Chapter 9 Flashcards
ocean circulation
what are ocean currents
mass flow of water (the term is usually reserved for
horizontal movement)
what are surface currents
the horizontal flow of water at or near the ocean’s surface
what is a thermohaline current
water circulation produced by differences in
temperature and/or salinity (and therefore density)
deep ocean circulation driven by differences in water density. which impacts around 90% of the ocean water.
Surface ocean circulation is driven primarily by _______ and modified by ________.
wind; the Coriolis effect and land
What is the primary driver of shallow oceanic circulation?
wind
what is a gyre
circuit of mid-latitude currents around the periphery of an ocean basin.
Most oceanographers recognize five gyres plus the Antarctic Circumpolar
Current
what is most commonly believed to be a potential impact of global warming on thermohaline circulation?
Melting ice caps near Greenland would input fresh water into the system, reducing the density of surface water and preventing it from sinking, thus slowing down the oceanic conveyor belt.
The large-scale circular patterns of ocean surface currents found in each ocean are known as
gyres
what are boundary currents
North-to-south or south-to north ocean surface current whose properties are influenced by the presence of a coastline.
what are western boundary currents
currents that run along the western side of the ocean basin (i.e. the east coasts of the continents). Since these currents come from the equator, they are warm water currents, bringing warm water to the higher latitudes and distributing heat throughout the ocean. It transports warm waters towards the poles in both hemispheres. It has an increased velocity.
It is a narrower current. It is a deeper current.
what are westerlies
the dominant wind bands between 30 and 60 degrees latitude in each hemisphere
what are eastern boundary currents
These currents come from high latitude areas, so they deliver cold water to the lower latitudes. Together, these currents combine to create large-scale circular patterns of surface circulation called gyres. In the Northern Hemisphere the gyres rotate to the right (clockwise), while in the Southern Hemisphere the gyres rotate to the left (counterclockwise).
what are the 5 major gyres
the North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian
what is the north pacific gyre composed of
the North Equatorial Current on its southern boundary, which turns into the Kuroshio Current (a.k.a. the Japan Current) bringing warm water north towards Japan. The Kuroshio flows into the North Pacific Current which moves east towards North America, where it becomes the California Current to complete the gyre
what is the north Atlantic gyre composed of
North Equatorial Current flowing into the Gulf Stream along the east coast of the United States. The Gulf Stream merges into the North Atlantic Current to move water towards Europe, which then becomes the Canary Current as it moves south to join the North Equatorial Current.
what is the Antarctic Circumpolar Current (ACC)
the only current that connects all of the major ocean basins, and in terms of the amount of water that it transports, it is the largest surface current on Earth. creates the southern boundary for all of the Southern Hemisphere gyres. flows from west to east and is driven by westerlies
what is the south atlantic gyre composed of
the South Equatorial Current, the Brazil Current, the ACC, and the Benguela Current
what is the south pacific gyre composed of
the ACC becomes the Peru Current (also known as the Humboldt Current) moving up the west coast of South America, before joining the South Equatorial Current.
what is the indian gyre composed of
the ACC, the West Australia Current, the South Equatorial Current, and the Agulhas Current
what is a geostrophic gyre
A circular current around the periphery of an ocean basin in balance between the Coriolis effect and the pressure gradient
true or false: Thermohaline circulation generally creates faster currents than wind-driven surface circulation.
false
In the Pacific Ocean, the major currents flowing towards the equator are the:
California and Peru
true or false: In both hemispheres, western boundary currents transport warm water towards the poles
true
what is the gulf stream
the major surface current flowing northwards along the Atlantic coast of the U.S. and Canada
how is the gulf stream formed
from the convergence of the North Atlantic Equatorial Current bringing tropical water from the east, and the Florida Current that brings warm water from the Gulf of Mexico
what is western intensification
currents on the western side of a gyre are faster, deeper, and narrower than currents on the eastern side. The increase in speed of surface currents as they pass along the western boundary of an ocean basin. Due to coriolis effect
what is an eddy
Loop of swirling water, formed along the edge of a permanent current when two sides of a meander connect, trapping warm or cold water in its centre; it is still attached to the main current.
what are rings
Freestanding spinning mass of water that can be several hundreds of kilometres across and can exist for a few years; it can have a cold or warm centre.
what is a warm core ring
shallow, bowl-shaped water masses about 1 km deep, and about 100 km across, that rotate clockwise as they carry warm water in to the North Atlantic. Clockwise eddies
what are cold core rings
cone-shaped water masses extending down to over 3.5 km deep, and may be over 500 km wide at the surface. Counterclockwise eddies
what is ekman transport
Net water transport due to the Coriolis Effect in the upper 100 m of the ocean, which theoretical direction is 90° to the right of the wind direction in the Northern Hemisphere.
true or false: Ocean currents off of the east coast of a continent tend to be faster and stronger than those off of the west coast.
true
Gyre currents reflect the equilibrium point between gravity and Ekman transport known as __________ flow.
geostrophic
Spinning rings of water are formed on either side of the Gulf Stream:
when large meanders close and break away from the current
what is the ekman spiral
where each layer of water is deflected relative to the layer above it, forming a spiral that extends down to about 100 m
what is gyre rotation dependant on
the wind and the Coriolis Effect impacting the surface currents and movement below the surface due to Ekman transport
what are characteristics of the gulf stream
Narrow (50–100 km wide), Deep (to 1.5 km), Fast (average speed 6.4 km/h)
describe Geostrophic flow in the Northern Hemisphere
Ekman transport moves water into the middle of the gyre, where it “piles up.” Gravity causes the water to flow back “downhill.” Viewed from above, as the water in the center flows “downhill” the Coriolis force deflects the movement to the right causing the system to rotate clockwise
in terms of western intensification how are currents affected northern and southern hemisphere
currents on the western side of the gyres travel through a much narrower area than the currents on the eastern side. To move the same volume of water through each side, western boundary currents are faster, deeper, and narrower than eastern boundary currents. The center of rotation of the gyre is also closer to the western side of the gyre
what are characteristics of western gyre currents
volume is passing through a narrower area, so the current must travel faster in order to transport the same amount of water in the same amount of time
what are characteristics of eastern gyres
the current is much wider, so the flow is slower
Eddies are packets of water that:
may maintain their physical and chemical identity for weeks.
Eddies that pinch off of the Gulf Stream and move north are ______ core rings.
warm
what is upwelling
Circulation pattern in which deep, cold, usually nutrient-laden water moves toward the surface. provides nutrient rich water to marine producers. where surface currents are diverging, or moving away from each other leads to high productivity zones
what is downwelling
Circulation pattern in which surface water moves vertically downward. Occurs in areas of surface convergence. Leads to a deeper thermocline. leads to low productivity zones
what is El Nino
a periodic climatic situation in which warm water extends all or most of the way to the eastern edge of the equatorial Pacific
what is El Niño-Southern Oscillation (ENSO).
the fluctuating atmospheric conditions that lead to the localized ocean warming of El Niño
Under normal (i.e. non-ENSO) conditions what occurs?
strong trade winds, high pressure and dry conditions over Peru, colder water in the eastern Pacific, upwelling off Peru, low pressure and rain over Indonesia
El Niño events seem to be the result of:
weakening or reversal of the trade winds
Under El Niño conditions, what occurs?
high pressure and dry conditions over Indonesia, low pressure and rain over Peru, warmer water in the eastern Pacific, weak trade winds
what is the process of El Nino
El Niño: Climate event in the Pacific Ocean.
Normal Conditions: Winds push warm water westward.
El Niño Conditions: Weaker winds, warm water moves eastward.
Effects: Changes global weather, impacts rainfall, temperatures, and ecosystems.
what is La Nina
a periodic climatic situation in which colder than normal water extends throughout the equatorial Pacific
Under la nina conditions what occurs
the trade winds are unusually strong, leading to increased upwelling and transport of deep, cold water to the surface. opposite of an El Niño, bringing cooler and wetter conditions to the northwestern United States and Canada, while the southeastern US receives below-average precipitation
what is the difference betewen El Nino and La Nina
El Niño is warmer sea surface temperatures and disruptive weather patterns, while La Niña is cooler sea surface temperatures and its own set of distinct weather impacts.
What are some impacts of El Nino
–Widespread droughts in the Philippines and many South Pacific island nations.
–Severe coral bleaching on the Great Barrier Reef in Australia.
–One of the most destructive bushfire seasons in Australia, in part due to low rainfall.
–High rainfall in the southeastern United States
and parts of California, leading to flooding.
–Mild, low-precipitation winter in the New
England region of the United States.
–Severe flooding in Peru and Argentina.
–Droughts in many portions of southern Africa.
–Nearly 100 million people worldwide suffered a lack of food or water from flooding and droughts.
–Peru suspended its second anchovy fishing season due to low biomass, and an anticipated 20% reduction in the yearly catch.
what is Langmuir circulation
Shallow circulation of water in horizontal, spiral bands driven by strong winds.
what are characteristics of Langmuir circulation
it forms adjacent rotating cells but that rotate in opposite directions. It creates alternating divergence and convergence zones at the surface. creates corkscrew circulation patterns that are parallel to the wind
what is thermohaline circulation
deep ocean circulation driven by differences in water density
what is an undercurrent
A current flowing beneath a surface current, usually in the opposite direction.
what is a counter current
A surface current flowing in the opposite direction from an adjacent, dominant surface current.
what is a transverse current
East-to-west or west-to-east current linking the eastern and western boundary currents.
he major site of dense deep-water formation is in the _____ sea and becomes the_____
Weddell and Antarctic Bottom Water (AABW)
What creates the fastest currents?
Wind driven circulation
Geostrophic circulation within a gyre is driven by:
gravity
True or false :The speed of wind-driven currents decreases with increasing depth.
true
The densest water in the oceans is ___________ water.
Antarctic Bottom
The two major sites of bottom water formation are:
Weddell Sea and Greenland sea
what is a Contour current:
a bottom current made up of dense water that flows around
(rather than over) seabed projections, tends to follow flow parallel to depth
contours (=contour current)
what is a water mass
a volume of seawater with a distinctive density as a result of its unique profile of temperature and salinity
Describe the water mass Antarctic Bottom Water (AABW)
densest deep water mass is formed in the Weddell Sea of Antarctica, AABW sinks to the bottom in the Weddell Sea and then moves north along the bottom into the Atlantic, and eastthrough the Southern Ocean
Describe the water mass North Atlantic Deep Water (NADW)
NADW is sinking in the Greenland Sea. This is less dense than AABW and forms layer above the AABW as it flows across the equator to the south, As the NADW moves to the Antarctic continent, it is brought to surface, some NADW rises because upwelling process due to weak polar thermocline. when NADW reaches the surface, some travels south where it will contribute to the production of new AABW, NADW that moves north encounters the Antarctic convergence, making down welling. This sinking NADW becomes a new water mass; Antarctic Intermediate Water (AAIW)
describe water mass Antarctic Intermediate Water (AAIW)
sinks and creates a layer between the surface water and the NADW, surface water in equatorial Atlantic, also called the Central Atlantic Surface Water, is warm and low density, so it stays at surface and does not contribute much to thermohaline circulation.
describe the water mass Central Atlantic Surface Water
very warm and low density, therefore it remains at the surface and does not contribute much to thermohaline circulation
Describe the water mass Mediterranean Intermediate Water (MIW)
In Atlantic, flows through Straits of Gibraltar into open ocean, water is warm and salty from warm temperatures and high evaporation characteristic of the Mediterranean Sea, so it is denser than normal surface water and forms layer about 1-1.5 km deep. Eventually this water will move north to the Greenland Sea, where it will cool and sink, becoming the dense NADW.
what is Caballing
mixing of two water masses of identical densities but different
temperatures and salinities, such that the resulting mixture is denser than its
components
what are Isopycnals:
Isopycnals: lines of equal density
Describe T-S diagrams
provide a visual representation of the relationship between temperature and salinity in the ocean at different depths
These curves depict how temperature and salinity vary with depth, use their point of intersection to calculate the density of the water
what is the ocean conveyor belt
cycle of rising and sinking water transporting water between the surface and deep circulation, plays a crucial role in regulating Earth’s climate by redistributing heat and influencing weather patterns. may take about 1000-2000 years to complete
what is the importance of the ocean conveyor belt
Heat transport and temperature/climate
regulation, Brings oxygen to deeper
waters, Brings nutrients to surface
waters, Studying the history of the ocean conveyor belt provides valuable insights into past climate changes, plays a role in the global carbon cycle by transporting dissolved gases, affect sea level by redistributing water masses
What is he future for thermohaline circulation
Increased warming, particularly in the Arctic, could lead to continuing melting of the polar ice caps adding fresh water to polar surface, creates low density low salinity surface layers that cant sink disrupting conveyor belt preventing nutrient transport
