Cryosphere, Ocean Circulation, and Hydrosphere Systems

Vocabulary practice flashcards covering the components of the cryosphere, deep and surface ocean circulation dynamics, paleoecological evidence, and the terrestrial hydrosphere.

Cryosphere

The component of the Earth system consisting of all frozen water, including continental ice sheets, mountain glaciers, sea ice, lake and river ice, seasonal snow cover, and permafrost.

Snow

Precipitation consisting of ice crystals formed directly in clouds through the combination of water vapor, cold temperatures, and a mineral or organic condensation nucleus.

Global Seasonal Snow Cover

The surface area of snow extent across the globe, fluctuating seasonally from $2\text{--}4\text{ million km}^2$ in Northern Hemisphere summer (minimum in August) to $45\text{--}47\text{ million km}^2$ in winter (maximum in January).

Grounding Line

The boundary beneath an ice sheet or glacier where the grounded ice resting on bedrock detaches and begins floating on ocean water as an ice shelf.

Permafrost

Subsurface soil, sediment, or rock that remains continuously frozen at or below $0^\bot\circ\text{C}$ ($32^\bot\circ\text{F}$) for at least two consecutive years.

Active Layer

The uppermost layer of soil above permafrost that undergoes seasonal freezing in the winter and thawing in the summer.

Talik

A patch, layer, or body of unfrozen ground situated within, beneath, or between layers of permafrost.

Coriolis Effect

The apparent deflection of moving air or water masses resulting from Earth's rotation, causing moving fluids to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Ekman Transport

The net horizontal transport of surface water driven by the combined action of wind friction and the Coriolis force, pushing water toward the interior of ocean gyres.

Pycnocline

The ocean layer characterized by a rapid increase in water density with depth, separating the lower-density mixed surface layer from the high-density deep ocean layer.

Thermocline

A subsurface layer of the ocean or lake where temperature decreases rapidly with increasing depth, separating warm surface waters from colder, deeper layers.

Upwelling

The upward vertical movement of deep, cold, and nutrient-rich seawater toward the surface, commonly triggered along coastlines by surface water divergence.

Downwelling

The sinking of surface water into the deep ocean caused by surface water convergence, carrying oxygen-rich waters into deeper zones.

Thermohaline Circulation

Deep ocean density-driven circulation sustained by global differences in water temperature ('thermo') and salinity ('haline'), wherein cold, saline surface waters sink at the poles.

Atlantic Meridional Overturning Circulation (AMOC)

The major system of ocean currents in the Atlantic that transports warm surface waters northward and returns cold, dense deep waters southward.

Younger Dryas Cold Event

An abrupt climate cooling event (ca. $12.9\text{--}11.6\text{ ka}$) during the deglacial transition, marked by temperature declines of $10^\bot\circ\text{C}$ to $14^\bot\circ\text{C}$ in Greenland caused by the weakening or shutdown of the AMOC.

Dryas octopetala

An arctic-alpine flowering tundra plant whose widespread appearance in European fossil assemblages serves as the bio-indicator and namesake for the Younger Dryas cold event.

Lake Agassiz

A colossal Pleistocene proglacial lake in North America whose catastrophic freshwater discharge into the North Atlantic disrupted normal overturning circulation and initiated the Younger Dryas.

Paleoecology

The scientific discipline that investigates past ecosystems, biomes, and environmental conditions through ecological forensics such as fossil pollen, macrofossils, charcoal, ancient DNA, and sedimentary proxies.

No-Analog Community

A past biological assemblage composed of plant or animal species that have no modern counterparts living together under current climatic and geographic conditions.

Overkill Hypothesis

The theory proposing that the abrupt end-Pleistocene extinction of North American megafauna (such as mammoths and mastodons) was primarily driven by human hunting.

Hydrosphere

The total mass of water found on, under, and over the surface of a planet across liquid, solid (ice), and gas (vapor) forms.

Freshwater

Naturally occurring water containing a low concentration of dissolved salts and solids, having a lower density than ocean water and a freezing point of $0^\bot\circ\text{C}$.

Saltwater

Water found in oceans and seas containing a high concentration of dissolved salts, possessing a higher density than freshwater and a depressed freezing point of $-2^\bot\circ\text{C}$.

Estuary

A semi-enclosed coastal body of water where freshwater draining from rivers and streams mixes with saline ocean water.

Lacustrine Body

An enclosed, non-flowing inland freshwater body, consisting of lakes and ponds.

Fluvial Body

A flowing surface freshwater system, consisting of rivers, streams, and creeks.

Spring

A natural source point where groundwater under hydrostatic pressure or gravity discharges directly onto the Earth's surface.

Wetland

A land ecosystem where the soil is permanently or seasonally saturated with water, characterized by hydric vegetation with little to no open standing water.

Aquifer

An underground layer of permeable rock, sand, or gravel that stores and allows the flow of groundwater.

Evaporation

The thermodynamic process in which liquid water changes into gaseous water vapor in the atmosphere.

Transpiration

The biological process whereby plants release absorbed water vapor from their leaves into the atmosphere.

Sublimation

The phase change by which ice or snow transitions directly into atmospheric water vapor without passing through an intermediate liquid phase.

Deposition

The phase change by which atmospheric water vapor transitions directly into solid ice crystals without passing through the liquid phase.

Infiltration

The physical process by which surface water soaks through the Earth's surface into the upper soil layer.

Percolation

The downward movement of water passing through soil and rock layers beyond the root zone into the saturated groundwater table.

Runoff

The overland movement of unabsorbed precipitation or meltwater across the land surface via streams, rivers, and glacial flow into larger water bodies.