Chapter 6-9 Exam Flashcards
(122 cards)
1
Q
Three states of water:
A
solid (ice), liquid (liquid water), and gas (water vapor)
2
Q
the most prevalent state on Earth.
A
Liquid water
3
Q
The ___ shape of the ____ molecule causes it to be ____, acting like a ____ magnet. This characteristic leads to many unique properties including _______.
A
The angular shape of the water molecule causes it to be polar, acting like a weak magnet. This characteristic leads to many unique properties including the ability of water to dissolve many salts.
4
Q
In a _____, the atoms of oxygen and hydrogen share the energy of paired electrons
A
Covalent bond
5
Q
When a hydrogen atom in one water molecule is attracted to the oxygen atom of an adjacent water molecule, a _____ forms.
A
hydrogen bond
6
Q
A _____ bond is much stronger than a ____ bond.
A
covalent, hydrogen
7
Q
Water molecules in ice are held together by ______ in a rigid matrix in which the _________. Density of ice at 0oC is 0.917 g/cm3 (i. e., ice floats in water).
A
Water molecules in ice are held together by hydrogen bonds in a rigid matrix in which the molecules are farther apart than in liquid water, causing ice to be less dense than liquid water. Density of ice at 0oC is 0.917 g/cm3 (i. e., ice floats in water).
8
Q
______ is a powerful solvent. It dissolves more substances in greater quantities than any other common liquid due to the polar nature of the water molecule, which is caused by its angular shape.
A
Water is a powerful solvent. It dissolves more substances in greater quantities than any other common liquid due to the polar nature of the water molecule, which is caused by its angular shape.
9
Q
To evaporate water into water vapor, all _____ have to be broken, requiring much ______ input (540 calories per gram).
A
To evaporate water into water vapor, all hydrogen bonds have to be broken, requiring much energy input (540 calories per gram).
10
Q
Freezing temperature of pure water is ____ and boiling temperature of pure water is ____
A
Freezing temperature of pure water is 0 oC and boiling temperature of pure water is 100 oC.
11
Q
_____ and _____ points are unexpectedly high compared with molecules of similar molecular structure.
A
Boiling and melting points are unexpectedly high compared with molecules of similar molecular structure.
12
Q
Pure water has a density maximum at ____, and typical sea water has a density maximum at ____ (freezing temperature of sea water).
A
Pure water has a density maximum at 3.98oC, and typical sea water has a density maximum at -2oC (freezing temperature of sea water).
13
Q
Adding ____ to water decreases the freezing point, much like antifreeze keeps your radiator water from freezing.
A
Adding salt to water decreases the freezing point, much like antifreeze keeps your radiator water from freezing.
14
Q
1 cm3 of pure freshwater weighs ___ gram at 4 oC, the temperature of _____ density.
A
1 cm3 of pure freshwater weighs 1 gram at 4 oC, the temperature of maximum density.
15
Q
The heat capacity is the heat required to raise the temperature of 1 gram of a substance by 1 oC. The ocean is slow to heat up and slow to cool down due to its high heat capacity. Land is heated (or cooled) much quicker than the ocean. Thus, the local ocean has a moderating effect on local climate.
A
16
Q
For water, the latent heat of evaporation or vaporization is larger (540 calories per gram) than the latent heat of melting (80 calories per gram). It takes a total of 100 calories to raise the temperature of 1gram of freshwater from 0 to 100 oC.
Know how to figure total calories needed to change 1 gram of ice at 0 oC to water and then to water vapor. (See figures discussed in lecture).
A
17
Q
The thermocline is a layer in which a rapid vertical temperature change occurs. Halocline is a layer in which a rapid vertical salinity change occurs. Pycnocline is a layer in which a rapid vertical density change occurs. Lightest (most buoyant) water is above pycnocline.
A
17
Q
The thermocline is a layer in which a rapid vertical temperature change occurs. Halocline is a layer in which a rapid vertical salinity change occurs. Pycnocline is a layer in which a rapid vertical density change occurs. Lightest (most buoyant) water is above pycnocline.
A
18
Q
The ocean is density stratified. It can be divided into three layers: (1) surface zone, (2) thermocline/ pycnocline, (3) deep zone. The surface zone is in contact with the atmosphere and is usually well-mixed due to the action of wind and waves. The deep zone is separated from the surface zone by the thermocline except in the high latitudes where water temperature is fairly constant surface to bottom! Although, recent rapid melting of ice in polar regions is changing that! The bulk of the global ocean water (~90%) is found in the deep zone and has a relatively narrow range for its temperature and salinity.
A
19
Q
Away from continental margins in deep water, the thermocline extends from about 100m to 1000m. In deep water the thermocline controls the pycnocline. In continental shelf areas where river discharge is prevalent, the pycnocline may be more controlled by the halocline.
A
20
Q
How is water density affected by temperature and salinity?
A
When temperature decreases, density increases. When salinity increases, density increases.
21
Q
Sea surface salinity distribution: Near the equator due to prevalent rainfall, precipitation exceeds evaporation causing salinity to be relatively low. Near the mouths of large rivers, salinity is low. In the large high pressure systems (30 degrees N & S), precipitation is low relative to evaporation, resulting in high salinity. In the polar regions, salinity tends to be low in summer mainly due to the melting of sea ice.
A
22
Q
If evaporation exceeds precipitation, salinity increases. If sea ice forms, the salinity of the surrounding water increases initially, but salinity decreases when the denser salinity-laden water sinks. Salt is left behind both when water freezes and water evaporates.
A
23
Q
What are the major physical processes that control evaporation?
(Hint: What is wind speed and humidity gradients between surface and air at 10 meters)
A
24
The latent heat that is transferred with water vapor during evaporation is released
during condensation of water vapor into droplets/rain, which intensifies tropical cyclones!
25
What is a maritime and continental climate?
26
Water is very dense compared to air. At the Earth’s surface, human’s experience ~ 1 atmosphere of pressure. As one moves down in the water column, pressure increases rapidly. Every 10 m increase in water depth, causes a pressure increase of 1 atmosphere (1 kg/cm2 increase in pressure or 14.22 lbs/in2 ).
26
Water is very dense compared to air. At the Earth’s surface, human’s experience ~ 1 atmosphere of pressure. As one moves down in the water column, pressure increases rapidly. Every 10 m increase in water depth, causes a pressure increase of 1 atmosphere (1 kg/cm2 increase in pressure or 14.22 lbs/in2 ).
27
Seawater (and freshwater) absorbs incoming visible light, as it is transmitted downwards. Water is especially effective at absorbing red wavelengths, the longer end of the spectrum, which is absorbed in the top few meters of the sea surface. Clear open ocean waters have maximum transparency in the blue region, which means it is transmitted to deeper depths.
28
What is a secchi disk (dates back to 1800s) and what is it used for?
29
Less than 1 % of the light (all wavelengths) penetrates down to 100 meter depth in the clearest ocean waters. Photosynthesis takes place in this zone which is called the euphotic zone.
30
Refraction changes the direction of light and sound wave propagation in the ocean, when the waves move through or into an area of different density. Sea water is very transparent to sound. Underwater sound speed (~ 1500 m/s) depends on temperature and pressure. The SOFAR (Sound fixing and ranging) channel is a channel of minimum sound velocity at about 1000 meters deep. Sound is trapped in the SOFAR channel because when it tries to escape it is refracted back into it. Sound can propagate over long distances in the SOFAR channel. Thus, it is a very effective region for communication of marine animals for long distance. If sound travels towards a local maximum in sound speed, it refracts away from the zone and a shadow zone is created and submarines can hide out there!
31
* The six most abundant (by weight) ions in sea salts are; Chloride (Cl-), Sodium (Na+), Sulfate (SO4--), Magnesium (Mg++), Calcium (Ca++), and Potassium (K+). Which two make Epsom Salt? Which salt is most abundant?
32
* Salinity refers to the total amount of dissolved solids or salts in ocean water.
33
* Salinity of a typical sea water is close to 35 parts per thousand (35 g of salts in 1 kg of seawater).
34
* Weathering of rocks on land and outgassing through volcanoes and near mid-ocean ridges are the sources of the ocean’s salts.
35
What is advection? What is diffusion?
36
*Although salinity might vary in different parts of the ocean, the ratio of major salts or solids in seawater in the ocean is constant. This is referred to as the Principle of constant proportions or Forchammer’s principle.
37
* Salinity used to be determined by measuring chlorinity, total amount of chloride ions. In the digital age, it can be more conveniently determined by measuring electrical conductivity of seawater. Units of ‘ppt’ are used for chlorinity measurements and ‘psu’ for conductivity measurements. The latter means “practical salinity units”. Sometimes the units are omitted since it is a ratio.
38
* Residence time is the average length of time an atom spends in the ocean. Residence time of all the major salts are estimated to be very long. Residence time of gases and nutrients are much shorter as they are used in biological processes.
39
Photosynthesis in sea water increases concentrations of O2 and decreases concentrations of CO2, while respiration increases concentrations of CO2 and decreases concentrations of O2 . Below photic zone, oxygen decreases because photosynthesis is not occurring and due to uptake by animals and bacteria during decomposition of organic material.
40
What is a neutral pH? Is lower than neutral pH referred to as acidic or alkaline (also called basic)?
41
pH is a measure of ________. One unit of pH is a change in H+ ions of _________.
42
* Sea water is normally mildly alkaline (about pH 8), because of the carbon dioxide dissolved in it and the 3 main reactions that take place. At normal pH for seawater, bicarbonate ions are most prevalent. When pH drops (when carbon dioxide added), reactions tend to favor dissolving CaCO3 (shells or organisms, corals) and when pH rises, precipitation of CaCO3 is favored. Study the graphic that shows these reactions!
43
Dissolved inorganic carbon (from carbon dioxide) enhances the ocean’s buffering capacity, usually preventing broad swings of pH when acids or bases are introduced.
44
Dissolved inorganic carbon (from carbon dioxide) enhances the ocean’s buffering capacity, usually preventing broad swings of pH when acids or bases are introduced.
45
The ocean is a large sink for which gas, thus very involved in understanding the “global warming”?
46
The ocean is a large sink for which gas, thus very involved in understanding the “global warming”?
47
Ocean acidification has been documented by recent measurements. Continuation of this trend could lead to large-scale dissolving of skeletons of coral reef animals and pteropods, a component of plankton and food source for fish. Why is pH changing more rapidly in polar regions?
48
* Cold water holds more gas than warm water meaning that polar water is a good source of oxygen for deep water when it sinks.
49
The documented mean pH change in high latitudes since the Industrial Revolution is as much as 0.1, from 8.2 to 8.1. This change would make the ocean more acidic (really less alkaline) by 26% ! (See relationship between pH, H+ ions and acidity).
50
The documented mean pH change in high latitudes since the Industrial Revolution is as much as 0.1, from 8.2 to 8.1. This change would make the ocean more acidic (really less alkaline) by 26% ! (See relationship between pH, H+ ions and acidity).
51
The longest record of carbon dioxide measurements is from Mauna Loa observatory, Hawaii. How has carbon dioxide concentration changed since 1960? How does this compare to estimated levels dating back to 800,000 years?
52
Uneven heating of Earth from solar radiation causes circulation in the atmosphere and wind systems. Uneven heating occurs on many time and space scales. Factors include:
1)angle of sun’s rays hitting earth, 2) seasonal changes of this angle due to motion of Earth around sun and Earth's
axis tilt; 3) distribution of land/water and 4) Ice reflects almost all of the light that hits it, whereas
water absorbs most light.
53
ïWater vapor is a gas and humid air is lighter than dry air! This encourages vertical motion in tropics, especially within ITCZ (INTERTROPICAL CONVERGENZE ZONE).
54
ïWhat is the major way that heat and water vapor is lost from surface ocean? Evaporation (latent heat)
55
* Weathering of rocks on land and outgassing through volcanoes and near mid-ocean ridges are the sources of the ocean’s salts.
56
ïDriving forces for evaporation are wind speed and the gradient of water vapor between sea surface and 10m above sea surface. Thus, as sea surface temperature increases so does this gradient and evaporation.
56
ïWhat happens to salinity of ocean water when water evaporates, or the ocean water freezes?
57
Approximately 1/3 of the heat redistribution from tropics to poles occurs in the ocean and 2/3 in the atmosphere (as latent heat in water vapor). Therefore, poles don’t freeze solid!
58
Coriolis Effect: Occurs because of conservation of angular momentum on the rotating earth. This effect arises since we describe motions in the atmosphere and ocean relative to a fixed coordinate system but the coordinate system that we should be using for the earth is one that rotates. And Coriolis force varies from zero at equator to maximum value at poles.
58
Looking into the direction of movement, the Coriolis force acts to the right in the northern hemisphere, and to the left in the southern hemisphere. Thus, currents move to the right of the winds that force them, as one example.
59
*There are three atmospheric circulation cells in each hemisphere due to Coriolis force. These are the Hadley cell, Ferrel cell, and Polar cell. The lower surface branch of Hadley cell gives rise to the northeasterly (southeasterly) trade wind in the northern (southern) hemisphere. ITCZ (Inter Tropical Convergence Zone) is located where the NE trade winds, and SE trade winds meet (converge). The ITCZ moves seasonally following the warmest SST (which follows the sun). Within the ITCZ, surface air is heated by the warm ocean, leading to rising warm and moist air (low pressure results) and then more air from areas surrounding the low pressure converge to replace the rising air. Once the rising air reaches a high altitude, water vapor condenses, forming clouds and rainfall. ITCZ is characterized by clouds and rainfall. Winds can be light or stormy. Westerlies prevail within the Ferrel cell, and polar easterlies prevail within the polar cell. The boundary between the Ferrel cell and Polar cell is the polar front separating the cold polar air mass from the warmer air masses at mid-latitudes.
60
* Wind circulates counterclockwise around a low pressure system in the northern hemisphere. Wind circulates clockwise around a high pressure system in the northern hemisphere. Within low and high pressure systems the wind is geostrophic when the pressure gradient balances the Coriolis force.
61
Trade winds (0-30º N and 0-30º S) are characterized by steady and moderate surface easterly air flow (northeasterly winds in NH and southeasterly in SH).
62
Equatorial regions (~0º) are characterized by surface convergence, low pressure, usually light to no wind (called doldrums), copious cloud cover, high rainfall, and low salinity. They form at the convergence of the trade winds from Northern and Southern hemispheres. The ITCZ is located where the trade winds converge.
63
Subtropical high pressure systems (centered close to 30º N and 30º S latitude) are characterized by light wind, surface divergence, clear skies (few clouds), little rain and high salinity (excess of evaporation over precipitation (dry air maximizes evaporation).
64
Westerlies (30-60º N and 30-60º S) are characterized by prevalence of westerly air flow (southwesterly in NH) but often variable due to passage of high and low pressure systems.
65
* On a daily basis, large differences in heat capacities of land and ocean gives rise to sea breezes and land breezes. Seabreezes are best developed in the afternoon when land has been heated by the sun. Landbreezes are best developed at night after the land has cooled due to back radiation. They are driven by uneven heating of land and water. Baton Rouge is too far from the coast to experience seabreezes and landbreezes!
66
* Two types of strong storms: tropical cyclones (hurricanes, typhoons) which form over warm water ( > 26 oC). Tropical cyclones act to carry heat away from the tropics toward higher latitudes and contribute toward balancing the heat budget for the earth. Tropical cyclones obtain their energy from the ocean, via evaporation of water at sea surface as latent heat and release of energy to fuel the tropical cyclone upon condensation/precipitation of water within the storm.
67
Extratropical cyclones form at the polar front through the interaction of two air masses (cold and warmer). Cold fronts occur where the cold air mass collides with and intrudes underneath the warm air mass. They obtain their energy from temperature gradients. In the NH, these cyclones move equatorward and eastward. We call them cold front passages, cold air outbreaks, or winter storm systems. Typically, the winds rotate clockwise over time as the front approaches and then passes. Explosive cyclogenesis (decrease in pressure by 24 mb/day) occurs over the Gulf Stream regularly (esp in fall and winter season) when strong winds and
cold dry air flows over the warm Gulf Stream which increases the temperature and humidity gradient of the air mass and fuels intensification of the storm.
68
Surface divergence and upper level convergence are characteristics of high pressure systems
(air sinks).
69
Does air move from High pressure to Low pressure or Low pressure to High pressure?
70
Most deadly aspect of tropical cyclone at coast (wind or water)?
water
71
How does wind force change in relationship to wind speed changes?
Hint: if wind speed doubles, what happens to wind force?
A double of wind speed equals a quadrupling of wind force!
Wind force = wind speed 2
Pressure of system and wind speed correlates
72
When you fly in a jet from the U.S. west coast to the east coast, why is the trip usually quicker than flying in the reverse direction?
Development of an extratropical cyclone which derives most of its energy from temperature gradients along a frontal boundary (polar jet stream region)
Frontal systems generated at Polar Front move towards Southeast or South
Jet Streams form at high levels at cell junctions
73
What two factors together contribute to storm surge?
Hint: What causes the dome of water that travels under the hurricane in deep water?
- Low pressure-induced dome
- Winds driving dome onto coast
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Where do they form?
water > 26 C (80 F), Most often in tropical regions
75
What conditions are necessary for their formation?
- Sea surface temperature of > 26 C or > 80 F
- Deep oceanic warm surface layer above the thermocline, meaning large upper ocean heat content
- They only develop in an area of low surface pressure
- Minimal vertical shear of horizontal winds; winds are easterly throughout troposphere (10-15 km above sea surface)
- Low level rotation of winds
Coriolis force operational, therefore not withing a few degrees of Equator
Easterly Waves off African coast
76
Which ocean areas or currents are areas of high heat content in the Gulf of Mexico?
(unsure)
- High sea level in Loop Current indicates a deep later (of warm water that Hurricane interacts with (~100 m)
- Loop current intruded far north and west
77
Where are winds highest…in eye or within the eyewall?
eyewall, zero in eye
78
How many categories of hurricanes are available in the Saffir Simpson Scale?
5
79
Which side of the hurricane is the most dangerous looking in the direction of hurricane motion?
eyewall, right front
80
If an El Nino Warm Event is prevalent in the Eastern Pacific Ocean, how are NW Atlantic hurricanes affected?
- El Nino Cycle is 3-7 years (Interannual): El Nino reduces N Atlantic hurricane activity because the subtropical jet stream is strong, bringing upper level westerly winds, creating wind shear which weakens N ATLANTIC hurricanes.
- Result: N. Atlantic and East Pacific hurricane activity are out of phase (one is active while other is not)
81
There are two types of circulation in the ocean: (1) wind-driven surface circulation and (2) thermohaline circulation. Wind blowing at the sea surface directly drives circulation in the upper layer of the ocean (~top 1000m, strongest currents in surface mixed layer). Thermohaline circulation controls circulation below the thermocline/pycnocline and is driven by the density of water, i. e., by the temperature and salinity of the water mass. Water mass characteristics are generally formed at the sea surface by evaporation/precipitation and ice forming/melting.
81
Ekman transport moves near-surface water to the right (45 degrees) of the wind direction in the Northern Hemisphere, it moves water to the left of the wind direction in the Southern Hemisphere. In the Ekman layer, wind stress acting on the water particles is balanced by the Coriolis Force.
82
The Ekman effect changes with depth, as current directions rotate clockwise (to right in NH), and current speeds decrease with depth (called Ekman spiral) and rotate right in the NH. Average surface flow is about 45 degrees to right of wind. Average flow within Ekman layer (surface mixed layer to about 400 m)
83
Away from rivers and eddies, wind-driven currents (such as coastal currents) can be estimated as 3% of the wind speed. This is important to know for search and rescue operations!
84
Coastal Upwelling and Downwelling: Winds blowing along a coast cause either upwelling or downwelling depending on the wind direction relative to the orientation of the coast. In the NH, looking in the direction the wind blows towards (or with wind hitting your back), if the land is located to your left, the resulting Ekman transport moves the near-surface water away from the coast, causing upwelling of water along the coast from deeper depths. Coastal upwelling brings colder, deeper, and nutrient-rich water closer to the surface where sufficient sunlight is available, thus bringing about higher biological productivity. Local situation: Along the Louisiana coast, easterly winds (from the east) cause surface water movement towards the coast, coastal water level rises, downwelling occurs at the coast, and bottom water flows offshore. In the opposite case of westerly winds (from the west), surface waters move away from the coast, coastal water level falls, and bottom waters move upwards at the coast to replace the surface water (upwelling). Upwelling doesn't occur easily in areas where the continental shelf is wide, such as LA.
Along the Texas coast, the shelf is very narrow and coastal upwelling occurs regularly in summer when a southeasterly or southerly wind blows persistently and with strength. In many areas, where upwelling is persistent (Eastern Boundary currents) satellite SST imagery can be used to monitor cold water that upwells.
85
Subtropical gyres: Subtropical high pressure systems are in mid-latitudes (centered near 30ºN and 30º S). The northern half of this subtropical high pressure system in NH has westerly winds, while the southern half of this system has easterly winds. Ekman transport resulting from this wind pattern causes surface convergence in ocean. In fact, the center of this converging water in the North Atlantic produces sea level about 1 meter higher compared to surrounding waters of the North Atlantic Ocean. The resulting geostrophic current called the OCEAN GYRE flows clockwise in the northern hemisphere.
86
Each ocean gyre (5 altogether on Earth) has a Western and Eastern Boundary Current flanking the west and east sides of the gyre. Other currents, flowing west to east (at mid-latitudes in NH) and east to west (in tropics of NH) make the gyre continuous. In the North Atlantic, these are the North Atlantic Current and the North Equatorial Current.
87
The volume transport of currents is measured in Sverdrups. One Sverdrup = 1 million cubic meters of water per second. The Loop Current volume transport is 26 Sv on average. That volume is about 7 Superdomes per second. The Gulf Stream volume transport is about 55 Sv.
88
Western boundary currents (Gulf Stream, Brazil, Agulhas, Kuroshio, East Australian) are the strongest currents in the ocean. Speeds of 2-4 nautical miles/hour equivalent to 1-2 meters/second are common. They form where tropical waters pile up along a coast on the western side of an ocean basin (such as along the Yucatan coast, Mexico), forming a relatively narrow, deep, swift flowing current. Western boundary currents always flow away from the tropics towards higher latitudes. They are warm and deep currents (to 1000m), relatively narrow compared with Eastern Boundary currents, and lacking in nutrients (water is oligotrophic i.e., “biological deserts”).
89
Eastern boundary currents (e. g., Canary, Benguela, West Australian, California Current, Peru) are cool, broad, and relatively weak compared with Western boundary currents. The subtropical ocean gyres are displaced to the west because the magnitude of Coriolis force increases with latitude (zero at the equator and increasing with distance from the equator). Learn all the major currents in the North Atlantic Gyre and Western and Eastern Boundary Currents in South Atlantic (see powerpoint lecture file). Eastern Boundary currents have copious nutrients due to upwelling of deeper water, and they support big commercial fisheries (a lot of small to medium size fish such as menhaden, sardines).
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Antarctic Circumpolar Current (ACC): A steady unimpeded wind blowing from west to east around the Antarctic Continent drives the ACC which has the largest transport of any current.
91
Eddies in the Ocean: The ocean is full of eddies! Oceanic eddies (called “rings” near
Gulf Stream) are the oceanic counterpart of weather systems in the atmosphere (high and low pressure systems). Oceanic warm core eddies rotate clockwise in the NH, and are characterized by high sea surface height, and downwelling in their centers (warm cores). Ocean cold core eddies rotate counter-clockwise in the NH, have low sea surface height, and upwelling of colder water in their centers (cold cores). Until 1970's, oceanographers used to consider the ocean currents to be steady and stable. Satellite data were needed to reveal eddies and their rapid motions.
92
The Gulf Stream separates warm water in the Sargasso Sea to the southeast from the cold water to the Labrador Current. Often the Gulf Stream becomes unstable and develops meanders, and subsequently forms rings (or eddies). Rings northwest of the Gulf Stream are called warm core rings (because they contain warm water from the Sargasso Sea) and those southeast of the Gulf Stream are called cold core rings (because they contain cold water coming from north of the Gulf Stream). Eddies play an important role in mixing different water masses (they also mix chemical and biological materials) and transfer heat away from the tropics. The Gulf Stream volume transport is about 55 Sv, about twice that of the Loop Current. The Yucatan Current, Loop Current and Florida Current are basically the same current just passing through different geographic regions. Large warm core eddies in the Gulf of Mexico separate about once per year on average. They move west within the Gulf of Mexico and die in the “eddy graveyard” along the continental margin of Texas.
93
The Gulf Stream separates warm water in the Sargasso Sea to the southeast from the cold water to the Labrador Current. Often the Gulf Stream becomes unstable and develops meanders, and subsequently forms rings (or eddies). Rings northwest of the Gulf Stream are called warm core rings (because they contain warm water from the Sargasso Sea) and those southeast of the Gulf Stream are called cold core rings (because they contain cold water coming from north of the Gulf Stream). Eddies play an important role in mixing different water masses (they also mix chemical and biological materials) and transfer heat away from the tropics. The Gulf Stream volume transport is about 55 Sv, about twice that of the Loop Current. The Yucatan Current, Loop Current and Florida Current are basically the same current just passing through different geographic regions. Large warm core eddies in the Gulf of Mexico separate about once per year on average. They move west within the Gulf of Mexico and die in the “eddy graveyard” along the continental margin of Texas.
94
The Gulf of Mexico is full of eddies. Warm-core eddies are usually larger (250-400 km diameter), live longer (up to 1 year!), and extend deep so that they are vast reservoirs of heat to the atmosphere (intensifying hurricanes that encounter them). The centers of cold-core eddies (cyclones) are regions of upwelling with cool temperatures and high nutrients compared with surrounding waters at a similar depth. Cold-core eddies are regions of upwelling, more nutrients, more marine life! The Loop Current, warm and cold core eddies extend down to about 1000m in the water column. Below 1000m is a very different circulation system.
95
The Gulf of Mexico is full of eddies. Warm-core eddies are usually larger (250-400 km diameter), live longer (up to 1 year!), and extend deep so that they are vast reservoirs of heat to the atmosphere (intensifying hurricanes that encounter them). The centers of cold-core eddies (cyclones) are regions of upwelling with cool temperatures and high nutrients compared with surrounding waters at a similar depth. Cold-core eddies are regions of upwelling, more nutrients, more marine life! The Loop Current, warm and cold core eddies extend down to about 1000m in the water column. Below 1000m is a very different circulation system.
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(1) Eulerian measurements(from fixed location; platforms/moorings)
(2) Lagrangian measurements (from moving instruments, such as satellite-tracked drifters with drogue at depth of desired measurement)
What is an ADCP and which category is it used in?
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(1) CTD- Conductivity and Temperature with Depth – used from ship
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Gulf of Mexico circulation strongest currents are at the surface (top 100m). Minimum currents are found at about 1000m. Strongest currents are in the Loop Current, typically 2-4 nautical miles/hour or 1-2 m/s (one to two large strides per second)!
99
The ENSO is one of earth's mechanisms for redistributing excess heat from tropics to higher latitudes.
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The ENSO is one of earth's mechanisms for redistributing excess heat from tropics to higher latitudes.
101
"El Nino," which literally means "the little boy" in Spanish, refers to the Christ Child, and has been used by Peruvian fishermen since the l9th century to describe the appearance of warm water in the coastal region of Peru and Ecuador around Christmas. This was a regular annual event. However, in some years (at intervals of 2-7 years), the accumulation of anomalously warm water becomes excessive, often leading to disastrous results for the anchovy fishery in Peru. Soon, those anomalous years with excessive warming became known as "El Nino" years. During El Nino events, sea surface temperature along the South American coast could rise by 1 to 5 oC higher than normal. Thus, El Nino has come to mean a "warm event" in the equatorial Eastern Pacific Ocean area. The events usually start when the trade winds in the South Pacific (associated with the South Pacific High pressure system) weaken or collapse. This results in warm water flowing eastward to the coast of South America usually carried in a Kelvin wave. The strongest El Nino event in the last 150 years, occurred in 1997/98. The 1998 winter in California was marked by stormy conditions, floods, mudslides, etc., while Louisiana experienced the wettest January of this century. There are "cold events" also known as "La Nina" events (meaning the little girl) when the eastern Pacific is very cold, the western Pacific is very warm, and the trade wind is very strong.
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Early studies had viewed El Nino as primarily an oceanic event important only to the west coast of South America. More recent studies contributed toward linking El Nino to the atmospheric phenomenon known as the Southern Oscillation (SO), briefly described as a "massive seesaw" of atmospheric pressure between the eastern (Tahiti) and western South Pacific (Darwin).
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The Southern Oscillation was first noted by Sir Gilbert Walker in his studies on the Indian monsoon in the 1920s. He observed that when low air pressure is located in the western Pacific, high air pressure tends to occur in the eastern Pacific; and when high pressure is located in the western Pacific, low pressure tends to occur in the eastern Pacific. He termed this phenomenon the "Southern Oscillation" (because this phenomenon tends to be centered in the southern hemisphere).
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The Southern Oscillation is measured using sea level pressure difference between Tahiti and Darwin (Tahiti pressure – Darwin pressure). If negative, El Nino is occurring. If positive, La Nina is occurring. If zero, the conditions are average.
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Under "average" or “normal” atmospheric conditions, the western Pacific is characterized by warm sea surface temperature, low air pressure, and cloudy and rainy climate, while the eastern Pacific is characterized by low sea surface temperature, high air pressure, and dry climate.
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A better understanding of the dynamics of ENSO focuses on how the ocean responds to fluctuations in trade winds. Under "normal" easterly trade wind conditions over the Pacific, the trade winds pile up warm water in the western Pacific. Consequently, sea surface temperature in the eastern Pacific tends to be cooler. If the trade winds are stronger than normal, water is abnormally cold in the eastern Pacific. La Nina conditions are an extreme of the normal condition.
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On the other hand, a typical ENSO warm event (El Nino) is characterized by weakening trade winds in the SE Pacific Ocean. This results in the "sloshing back" of warm water accumulated in the western Pacific towards the eastern Pacific. This sloshing back of warm water takes a few months to reach the South American coast. It should be noted that “sloshing back” of warm water toward the South American coast occurs near the equator.
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On the other hand, a typical ENSO warm event (El Nino) is characterized by weakening trade winds in the SE Pacific Ocean. This results in the "sloshing back" of warm water accumulated in the western Pacific towards the eastern Pacific. This sloshing back of warm water takes a few months to reach the South American coast. It should be noted that “sloshing back” of warm water toward the South American coast occurs near the equator.
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"Sloshing back" is initiated by a weakening of the trade winds. As the warm water sloshes back toward the South American coast, the atmospheric convection zone, that used to be located in the western Pacific, will migrate eastward as well, following the eastward movement of the warm water pool. Consequently, the zone of rainfall will accompany this eastward migration of the convection zone. As this zone of convection and rainfall passes the central Pacific Ocean, those tropical paradise islands, such as Tahiti, that are usually known for "good weather all year around," will be subjected to stormy and rainy conditions. When this convection and rainfall zone arrives at the South American coast, the eastern Pacific and the neighboring South American countries will experience heavy rainfall (even the desert regions of Peru and Ecuador often experience flooding).
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"Sloshing back" is initiated by a weakening of the trade winds. As the warm water sloshes back toward the South American coast, the atmospheric convection zone, that used to be located in the western Pacific, will migrate eastward as well, following the eastward movement of the warm water pool. Consequently, the zone of rainfall will accompany this eastward migration of the convection zone. As this zone of convection and rainfall passes the central Pacific Ocean, those tropical paradise islands, such as Tahiti, that are usually known for "good weather all year around," will be subjected to stormy and rainy conditions. When this convection and rainfall zone arrives at the South American coast, the eastern Pacific and the neighboring South American countries will experience heavy rainfall (even the desert regions of Peru and Ecuador often experience flooding).
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When the warm water reaches the eastern Pacific, many conditions are reversed between the western Pacific and the eastern Pacific. Sea surface temperature is now warmer than normal in the eastern Pacific and colder than normal in the western Pacific. A large atmospheric convection (and rainfall) is now located in the eastern Pacific, and the air is descending in the western Pacific (causing drought) Consequently, air pressure is low in the eastern Pacific, and high in the western Pacific. Winds may blow from west to east (opposite to the normal direction of trade winds). A zone of rainfall is located in the eastern Pacific while the western Pacific experiences dry conditions ("drought"). Now, we can understand why El Nino and the Southern Oscillation are closely coupled.
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When the warm water reaches the eastern Pacific, many conditions are reversed between the western Pacific and the eastern Pacific. Sea surface temperature is now warmer than normal in the eastern Pacific and colder than normal in the western Pacific. A large atmospheric convection (and rainfall) is now located in the eastern Pacific, and the air is descending in the western Pacific (causing drought) Consequently, air pressure is low in the eastern Pacific, and high in the western Pacific. Winds may blow from west to east (opposite to the normal direction of trade winds). A zone of rainfall is located in the eastern Pacific while the western Pacific experiences dry conditions ("drought"). Now, we can understand why El Nino and the Southern Oscillation are closely coupled.
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Upon reaching the South American coast, some portion of the warm water propagates poleward along the North and South American coasts. In fact, during the 1982/83 El Nino (one of the three strongest El Nino events of the 20th century), the warm water propagated all the way to Alaska, carrying many tropical fish species with it. As the reflected warm water spreads out in the tropical Pacific, the storm formation region expands. Consequently, places usually associated with good weather, such as the eastern Pacific off Mexico and Hawaiian Islands, are hit more frequently by strong hurricanes during El Nino.
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Upon reaching the South American coast, some portion of the warm water propagates poleward along the North and South American coasts. In fact, during the 1982/83 El Nino (one of the three strongest El Nino events of the 20th century), the warm water propagated all the way to Alaska, carrying many tropical fish species with it. As the reflected warm water spreads out in the tropical Pacific, the storm formation region expands. Consequently, places usually associated with good weather, such as the eastern Pacific off Mexico and Hawaiian Islands, are hit more frequently by strong hurricanes during El Nino.
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Warm water migration throughout the Pacific Ocean during the life cycle of El Nino will disrupt the global weather pattern, simply due to the massive amount of warm water involved in the process and the major changes in atmospheric convection that results. The west coast of the U. S. usually experiences stormy conditions. The western states of the U. S. experience floods, snowmelts, and mudslides. Marine and bird life in South America, coral reefs across the Pacific all suffer from this climatic anomaly. During an El Nino event, the subtropical Jet Stream in the atmosphere over the East Pacific Ocean strengthens as the water warms. During El Nino, the Jet Stream often splits into two branches with the southern branch (known as a Subtropical Jet Stream) often making a large southward excursion. Consequently, winter storms coming from the Pacific Ocean follow this southern branch Jet Stream and bring more precipitation into California, the southwestern and southeastern U. S. El Nino reduces hurricane formation in the NW Atlantic Ocean, Caribbean Sea and the Gulf of Mexico as winds at upper levels in the atmosphere prevail from the west, which is not conducive to hurricane formation (called wind shear).
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_____ and _____ measurements are being made by the ____ straddling the equatorial Pacific Ocean. The data allow for _____ and also provide _______
Ocean and atmosphere measurements are being made by the TAO array straddling the equatorial Pacific Ocean. The data allow for monitoring rapidly changing conditions in real time and also provide critical data used to improve the prediction of the initiation and evolution of ENSO events.
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ITCZ is Intertropical Convergence Zone!
