Chapter 7 OCE

How may subtropical gyres exist worldwide?

5 subtropical gyres worldwide

Explain why ocean currents have the potential to generate even more power than wind farms, which are much more common today.

Currents move more slowly than wind, but have more energy because water has 800 times the density of air giving the ocean enough power to support the entire globe without adding pollution to the air. Also, because currents flow day and night while the wind and sun are limited to seasons, weather conditions and daylight hours

How many main currents exist within each subtropical gyre?

Each subtropical gyre is composed of 4 main currents flow progressively into one another.

Explain why Gulf Stream eddies that develop northeast of the Gulf Stream rotate clockwise and have warm-water cores, whereas those that develop to the southwest rotate counterclockwise and have cold-water cores.

Meanders along the north boundary of the Gulf Stream pinch off and trap warm Sargasso Sea water in eddies rotating clockwise creating warm-water core rings. The warm rings contain shallow, bowl-shaped masses of warm water. They remove large volumes of water as they disconnect from the Gulf Stream. Cold nearshore water spins off to the south of the Gulf Stream counterclockwise-rotating cold-core rings. They may exceed 310 miles in diameter and over 2.2 miles deep

Discuss the origin of thermohaline vertical circulation. Why do deep currents form only in high-latitude regions?

Origin of Thermohaline vertical circulation: Deep-ocean circulation or thermohaline circulation begins at the surface of high-latitude where cold temps are consistent. Density is increased with the cold temp and salinity High latitudes maintain cold temps, the sea ice forms due to more salinity both creating conditions for pycnocline (rapidly changing levels of density).

Describe the Different ways in which currents are measured? PART C: Indirectly

Pressure gradients: Slopes of ocean surfaces (Downhill) water flow to determine internal density & pressure across an area of ocean. Radar altimeters: Launched aboard earth observing satellites to determine lumps in ocean surface caused by underlying sea floor. Doppler Flow Meter: low frequency sound send signals through water to measure sound waves to determine current movement

1. Describe differences between sea ice, icebergs, and shelf ice, including how each is formed.

Sea Ice: Forms directly from seawater beginning like a needle-like, hexagonal crystal which becomes numerous and partially frozen creating slush. Slush forms a thin sheet broken by wind stress and wave action into disk-shaped pieces called pancake ice. The pancakes merge together to form larger ice floes which merge & create large sheets that produce pressure ridges. Process: Pancake ice, Ice floes and Pressure ridges Icebergs: A body of floating ice that has broken away from a glacier. Formed by vast ice sheets on land created by accumulation of snow & slowly flow out to sea. As sea, it either breaks up or produces icebergs. Two main iceberg-producing regions are Greenland and Antarctica Shelf Ice: In Antarctica, edge of glaciers form thick floating sheets of ice called shelf ice which break off and produce extensive plate-like icebergs.

Why does the formation of sea ice tend to be a self-perpetuating process?

Sea ice forms at the surface, leaving only a small percentage of dissolved components to be accommodates into the crystalline structure of ice. This results in most of the dissolved substances remaining in the surrounding water, causing salinity to rise. Increasing the number of dissolved materials decreases the freezing point of water, but also increasing salinity of water increases its density and its tendency to sink. As it sinks, it is replaced by lower-salinity & lower-density water from below which freezes more readily than high-salinity water. This creates a circulation pattern that enhances formation of sea ice!

On a base map of the world, plot and label the major currents involved in the surface circulation gyres of the oceans. Use colors to represent warm versus cool currents and indicate which currents are western intensified. On an overlay, superimpose the major wind belts of the world on the gyres and describe the relationship between wind belts and currents.

See print out

Describe the global effects of severe El Niños

Severe El Ninos influence worldwide weather patterns by altering the atmospheric jet stream and producing unusual weather throughout the globe, either wetter or drier, warmer or cooler than normal.

Describe changes in atmospheric and oceanographic phenomena that occur during El Niño/La Niña events, including changes in atmospheric pressure, winds, Walker Circulation, weather, equatorial surface currents, coastal upwelling/downwelling and the abundance of marine life, sea surface temperature and the Pacific Warm Pool, sea surface elevation, and position of the thermocline

WALKER CIRCULATION is the resulting atmospheric circulation cell in the equatorial South Pacific Ocean. NORMAL: Walker Circulation creates precipitation more prevalent in the Pacific in Indonesia, New Guinea & Northern Australia, strong southeast trade winds are due to pressure differences, Pacific Warm Pool causing Thermocline to form at a upward curve near South America resulting in Upwelling bringing up colder water near the shore. EL NINO: no walker circulation, low-pressure increases precipitation is in abundance on the South American continent and dry, drought conditions to Indonesia and Northern Australia, trade winds in reverse cause the Pacific Warm Pool to spread across Pacific sending much warmer water into areas that harm Marine Iguanas of Galapagos Islands and coral reefs leaving them in ruins like Tahiti & Galopagos changing the thermocline into a more solid line allowing for no upwelling which brings cold water to the surface. This change in current with much warmer water also kills anchovies which diminish marine life and devastate fishing industries in areas like Peru by making the water temp up to 18 degrees higher than normal. The warm water heads to the west coast of the Americas, increasing average sea level & number of tropical hurricanes formed in eastern Pacific. LA NINA: The "cool phase" of El Nino is La Nina and occurs typically after a period of El Nino. This produces more normal conditions but intensified due to large pressures difference across Pacific Ocean. This creates stronger Walker Circulation, stronger trade winds, causes more upwelling, a shallower thermocline in eastern Pacific so a band of cooler than normal water stretches across the equatorial South Pacific.

What is one of the first indications that an El Niño event may be occurring?

Warm water originating near Australia migrates toward South America.

In relation to ocean circulation, a gyre is __________.

a large, circular-moving loop of surface water

Compare the forces that are directly responsible for creating horizontal and deep vertical circulation in the oceans. 2) What is the ultimate source of energy that drives both circulation systems

1- Surface currents occur when wind driven currents move water horizontally & remain on surface. Density driven circulation moves vertically (Mixes deep masses of ocean water) 2. MAJOR WIND BELTS of the world affect the pattern of ocean surface currents.

Ekman transport is an average path of motion that, under ideal conditions, is at ________ to the wind's direction.

90 degrees

What are the two major deep-water masses? (2) Where do they form at the ocean's surface?

ANTARCTIC BOTTOM WATER NORTH ATLANTIC DEEP WATER (2) ANTARCTIC BOTTOM WATER comes from southern subpolar latitudes beneath sea ice along the margins of the Antarctic continents. Rapid winter freezing produces very cold, high-density water that sinks down the continental slope of Antarctica. NORTH ATLANTIC DEEP WATER comes from northern subpolar latitudes in the Norwegian Sea. Deep water flows as a subsurface current into the North Atlantic. It also comes from the margins of the Irminger Sea off southeaster Greenland, Labrador Sea, and the dense, salty Mediterranean Sea

Discuss the advantages and disadvantages of building an offshore current power system.

Disadvantages include the expense to build the systems, they are difficult to maintain, potentially hazardous to ship traffic, and moving devices in the ocean could potentially disturb, injure or kill marine life. challenges with moving parts exposed to seawater for long periods of time experience corrosion and biofouling, and variability of current flow causes irregular power generation. Advantages include that sea floor devices could act as makeshift marine protected areas because fishing practices would not occur at these locations, currents carry 800 times the density of air and offer far more energy, avoid polluting the air, currents are constantly flowing day and night,

Diagram and discuss how Ekman transport produces the "hill" of water within subtropical gyres that causes geostrophic current flow. As a starting place on the diagram, use the wind belts (the trade winds and the prevailing westerlies). What causes the apex of the geostrophic "hills" to be offset to the west of the center of the ocean gyre systems?

Ekman transport deflects surface water to the right in the Northern Hemisphere, so a clockwise rotation develops within an ocean basin and produces the SUBTROPICAL CONVERGENCE of water in the middle of the gyre, causing water within all subtropical gyres to pile up in the center of the subtropical gyre, there is a hill of water within all subtropical gyres as much as 6.6 feet high.

How often do El Niño events occur? Using Figure 7.24, determine how many years since 1950 have been El Niño years. Has the pattern of El Niño events occurred at regular intervals?

El Nino occurs about every 2-10 years Since 1950, there have been 26 years that indicate El Nino conditions The pattern of the 50's, 60's & early 70's was consistent but less frequent, increasing over the decades between 1975 to current 2020.

Draw and describe several different oceanographic conditions that produce upwelling.

Equatorial upwelling occurs due to diverging surface water. Coastal upwelling is due to coast winds and the effects of Ekman transport. Offshore winds, sea floor obstructions, or a sharp bend in a coastline. High-latitude regions where there is no pycnocline.

Describe western intensification, including the characteristics of western and eastern boundary currents of subtropical gyres

Factors that cause western intensification include the Coriolis effect. Western boundary is faster, narrower, and deeper than the eastern boundary currents. The western boundary current transports larger volumes of water.

Describe the different ways in which currents are measured: PART B: Directly Measured currents

Floating device released into the current its position is tracked over time Current measuring device like Propeller Flow Meter: Released from fixed position (Pier or stationary ship)

Describe how the distribution of life in the ocean would be different if there were very little dissolved oxygen in deep-water currents.

If high-latitude surface waters did not sink and eventually return from the deep sea to the surface, there would be very little life in the deep ocean because there would be no oxygen for organisms to breathe. Also, life in surface waters might be significantly reduced without the upwelling of deep water that brings nutrients to the surface

Explain why no matter where you are in the ocean, if you go deep enough, you will encounter Oceanic Common Water.

It lines the bottoms of ocean basins whether they have deep-water mass or not. ( FACT)OCEANIC COMMON WATER is created when Antarctic Bottom Water and North Atlantic Deep Water mix.

Using Figure 7.29, notice that AAIW and NACSW fall on the same density line. What single measurement would allow you to tell them apart? Explain.

Temperature. The change in temperature is typically the greatest influence on density and will cause the water masses to behave differently more readily than the salinity shifts

1. How is La Niña different from El Niño? Describe the pattern of La Niña events in relation to El Niños since 1950 (see Figure 7.24).

The "cool phase" of El Nino is La Nina and occurs typically after a period of El Nino. This produces more normal conditions but intensified due to large pressures difference across Pacific Ocean. This creates stronger Walker Circulation, stronger trade winds, causes more upwelling, a shallower thermocline in eastern Pacific so a band of cooler than normal water stretches across the equatorial South Pacific

Explain why subtropical gyres in the Northern Hemisphere move in a clockwise fashion while Subpolar gyres rotate in a counterclockwise pattern.

The Coriolis Effect is why subtropical gyres in Northern Hemisphere move in clockwise fashion move to (Land). Coriolis effect deflects the currents away from the equator.

Explain why upwelling areas are associated with an abundance of marine life.

The cold water is rich in nutrients and creates an abundance of high PRODUCTIVITY containing microscopic algae and this establishes the basis of the food web which supports incredible numbers of larger marine life such as fish and whales.

1. Describe changes in atmospheric pressure, precipitation, winds, and ocean surface currents during the two monsoon seasons of the Indian Ocean.

Winter: air over Asian mainland rapidly cools, creates high atmospherics pressure which causes the wind to blow from southwest Asia off the continent and out over the ocean called Northeast Monsoon. Little precipitation due to the air associated with high pressure over land is dry Summer: winds reverse because of lower heat capacity of rocks and soil compared with water, the Asian mainland warms faster than the adjacent ocean, creating low atmospheric pressure over the continent. The winds blow strongly from the Indian Ocean onto the Asian landmass. There is heavy precipitation on land because the air brought in from the Indian Ocean is warm and full of moisture.

Western intensification is ________.

caused by the rotational center of a gyre being located to the west of the ocean basin's geographic center, thus causing more water to flow within a narrower "channel"

The California Current is a ________ current that flows ________.

cold; south

Describe the different ways in which currents are measured!!

measured: Directly & indirectly.

In subtropical gyres, western boundary currents have all of the following characteristics except being __________.

relatively wide

Surface ocean currents are caused by ___________, whereas deep currents are the result of __________.

surface wind belts; density differences

The ocean's deep water is initially formed at the _________ and in _________ regions.

surface; subpolar

The Gulf Stream is a ________ current that flows ________.

warm; north

The East Australian Current is a ________ current that flows ________.

warm; south