751 articles
Oceanographic time-series cruise programs
Oceanographic time-series cruise programs are recurring shipboard expeditions that occupy the same deep-ocean station on a monthly schedule to measure water-column physics, chemistry, and biology over decades.
Oceanography
Oceanography, also called ocean science or marine science, is the study of the ocean, drawing on physics, chemistry, geology, and biology to cover seawater, marine life, currents, and the seafloor.
Offshore groundwater
Offshore groundwater is low-salinity water stored in sediments and rocks below the seafloor, first documented off Florida in the 1960s and estimated at about 1 million cubic kilometers globally.
Ogallala Aquifer
The Ogallala Aquifer, formally the High Plains aquifer, is a groundwater system underlying about 174,000 square miles of the Great Plains in eight states, supplying about 30 percent of US irrigation groundwater.
Oligotrophication
Oligotrophication, also called re-oligotrophication, is the decline of nutrient concentrations and productivity in an aquatic ecosystem, most often a deliberate result of cutting nitrogen and phosphorus inputs to a formerly eutrophic lake.
Oliver Fringer
Oliver Fringer is a Stanford professor who develops numerical models of coastal ocean, river, lake, and estuary dynamics, and received a PECASE award in 2008.
Ombrotrophic
Ombrotrophic describes a peatland, typically a bog, that receives all its water and dissolved nutrients from rain and snow, with no groundwater or runoff from mineral soil.
Origin of water on Earth
The origin of water on Earth, also called the origin of the oceans, is the unsolved question of how Earth acquired its water, with asteroids the leading source.
Outburst flood
An outburst flood is a sudden, large release of water from a natural dam, such as a glacier-dammed lake, producing a flood far larger than the river's normal flow.
Overexploitation of groundwater
Overexploitation of groundwater, also called groundwater overdraft or aquifer overexploitation, is the extraction of water from aquifers faster than they are replenished by recharge, causing declining groundwater storage worldwide.
Overturn
Overturn: in oceanography, the mixing of stratified water due to density instability, and the related global overturning circulation (thermohaline circulation, AMOC) that sinks dense polar water and redistributes heat, salt, and carbon worldwide.
Overturning in the Subpolar North Atlantic Program
The Overturning in the Subpolar North Atlantic Program (OSNAP) is an international program measuring the Atlantic meridional overturning circulation with a moored array since 2014.
Oxygen minimum zone
An oxygen minimum zone (OMZ) is a persistent ocean layer, about 100 to 1,500 m deep, where dissolved oxygen falls far above and below levels of nearby waters, and zones are expanding as the ocean warms.
Pacific Tsunami Warning Center
The Pacific Tsunami Warning Center (PTWC) is a National Weather Service facility at ʻEwa Beach, Hawaii, established in 1949 to warn of tsunamis across the Pacific and Caribbean.
Paleolimnology
Paleolimnology is the study of lake and wetland sediments, using physical, chemical, and biological proxies in dated sediment cores to reconstruct past lake, catchment, and climate conditions over decades to millennia.
Palmer Station
Palmer Station is a U.S. year-round Antarctic research station on Anvers Island, off the Antarctic Peninsula, operated by the National Science Foundation and commissioned in 1968.
Panta Rhei (hydrology)
Panta Rhei, Greek for "everything flows," was the second Scientific Decade of the International Association of Hydrological Sciences, running from 2013 to 2022 to study change in hydrology and society.
ParFlow
ParFlow (PARallel FLOW) is an open-source, parallel, integrated hydrology model that simulates surface and subsurface water flow with land surface processes, initiated at Lawrence Livermore National Laboratory in the mid-1990s.
Parshall flume
The Parshall flume is an open-channel flow-measuring structure invented by Ralph Parshall in 1922, which converts upstream water depth into discharge and is widely used for irrigation and wastewater.
Patricia Dalyander
Patricia ("Soupy") Dalyander is an American physical oceanographer known for modeling how waves and currents move sand, oil, and barrier islands along the Gulf of Mexico coast, and a 2019 PECASE recipient.
PCR-GLOBWB
PCR-GLOBWB (PCRaster Global Water Balance) is an open-source global hydrology and water resources model developed at Utrecht University in the Netherlands, simulating soil moisture, groundwater, and human water use at daily time steps.
Peak water
Peak water is the concept that freshwater availability or use can rise to a maximum and then decline, formalized by Peter Gleick and Meena Palaniappan in 2010.
Peat subsidence
Peat subsidence is the lowering of the land surface when drained peat soils shrink, consolidate, compact, and oxidize, typically at rates of millimeters to centimeters per year.
Peatland rewetting
Peatland rewetting is the cessation of drainage and restoration of high groundwater levels in degraded peatlands, typically by ditch blocking, to stop carbon dioxide emissions from dried-out peat soils.
Pelagic zone
The pelagic zone, also called the open ocean, is the entire water column of the sea, away from the bottom and shore, and Earth's largest habitat.
Penetrative convection
Penetrative convection is a form of turbulent convection in which surface cooling drives plumes that overshoot into stratified water below, entraining it and deepening a lake's mixed layer.
Penman–Monteith equation
The Penman–Monteith equation estimates evapotranspiration from standard weather variables, combining surface energy balance with aerodynamic vapor transfer; FAO-56 adopted it as its sole standard in 1998.
Perched water table
A perched water table is a local zone of saturation sitting above the regional water table, held there by a low-permeability layer and separated from the main groundwater by unsaturated soil.
Permanent wilting point
The permanent wilting point (PWP) is the soil water content at which plants wilt irrecoverably, conventionally defined as water held at −1500 kPa, and with field capacity it bounds plant-available water.
Permeability (porous media)
Permeability, also called intrinsic permeability, is the capacity of a rock or porous material to transmit a fluid. It governs groundwater flow in aquifers and oil movement toward wells.