Oceanography Exam #2

129-156, 163-179, 187-192, 197-229, Ch. 5-7

deep-ocean currents

below the pycnocline, 90% of all ocean water, slow velocity

seawater density increases →?

dec temp, inc salinity

\

El Nino

* Walker Cell Circulation disrupted


* High pressure in eastern Pacific weakens
* Weaker trade winds
* Warm pool migrates eastward
* Thermocline deeper in eastern Pacific
* Downwelling
* Lower biological productivity → Peruvian fishing suffers

la nina

* Increased pressure difference across equatorial Pacific
* Stronger trade winds
* Stronger upwelling in eastern Pacific
* Shallower thermocline
* Cooler than normal seawater
* Higher biological productivity

el nino warm phase occurs every __ years

2-10

occurence of enso events

highly irregular

phases usually last 12-18 months

Thermohaline circulation

deep ocean circulation driven by temperature and salinity caused density differences in water

\
originates in high latitude surface ocean

cooled, now dense surface water sinks and changes little

sources of deep water

antarctic bottom water, north atlantic deep water,

antarctic bottom water

* Densest water in the open ocean
* Rapid freezing produces cold, high density water
* Spreads into all ocean basins

north atlantic deep water

* Cools, sea ice forms, water sinks
* North Atlantic in the Norwegian Sea
* Labrador Sea
* Dense salty Mediterranean Sea
* Less Dense than Antarctic Bottom Water

subtropical convergence

downwelling

doesn’t produce deep water

antarctic and arctic convergence

downwelling

antarctic intermediate water

oceanic common water

pacific and indian oceans

* don’t have a source of NHDW
* north pacific water = low salinity
* indian ocean = too warm

AABW and NADW mix to form OCW → lines bottom of Pacific and Indian

T-S Diagram

temp and salinity

lines of equal density

study

converging surface water - downwelling

* Surface waters move toward each other
* Water piles up
* Low biological productivity

coastal upwelling

* Ekman transport moves surface seawater offshore.
* Cool, nutrient-rich deep water comes up to replace displaced surface waters.
* Western U.S. and cool San Francisco temperatures

coastal downwelling

* Ekman transport moves surface seawater toward shore.
* Water piles up, moves downward in water column
* Lack of marine life

other coastal upwelling causes

* Offshore winds
* Seafloor obstruction
* Coastal geometry change
* Lack of pycnocline → High latitude oceans

walker circulation cell

normal conditions

* Air pressure across equatorial Pacific is higher in eastern Pacific
* Strong southeast trade winds
* Pacific warm pool on western side of ocean
* Thermocline deeper on western side
* Upwelling off the coast of Peru

Discuss how the dipolar nature of a water molecule makes it such an effective solvent of ionic compounds.

The dipolar characteristic of water is really the key component to why water is such an effective solvent of ionic compounds. This is because the water molecules reduce the attraction between opposing ions, allowing the water molecules to stick to polar chemical compounds. This reduced attraction between the opposing ions allows for ionic compounds to separate easily.

Why are the freezing and boiling points of water higher than would be expected for a compound of its molecular makeup?

The freezing and boiling points of water are much higher than expected because the water molecule is made up of hydrogen bonds and van der Waals forces, which are really hard to break. These bonds require additional heat energy to overcome, and therefore leave the freezing and boiling points of water much higher than similar chemical compounds.

Describe how excess heat energy absorbed by Earth’s low latitude regions is transferred to heat deficient higher latitudes through a process that uses water’s latent heat of evaporation.

Water has a high specific heat, so when evaporation happens at the low latitude regions, a large amount of heat energy is absorbed. These vaporized molecules(from the evaporation) then travel to the heat deficient higher latitude regions through an atmospheric convection cell. Once the vaporized molecules reach the higher latitude region, they are condensed due to the decreased temperatures in these areas. The heat energy that was absorbed is released due to the condensation, which carries the excess heat energy from low latitude regions to the high latitude regions.

What physical conditions create brackish water in the Baltic Sea and hypersaline water in the Red Sea?

In the Baltic Sea, the physical conditions that create brackish water are freshwater and seawater. The freshwater from rivers or high rainfall mix with the seawater and create a ‘diluted’ salinity, or somewhat salty mix. In areas like the Red Sea, the physical conditions that create hypersaline water are high evaporation rates and limited open-ocean circulation. This causes excessive salt water, and occurs often in seas and inland bodies of water.

Describe three processes by which dissolved components are added to seawater and four processes by which dissolved components are removed from seawater.

Three processes where dissolved components are added to seawater are stream runoff or river discharge, volcanic eruptions, and hydrothermal activity at the mid-ocean ridge. Runoff transports dissolved components directly into the seawater and a large part of these components accumulate over time. Volcanic eruptions can add dissolved components into seawater by dispersing sulfur and other compounds through ashes and wind. Lastly, hydrothermal activity at the mid-ocean ridge can both add and remove dissolved components in seawater. Four processes where dissolved components are removed from seawater are absorption and precipitation, sea spray, biological processes and hydrothermal activity at the mid-ocean ridge. Precipitation and absorption remove dissolved components through the water cycle process. Sea spray releases small particles of dissolved compounds into the atmosphere, usually after a wave break. Lastly, biological processes like the production of hard parts by marine organisms also removes dissolved compounds from seawater.

Describe the halocline, including where it occurs in the ocean.

A halocline is a layer of rapidly changing salinity with depth. It goes from about 300 to 1,000 meters below the surface. In the low-latitude curve, the salinity decreases, while in the high-latitude curve, the salinity increases.

Using the processes that affect seawater salinity, explain why there is such a large range of salinity variation at the surface but such a narrow range of salinity at depth.

There is a large range of salinity variation at the surface compared to the depths because of all of the salinity-altering processes that occur at the surface rather than the depths. Processes like precipitation, formation of sea ice, evaporation, runoff, and sea ice melting have no effects on the deeper water, compared to the surface water.

Describe the pycnocline, including where it occurs in the ocean.

A pycnocline is a layer of rapidly changing density. It goes from about 300 meters to 1,000 meters below the surface, like how the halocline does.

If there is a net annual heat loss at high latitudes and a net annual heat gain at low latitudes, why does the temperature difference between these regions not increase?

The temperature difference doesn’t increase because atmospheric winds and ocean currents transfer heat from low latitudes to high latitudes. The heat gained and heat lost evens eachother out.

The Coriolis effect causes moving objects to curve to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Describe the underlying cause of the Coriolis Effect.

The underlying cause of the Coriolis Effect is the difference in speed of the Earth’s rotation at different latitudes. The object itself isn’t moving along a curve,but rather a straight path. Because of Earth’s rotation, however, the object seems to move along a curved path, i.e. the Coriolis Effect

Discuss the patterns and trends that you notice when looking at the global wind belts and boundaries shown in Figure 6.12 and Table 6.2

The most distinct pattern I see is that the northern hemisphere and the southern hemisphere are essentially mirrored images. The air masses, pressure, andwinds seem to be oscillating every 30 degrees or so.

Name the major wind belts in each hemisphere and identify the boundaries between these wind belts

The major wind belts in each hemisphere are the NE and SE trade winds, the prevailing westerlies, and the polar easterlies. Between the NE and SE trade winds is the Doldrums boundary. Around the 30 degree latitudes/ between the SE trade winds and the Prevailing Westerlies and between the NE trade winds and the Prevailing Westerlies are the Horse latitudes boundaries. The Polar Front boundaries are located between the Polar Easterlies and the Prevailing Westerlies of both hemispheres, so around 60 degrees. Lastly, the Polar high pressure boundaries are located at 90 degrees, between the Polar Easterlies.

Describe the difference between a sea breeze and a land breeze. What causes them to form? When do they occur?

a.) A sea breeze is when the rising air creates a low-pressure region over the land,pulling the cooler air over the ocean toward land during the afternoon

b.) A land breeze is when the land surface cools (at night) and creates a high-pressure region that causes the wind to blow from land

Describe the difference between sea ice, icebergs, and shelf ice, including how each is formed.

Sea ice is basically just frozen seawater. It starts out as small crystals that buildup creating a slush. This slush begins to form into a thin sheet, while wind stress and wave action breaks it down into what is called pancake ice, which eventually then forms into ice floes, or layers of ice. Icebergs are found at sea, but originate by breaking off from glaciers on land. They are formed by vast ice sheets onland. These sheets grow from snow pile-up and form outward towards the sea.Once the ice sheet reaches the sea, it either breaks and produces the iceberg

that way, or it floats on top of the water and breaks up from currents, wind, orwaves. Lastly, shelf ice is a thick floating sheet of ice that is formed at the edge of glaciers and breaks off to produce vast plate-like icebergs

How many subtropical gyres exist worldwide? List each subtropical gyre and then list the main currents that exist within each subtropical gyre.

1. There are five subtropical gyres worldwide. 


1. North Atlantic Subtropical Gyre


1. Currents: North Atlantic Current, Canary Current, North Equatorial Current, Gulf Stream
2. South Pacific Gyre


1. Currents: South Equatorial Current, East Australian Current, West Wind Drift, Peru Current
3. North Pacific Subtropical Gyre


1. Currents: North Pacific Current, California Current, North Equatorial Current, Kuroshio Current
4. South Atlantic Subtropical Gyre


1. Currents: South Equatorial Current, Brazil Current, West Wind Drift, Benguela Current
5. Indian Ocean Subtropical Gyre


1. Currents: South Equatorial Current, Agulhas Current, West Wind Drift, West Australian Current

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

The subtropical gyres in the Northern Hemisphere move in a clockwise direction because of the anticyclonic flow of the high-pressure air cells. Same occurs for the subpolar gyres but instead the air cells are low-pressure and move in a cyclonic flow.

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

Upwelling areas are associated with an abundance of marine life because the upwellings bring high concentrations of nutrients. These nutrients allow for marine life to thrive, and an increase in productivity.

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

1. During the Northeast Monsoon, there is rapidly cooling air which causes high atmospheric pressure. This high pressure causes dry air, which means little precipitation. The winds during this season flow from Southwest Asia off the land and over onto the ocean. These offshore winds cause the North Equatorial Current to flow from east to west, and the Somali Current flows south along Africa’s coast. The equatorial countercurrent is also established.
2. During the Southwest Monsoon, there is low atmospheric pressure which influences the heavy precipitation on land during this season. The winds reverse, blowing from the ocean onto the land. During this season, the North Equatorial Current gets replaced by the Southwest Monsoon Current, flowing in the opposite direction. The Somali Current also reverses and flows northward.

Describe the changes in atmospheric and oceanographic phenomena that occur during El Nino/La Nina events including changes in: atmospheric pressure, wind direction and intensity, walker circulation, weather, equatorial surface currents, coastal upwelling/downwelling, abundance of marine life, sea surface temperature, the pacific warm pool, sea surface elevation, and the position of the thermocline

1. El Nino


1. Atmospheric pressure


1. Reduced pressure along the coast of South America
2. Wind direction and intensity


1. Southeast trade winds diminish
2. When El Nino is really strong, the trade winds will blow in the opposite direction
3. Walker circulation


1. Reduced difference between the high and low pressure regions


1. Between the southeastern Pacific high-pressure cell and the Indonesian low-pressure cell is weakened
4. Weather


1. Difficult to predict
2. More storms
5. Equatorial surface currents


1. Current strengthens
6. Coastal upwelling/downwelling


1. No more upwelling
2. Downwelling can occur when the warm water is being pushed against the western coast of South America
7. Abundance of marine life


1. Decrease in productivity and marine life abundance
8. Sea surface temperature


1. Increase in sea surface temperature in Eastern Pacific waters
9. The Pacific Warm Pool


1. Equatorial water isn’t being pushed into the warm water near Indonesia, so instead it gets pushed eastward along the equator


1. Can reach the coasts of North and South america
10. Sea surface elevation


1. Usually rises
11. The position of the thermocline


1. Thermocline boundary between warm surface water and cool depth water flattens
2. La Nina


1. Atmospheric pressure


1. Larger pressure difference across the Pacific ocean
2. Wind direction and intensity


1. Strengthened trade winds
3. Walker circulation


1. Strengthens
4. Weather


1. Difficult to predict
5. Equatorial surface currents


1. Weakens?
6. Coastal upwelling/downwelling


1. Increased upwelling
7. Abundance of marine life


1. Increased nutrients → increased productivity → increased marine life
8. Sea surface temperature


1. Cooler than normal across the equatorial South Pacific
9. The Pacific Warm Pool


1. Shrinks to the west
10. Sea surface elevation


1. Sea levels drop
11. The position of the thermocline


1. Shallows out in the Eastern pacific

Discuss the origin of thermohaline vertical circulation. Why do deep currents form only at high latitudes?

These thermohaline vertical circulations start up in high latitude surface oceans and they happen when the cooler, denser surface water sinks. The salinity of this water increases with the formation of sea ice. The reason deep currents form only at high latitudes is because they are driven by the differences in density and temperatures, and the low-latitude water is too warm and never dense enough to sink I think.

Antarctic Intermediate Water can be identified throughout much of the South Atlantic based on its temperature, salinity, and dissolved oxygen content. Why is it colder and less salty - and why does it contain more oxygen - than the surface water mass above it and the North Atlantic Deep Water below it?

This water is colder because of the formation at the Antarctic Convergence. It is less salty because the water that is being sunk is at a higher latitude. There is more oxygen in this water because it’s colder water than that of the North Atlantic Deep Water and the surface water mass.

Geometry of Water

hydrogen atoms separated by 105°

covalent bonds

Water polarity and what gives it this polarity?

dipole

the geometry

Hydrogen bonds contribute to..

Cohesion

High surface tension

Water’s thermal properties

Water’s density

How is water the universal solvent?

Water molecules stick to other polar chemical compounds, which reduces attraction between ions of opposite charges

\
Electrostatic attraction between oppositely charged ions

* Reduced by water
* Causes Na+ and Cl to separate
* hydration

water has ___ melting and boiling points because why?

high

additional heat energy needed to overcome hydrogen bonds and van der Waals forces

Heat Capacity

amount of heat required to raise the temperature of 1 gram of a substance 1°C

Water has a ___ heat capacity because why

high

can take in or lose heat without changing temperature

specific heat

– heat capacity per unit mass

latent heat

hidden heat

water has ___ latent heat

high

when water undergoes a change of state, what happens to the heat?

large amounts of heat absorbed or released

latent heat of melting

E needed to break intermolecular bonds that hold water molecules in place in ice crystals

latent heat of vaporization

* E added at boiling point to break intermolecular bonds
* Change state from liquid to vapor
* Break all hydrogen bonds

Latent heat of evaporation

Evaporation: conversion of liquid to gas below the boiling point

Latent Heat of Condensation

Water vapor cools, condenses, releases heat to surrounding air

Latent Heat of Freezing

Heat released when water freezes

precipitation and evaporation latitudes

Global thermostatic marine effect

Oceans moderate temperature changes from day to night and during different seasons

Global thermostatic continental effect

Land areas have greater range of temperatures from day to night and during different seasons

Global thermostatic effects

Water density

* Generally the density of water increases as temperature decreases
* From 4°C to 0°C the density of water increases.
* Unique property of water
* Ice is less dense than liquid water.
* Changes in molecular packing
* Water expands \~9% in volume as it freezes

Density

Increased pressure or adding dissolves substances ____ the max density temp

decreases

Dissolved solids also reduce the ____-

freezing point of water

\
most seawater never freezes

Salinity

Total amount of solid material dissolved in water

Includes dissolved gases, Excludes organic substances

Typical Ocean water salinity

35 parts per thousand

How is salinity found and how is it expressed

Ratio of mass of dissolved substances to mass of water sample

Expressed in ppt (parts per thousand) ‰

Components on salinity in water

Chloride, sodium, sulfate, magnesium, calcium, potassium, other

Is salinity constant?

no

Hypersaline

evaporation dominated

Brackish

Influx of fresh water from runoff, precipitation

What causes differences in salinity?

Seasonal variations → flux of freshwater, dry/humid

What processes decrease salinity?

runoff, melting sea ice, melting icebergs and precipitation

What processes increase salinity?

sea ice formation, evaporation

Comparison of major dissolved components in streams with those in seawater

Residence time

Average length of time a substance remains dissolved in seawater

Ions with long residence times are ____

in high concentrations in seawater

• (Na+ 260 million year)

Ions with short residence times are ___

in low concentration in seawater

Steady-state

Average amount of element of interest remains constant

\
Oceans haven’t increased in salinity over time (rate at which an element is added = rate at which it is removed)

Why has open ocean maintained a constant composition?

rapid mixing relative to long residence times

Ions with long residence times __ and those with short __

accumulate; removed

Conservative constituents of seawater occur in __ proportions because they have a __

constant; long RT

Conservative constituent examples

Na, K, Mg, Ca, Cl, sulfate, borate

nonconservative constituents have a __ residence time and are associated with _ cycles

short; seasonal, biological or short geological

nonconservative constituents examples

dissolved nitrate and phosphate

RT of seawater constituents

High latitudes are associated with __ salinity

low

equatorial region is associated with __ salinity

low

mid latitudes are associated with __ salinity

high

salinity and temp vs latitudes

halocline

layer of rapidly changing salinity with depth

\~300-1000 meters below surface

\
* the deep ocean is relatively constant

pH scale

Ocean pH

slightly alkaline - surface water avg. is 8.1

ocean water pH dec with depth

pH, depth, and CCD

Freshwater density

1\.000 g/cm3

ocean surface water density

1\.022 to 1.030 g/cm3

density differences impacts

creates deep-ocean currents, ocean mixing