave breakers caused by wave interference are the source of vorticity generation, inducing energetic vortex eddies nearshore

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Under-ice hydrography of the La Grande River plume in relation to a ten-fold increase in wintertime discharge

  •  6 October 2022

Key Points

  • Despite higher discharge, and a much larger overall region of freshwater influence, the core area of the plume (salinity <5) was not significantly larger when compared to studies in the 1980s

  • The plume’s northward extent is determined mainly by coastal geometry and the landfast ice narrowing at 35 km from the river mouth

  • The plume’s influence on eelgrass habitats depends upon discharge, proximity to the river mouth and the degree of protection offered by islands

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Characteristics and drivers of marine heatwaves in the western equatorial Indian Ocean

  •  6 October 2022

Key Points

  • Marine heatwaves in the western equatorial Indian Ocean (WEIO) have significant interannual variability related to the Indo-Pacific climate

  • Marine heatwaves in the WEIO are mainly driven by westward-propagating downwelling equatorial Rossby waves and off-equatorial Rossby waves

  • The frequency and duration of marine heatwaves exhibited significant increasing trends in the WEIO from 1982 to 2020

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Dispersion of particle-reactive elements caused by the phase transitions in scavenging

  •  6 October 2022

Key Points

  • Novel scavenging mechanism due to the reversible phase transition results in apparent diffusivity which surpasses the ocean diffusivity

  • In the well-ventilated Eastern Mediterranean, the ratio of the reduced form to the oxidized form of 239,240Pu was approximately 0.22-0.24

  • The 239,240Pu profile in the Eastern Mediterranean has one maximum, whereas in the anoxic Black Sea it has two maximums

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Dispersion processes in weakly dissipative tidal channels

  •  5 October 2022

Key Points

  • A large-scale physical model is used to study tidal dispersion and the flood-macrovortices generated at the inlet

  • The Lagrangian integral scale and the corresponding dispersion coefficients attain a constant value for increasing friction parameter

  • Dispersion processes are dominated by local dynamics for particle separations larger than the typical tidal inlet length scale

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Sequential Bayesian update to detect the most likely tsunami scenario using observational wave sequences

  •  5 October 2022

Key Points

  • A sequential Bayesian update scheme for the detection of the most likely tsunami scenario using proper orthogonal decomposition is presented

  • Two case studies targeting the Nankai Trough are carried out to demonstrate the procedure and capabilities of the proposed method

  • The most likely tsunami scenarios are detected with 7 minutes of observational wave data from 71 synthetic gauge points

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Global trends in marine heatwaves and cold spells: The impacts of fixed versus changing baselines

  •  5 October 2022

Key Points

  • It is argued that marine heatwaves (MHW) and cold spells (MCS) should be defined relative to sea surface temperature (SST) adjusted for climate change

  • When a linear SST climate signal is removed, 1982-2021 MHW and MCS show non-significant trends except in the tropics and high latitudes

  • Trends in the tropics reflect ENSO trends; trends at high latitudes reflect North Atlantic and Atlantic Multidecadal Oscillation trends

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Measuring Estuarine Total Exchange Flow from Discrete Observations

  •  5 October 2022

Key Points

  • A threshold of 1-5 sample depths was needed to measure the exchange flow

  • Most ( > 90%) of the exchange flow magnitude was captured by 3-4 moorings spread across the channel

  • The exchange volume transport was more sensitive than salinity to the sampling resolution

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Small-scale spatial variations of air-sea heat, moisture, and buoyancy fluxes in the tropical trade winds

  •  5 October 2022

Key Points

  • Autonomous piloted and Lagrangian drifting platforms measured air-sea properties and fluxes in the northwestern tropical Atlantic

  • Sensible heat, latent heat, and upward buoyancy flux varied by as much as 10, 50, and 10 Wm−2 across 10-100 km SST gradients

  • Spatial SST gradients were a leading cause of sensible heat flux variability, but humidity fluctuations largely modulated latent heat flux

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EN4: Quality controlled ocean temperature and salinity profiles and monthly objective analyses with uncertainty estimates

Key Points

  • EN4 dataset of quality-controlled temperature and salinity profiles is described
  • Dataset covers 1900 to present and includes monthly objective analyses
  • A novel method is presented to estimate uncertainty in the objective analyses

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A Global Perspective on Microplastics

Key Points

  • The sources, behavior, fate, and effects of microplastics are inexplicably tied to those of their plastic product and macrodebris precursors, as well as the nanoplastics into which they fragment
  • Microplastic sampling and characterization methods are evolving, but their inadequacies still hamper efforts to evaluate the true extent of their presence and consequences in the built and natural environments
  • Microplastics are a global/multimedia phenomenon; hence, they cannot be adequately understood, or related concerns resolved, in the context of the marine environment alone or a single discipline

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The Role of the New Zealand Plateau in the Tasman Sea Circulation and Separation of the East Australian Current

Key Points

  • EAC separation latitude shifts south 1.1 degrees when the New Zealand submarine platform is completely removed and Tasman Sea is leveled
  • The presence of the New Zealand submarine platform weakens the EAC extension and strengthens the Tasman Front
  • Meridional gradients in the basin-wide wind stress curl are not the sole factor determining the mean latitude of EAC partial separation

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Submesoscale Sea Ice-Ocean Interactions in Marginal Ice Zones

Key Points

  • Energetic submesoscale ocean variability forms at marginal ice zones due to mixed-layer instabilities of ice-edge meltwater fronts
  • Mechanical sea ice-ocean interactions trap sea ice in cyclonic eddies and filaments—regions with dramatically enhanced ocean heat fluxes
  • The strength of submesoscale sea ice-ocean coupling is expected to increase with thinning of Arctic sea ice and marginal ice zone expansion

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North Atlantic Ocean Internal Decadal Variability: Role of the Mean State and Ocean-Atmosphere Coupling

Key Points

  • The AMOC and AMV decadal variability can emerge from a self-sustained oceanic mode based on coupled model results
  • Increasing atmospheric resolution decreases the oceanic variability due to mean state changes
  • Atmosphere-ocean coupling causes a moderate increase of the AMOC variability

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Observation of rogue wave holes in a water wave tank

Key Points

  • Experimental generation of rogue wave holes
  • Rogue waves holes within the framework of the nonlinear Schrodinger equation
  • Rogue wave holes modeled by the Peregrine soliton

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Intensification and poleward shift of subtropical western boundary currents in a warming climate

Key Points:

  • WBCs are strengthening and shifting toward poles under global warming
  • Three types of independent data sets are included
  • Several coupled parameters are used to identify the WBCs dynamics

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Mesoscale resolution capability of altimetry: Present and future

Key Points

  • A global analysis of wavenumber spectra of Sea Surface Height determines the mesoscale resolution capability of altimeter missions
  • The future 2-D mesoscale resolution capability of the SWOT altimeter mission is predicted using a simulated error level

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Mixed layer heat and salinity budgets during the onset of the 2011 Atlantic cold tongue

Key Points

  • Atlantic cold tongue development from May to July 2011 was examined
  • Diapycnal mixing is key process for cooling in western cold tongue region
  • Zonal advection is main contributor to mixed layer salinity changes

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Biogeochemical sensor performance in the SOCCOM profiling float array

Key Points

  • Biogeochemical sensors on profiling floats require careful adjustments for sensor calibration error and drift
  • After adjustment, biogeochemical sensor data can approach the accuracy found in large data sets such as GLODAP
  • Adjusted sensor data accuracy has relatively little degradation over the many years a profiling float operates

Plain Language Summary

The ocean science community must move toward greater use of autonomous platforms and sensors if we are to extend our knowledge of the effects of climate driven change within the ocean. Essential to this shift in observing strategies is an understanding of the performance that can be obtained from biogeochemical sensors on platforms deployed for years and the procedures used to process data. This is the subject of the manuscript. We show the performance of oxygen, nitrate, pH, and bio-optical sensors that have been deployed on robotic profiling floats in the Southern Ocean for time periods up to 32 months.

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