Environment, Ocean Science and the Natural World

Coastal processes, sea-level, cryosphere and ocean observation science glossary

The margins of the ocean, the changing volume of the sea, the frozen ocean, and the technologies that observe them: longshore sediment transport, estuarine circulation and storm surge, relative versus eustatic sea-level change, sea-ice thermodynamics and ice charting, marine acoustics and the SOFAR channel, and ocean remote sensing by altimetry, scatterometry, and ocean color. Bodies include the IPCC, USGS, NSIDC, SCAR, NASA, ESA, and Copernicus Marine.

230 defined terms.

A

Ablation (Glacier): Loss of glacier mass through melting, sublimation, or calving.
Accretion: Build-up of sediment forming shoreline progradation.
Active Sonar: Sonar emitting pulses and listening for echoes.
Advection of Heat (Cryosphere): Ocean heat transport melting ice shelves.
Aerosol Optical Thickness (Ocean Color): Atmospheric correction parameter in ocean color retrievals.
Airborne Lidar: Laser scanning from aircraft used in coastal topography.
Aliasing (Altimetry): Misrepresentation of high-frequency signals by altimeter sampling.
Altimetry: Measurement of sea surface height using radar from satellites.
AMSR (Advanced Microwave Scanning Radiometer): Satellite microwave radiometer used for sea ice and SST.
ANSCATT (Antarctic Bottom Scatter): Not standard.
Antarctic Bottom Water Formation: Process forming dense water around Antarctica.
Antarctic Sea Ice: Sea ice surrounding Antarctica, exhibiting strong seasonal cycle.
Aragonite Saturation Horizon Shoaling: Vertical rise of corrosive waters under acidification.
Arctic Amplification: Faster warming of the Arctic relative to the global mean.
Arctic Oscillation: Climate mode describing surface pressure patterns in the Arctic.
AUV (Autonomous Underwater Vehicle): Untethered submersible carrying sensors.

B

Backscatter: Acoustic or radar energy returning toward the source.
Baltic Sea Level Trend: Distinct regional sea-level pattern influenced by glacial rebound.
Bar (Coastal): Submerged accumulation of sand parallel to shore.
Barrier Island: Long offshore depositional bar parallel to a coast.
Beach Profile Survey: Periodic surveying of beach elevation.
Beach Rotation: Cyclic shoreline change between beach ends.
Berm Crest: Top edge of a beach berm.
Big Floe: Sea ice floe between 500 and 2,000 meters across.
Bjerknes Centennial Antarctic Sea Ice Models: Research models of sea ice variability.
BOAS (Buoy Ocean Acoustic Sensor): Acoustic mooring sensor.
Brunt Ice Shelf: Antarctic ice shelf monitored for calving.
Buoy Network: Network of moored or drifting buoys.
Buoyancy Driven Glider: Underwater glider using buoyancy and wings for propulsion.

C

Cable Observatory: Seafloor observatory powered and connected by submarine cable.
Caesium Isotope Tracer: Tracer of ocean circulation following nuclear releases.
Calving (Glacier): Detachment of icebergs from glaciers or ice shelves.
Carbonate Pump: Component of the biological pump involving calcium carbonate.
CERSAT: French center processing satellite sea ice data.
CFOSAT: China-France Oceanography Satellite measuring waves and winds.
Chlorophyll Front: Boundary between water masses with different chlorophyll content.
CICE: Los Alamos sea ice model used in coupled climate models.
Cliff Erosion: Retreat of coastal cliffs.
Coastal Squeeze: Loss of intertidal habitat between rising seas and fixed defenses.
Coastal Vulnerability Index (CVI): Composite index ranking coastal exposure to sea-level rise.
Coastal Wetland Loss: Decline in mangroves and saltmarshes from various pressures.
Cold Pole: Region of long-term lowest temperatures, such as East Antarctic Plateau.
Common Era: Time period used in sea-level reconstructions.
Copernicus Marine Service (CMEMS): European operational marine forecasting service.
Cryosat-2: ESA satellite mission measuring ice thickness using radar altimetry.
Cryosphere: All frozen water on Earth, including sea ice, glaciers, and ice sheets.

D

DAC (Dynamic Atmospheric Correction): Correction applied to altimetry for atmospheric pressure and wind effects.
Deep-Tow Sonar: Sonar towed close to the seabed for high resolution imaging.
Delft3D: Open-source modeling suite for hydrodynamics, morphology, and water quality.
Deltares: Dutch institute developing tools such as Delft3D for coastal modeling.
DEM (Digital Elevation Model): Gridded representation of surface topography.
Diurnal Tide Gauge: Tide gauge resolving diurnal variations.
Doppler Scatterometer: Sensor like WaCM measuring surface currents.
Downwelling Surface Solar Irradiance: Solar radiation reaching the sea surface.
Drift Ice: Sea ice not attached to the shore, drifting with winds and currents.
Drifting Buoy: Free-drifting buoy reporting SST and SLP.
Drogue (Drifter): Subsurface element ensuring a drifter follows water at a specified depth.
Drone Bathymetry: Use of UAVs with lidar or photogrammetry for shallow bathymetry.

E

ECMWF Reanalysis 5 (ERA5): Latest ECMWF global reanalysis covering since 1940.
Eddy Covariance Flux: Direct measurement of turbulent fluxes across the sea surface.
EM Bird: Helicopter-borne electromagnetic sensor for sea ice thickness.
Ensemble Forecast: Multiple model runs sampling forecast uncertainty.
EOS-Aura: NASA satellite carrying atmospheric chemistry instruments.
EROS Data Center: USGS center distributing remote sensing data.
ESA: European Space Agency.
EUMETSAT: European satellite organization operating Meteosat and Metop.
Eustatic Rise: Globally averaged sea-level rise.
Expendable Probe: Single-use ocean profiling probe such as XBT.

F

Fast Ice: Sea ice frozen to the shore.
Fetch Limited Sea: Wave field constrained by limited fetch.
Field of View (Satellite): Solid angle observed by a sensor.
FIFE (Field Intensive Field Experiment): Generic term for field campaigns.
First-Year Ice: Sea ice that has not survived a melt season.
Fjord Mooring Network: Set of moored instruments monitoring fjord circulation.
Floe: Individual piece of sea ice.
Forecast Skill: Quantitative measure of forecast accuracy.
FORWARD Model: Generic ocean acoustic forward model term.
Freeboard (Sea Ice): Height of ice surface above waterline, used to derive thickness.
Frontal Eddy: Mesoscale eddy spawned along ocean fronts.
Frost Flower: Ice crystals forming on new sea ice with high salinity.
Future Sea Level Allowance: Engineering planning factor accounting for projected sea-level rise.

G

Geodetic GPS Tide Gauge: Tide gauge whose benchmark position is monitored by GPS.
GFO (Geosat Follow-On): US Navy altimetry satellite.
Glacial Isostatic Adjustment (GIA): Crustal response to changes in ice load.
Glider: Buoyancy-driven autonomous underwater vehicle.
GLORYS: Mercator Ocean global ocean reanalysis.
GMSL (Global Mean Sea Level): Globally averaged sea level.
GOCE: ESA Gravity field and steady-state Ocean Circulation Explorer mission.
GRACE / GRACE-FO: Gravity Recovery and Climate Experiment missions measuring mass changes.
Grounding Line: Junction where a glacier transitions to floating ice.
GSM (Greenland Sub-Glacial Melt): Subglacial discharge to fjords.
Gulf of Maine Warming: Rapid warming of a regional sea important to fisheries.

H

Halocline Layer (Arctic): Strong Arctic salinity gradient insulating sea ice from warmer deep water.
HF Radar: High-frequency coastal radar measuring surface currents.
High Tide Flooding: Recurrent coastal flooding at predictable high tides, also called sunny day flooding.
HIRS (High-Resolution Infrared Sounder): Satellite atmospheric sounder.
HUDDLE Test: Field comparison test for autonomous platforms.
Hydrate Stability Zone: Pressure-temperature window for methane hydrate stability.
Hydrographic Reanalysis: Long-term reconstruction of ocean state from hydrographic data.
Hydrophone: Underwater microphone for acoustic measurements.

I

Ice Camp: Temporary station on sea ice supporting research.
Ice Charting: Operational mapping of sea ice for navigation.
Ice Class: Hull classification for ships operating in ice.
Ice Shelf: Floating extension of an ice sheet.
Ice Tongue: Long, narrow seaward extension of a glacier.
ICESat-2: NASA laser altimetry mission for ice surface elevation.
In Situ Observation: Direct measurement at a location.
Infrasound (Marine): Low-frequency sound used to monitor ice and marine events.
InSAR (Interferometric SAR): Technique using radar phase to measure surface deformation.
Iridium-Linked Buoy: Buoy reporting via Iridium satellites.
Isostatic Rebound: Crustal uplift after removal of an ice load.

J

Jason-3: NOAA-CNES altimetry satellite measuring sea surface height.
Jet Drilling (Ice): Hot water drilling through ice shelves for instrument deployment.

K

K-Band Radiometer: Microwave instrument used for atmospheric and SST retrievals.
Kelvin Wave (Coastal): Trapped wave traveling along a coastline with rotation effects.
Knot (Speed): Unit of speed equal to one nautical mile per hour, used in observation reporting.

L

Lagrangian Drifter Network: Set of free drifting floats or buoys.
Lake Effect (Cryosphere): Polynyas behaving thermally like lakes.
Land-Fast Ice: Sea ice attached to the coast.
Larsen Ice Shelf: Antarctic ice shelf whose recent disintegrations are widely studied.
Last Glacial Maximum (LGM): Period of maximum global ice extent around 21,000 years ago.
Lead (Sea Ice): Linear opening in sea ice cover.
Lidar Altimetry: Satellite laser altimetry as on ICESat-2.
Long-Term Ecological Research (LTER): Programs maintaining decadal observations of ecosystems.
Longshore Current: Wave-driven current parallel to shore in the surf zone.
Longshore Sediment Transport: Sediment transport along the shore by waves and currents.

M

Marine Acoustics: Study of sound in seawater.
Marine Heatwave Category: Hobday et al. classification scheme for marine heatwaves.
Median Floe Size: Statistical measure of sea ice floe sizes.
Mercator Ocean International: French organization producing ocean analyses for CMEMS.
Meridional Heat Transport: North-south transport of heat by ocean and atmosphere.
MetOp Satellites: EUMETSAT polar-orbiting satellites carrying ASCAT and others.
Microwave Radiometer: Passive sensor measuring brightness temperatures.
Mid-Latitude Coastal Hazard: Coastal risk from extratropical storms.
Mode-S EHS: Aircraft data assimilated in weather forecasts.
MODIS: NASA Moderate Resolution Imaging Spectroradiometer on Terra and Aqua.
Multi-Beam Echo Sounder Time Series: Repeated bathymetric mapping for change detection.
Multi-Year Ice: Sea ice that has survived at least one melt season.

N

NASA Worldview: NASA browsing tool for satellite imagery.
National Snow and Ice Data Center (NSIDC): US data center for cryospheric data.
NDBC Buoy: NOAA National Data Buoy Center moored station.
Nearshore Bathymetric Profile: Cross-shore depth profile near the coast.
NEMO Ice Module: LIM sea ice component of the NEMO ocean model.
NetCDF: Common data format used for ocean and atmospheric datasets.
NIWA: National Institute of Water and Atmospheric Research, New Zealand.
NOAA NESDIS: NOAA's satellite data service.
Nodal Cycle Sea Level Modulation: 18.6-year tidal modulation of sea-level extremes.
Nonlinear Sea Level Rise: Acceleration of sea-level rise beyond linear trends.

O

Ocean Acoustic Tomography: Technique using sound travel times to infer ocean structure.
Ocean Color: Visible light reflectance used to estimate phytoplankton and CDOM.
Ocean Heat Content (Anomaly): Departure of OHC from a reference period.
Ocean Observatories Initiative (OOI): US NSF program of cabled and global ocean observatories.
Ocean Reanalysis: Long-term ocean state estimate combining models and observations.
OCO-2/OCO-3: NASA satellites measuring atmospheric CO2.
Open Polynya: Polynya kept open by ocean heat flux from below.

P

Pancake Ice: Round pieces of sea ice formed in turbulent water.
Passive Acoustic Monitoring: Listening with hydrophones to monitor marine life and noise.
Pelagic Habitat Mapping: Mapping of water-column habitats.
Permafrost (Subsea): Permanently frozen seabed sediment on shallow Arctic shelves.
Photic Zone: Surface layer with sufficient light for photosynthesis.
Pinger: Acoustic device used in fisheries and observations.
Polar Code: Adopted under SOLAS XIV and MARPOL; complements Article 234 jurisdiction.
Polar Front (Cryosphere): Boundary between polar and subpolar water masses.
POLARIS Rating: IMO operational rating for ships in polar waters.
Pole and Drift Sled: Polar field equipment for surface observations.
Polynya: Persistent open water area within sea ice.
Profiling Float: Subsurface float that cycles vertically for measurement.

Q

Quasi-Stationary Front: Ocean front persisting in a region for extended periods.
QuikSCAT: NASA scatterometer mission measuring sea surface winds.

R

R/V (Research Vessel): Ship dedicated to scientific research.
Radar Altimeter: Satellite instrument measuring sea surface height by radar.
Radarsat Constellation Mission (RCM): Canadian SAR satellite constellation.
Radial HF Radar Data: Component data from HF radar.
Reanalysis (Ocean): Reconstruction of past ocean state from observations and models.
Reference Frame ITRF: International Terrestrial Reference Frame used for geodesy.
Remote Sensing Reflectance (Rrs): Ocean color product related to water-leaving radiance.
Return Period: Average interval between events of a specified magnitude.
Ross Sea Polynya: Major polynya in front of the Ross Ice Shelf.
ROV (Remotely Operated Vehicle): Tethered underwater robot.
RTK Coastal Survey: Real-time kinematic GPS surveying of coasts.

S

Saildrone: Wind- and solar-powered uncrewed surface vehicle.
SAR (Synthetic Aperture Radar): Satellite radar producing high-resolution imagery.
Scatterometer: Microwave radar measuring backscatter to retrieve surface winds.
Sea Ice Drift: Movement of sea ice driven by winds and currents.
Sea Ice Extent: Total area where ice concentration exceeds a threshold, usually 15 percent.
Sea Ice Thickness: Vertical thickness of sea ice.
Sea Level Budget: Decomposition of sea-level change into mass and steric components.
Sea Level Reconstruction: Synthesis of tide gauge and altimetry data over decades.
SeaBED AUV: Class of survey AUVs developed at WHOI.
Sentinel-3: Copernicus satellite series carrying altimetry and ocean color sensors.
Sentinel-6 Michael Freilich: Successor to Jason altimetry satellites.
Shelf Slope Cascade: Density-driven flow descending from the shelf to the slope.
Ship-Based Observation: In situ observation made from research and merchant ships.
Significant Wave Height (Climatology): Long-term statistics of significant wave height.
SMAP (Soil Moisture Active Passive): NASA L-band mission also providing sea surface salinity.
SMOS (Soil Moisture and Ocean Salinity): ESA L-band radiometer mission.
SOFAR Channel: Sound Fixing And Ranging channel where sound travels long distances.
Sonar: Sound navigation and ranging device.
Soundscape: Combination of biological, geophysical, and anthropogenic sounds.
Storm Surge: Abnormal sea level rise driven by a storm's winds and pressure.
Storm Tide: Combined storm surge and astronomical tide.
Subsea Permafrost: Permanently frozen seabed in shallow Arctic shelves.
Surface Wave Spectrum (Operational): Operational wave spectra from models like WAVEWATCH III.
SWOT: Surface Water and Ocean Topography mission providing two-dimensional sea surface height.

T

Telemetry: Remote transmission of data from sensors.
Tethered Profiler: Instrument that profiles up and down a mooring wire.
Tide Gauge Network: Global or regional array of tide gauges.
Tidewater Glacier: Glacier terminating in the ocean.
TOPEX/Poseidon: Pioneering NASA-CNES altimetry mission.
Total Sea Level (TSL): Sum of tide, surge, and mean sea level.
Tsunameter: Bottom pressure sensor in the DART system.
Tsunami Buoy: Surface buoy relaying DART data.

U

Uncrewed Surface Vehicle (USV): Autonomous surface vessel for observation.
Underwater Acoustic Channel: Propagation environment for acoustic signals.
Underway pCO2 System: Continuous shipboard measurement of surface pCO2.
Upper Ocean Heat Content (0-300 m): Heat content of the upper 300 meters of the ocean.

V

Validation Site: Reference site for assessing satellite product accuracy.
VIIRS: Visible Infrared Imaging Radiometer Suite on NOAA satellites.
VOS (Voluntary Observing Ship): Merchant ship voluntarily providing weather observations.

W

WAVEWATCH III: NOAA third-generation wave model.
WCRP: World Climate Research Programme.
Weddell Sea Bottom Water: Dense water mass formed in the Weddell Sea.
Wireline Profiler: Profiler that crawls up and down a mooring cable.
WMO Marine Climatological Summary: Summary of marine meteorological observations.

X

XBT Transect: Repeated XBT profile lines collected from ships of opportunity.
XSAT (Expendable Salinity Sensor): Probe for measuring near-surface salinity.

Y

Year-to-Year Variability: Interannual variability captured by observation networks.
Yellow Sea Cold Water Mass: Subsurface cold water mass in the Yellow Sea.

Z

Zenith Total Delay (Marine GPS): Tropospheric delay parameter from GPS used in atmospheric studies.
Zonal Wave Pattern: East-west pattern in atmospheric or oceanic fields.

Explore the Environment, Ocean Science and the Natural World portal