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Geoscience Midterm Review Questions
Terms in this set (33)
What are the thermocline, halocline, and pycnocline? Are they related to temperature, salinity and density of seawater? Are they the same in all places in the ocean?
Thermocline is the change in temperature and decreases as it goes deeper
• Halocline is salinity (saltyness) and it increases as you go lower
• Then you pycnocline is change in density and it increases as you go lower
• They all change at the same place
How is the ocean stratified by density? What physical factors are involved? What names are given to the ocean's density zones?
• Pycnocline is where density changes between 200 and 1000. And it increase the deeper you go
• Surface zone 2%
• Pycholine 18%
• Deep Zone 80%
Why does ice float?
• Ice floats because it is less dense than the water that it floats on
How do temperature and salinity influence the solubility of gas in seawater?
As temperature and salinity increases the solubility decreases.
What is Residence time of an element in seawater? How do you calculate resident time?
The time it takes an element to do a full water cycle. Amount of the element/input rate. The average time a element remains in solution in seawater. The amount of time its living with Ariel.
How does addition of salt to water change the freezing (boiling) point of water?
Salt ions strengthen the bonds, which helps them to keep better together so it takes more to break them
What is heat capacity? What is latent heat? Make sure to understand the diagrams we used in lecture #4. What's the difference between sensible heat and latent heat?
• Heat capacity is heat required to change the temperature of a given mass
• Latent heat is what energy it takes for water to change different forms. Changes the forms.
• Sensible heat rises the temperature.
How is heat different than temperature?
Heat is energy. Temperature is how hot something is.
Why is water a polar molecule? What properties of water derive from its polar nature?
Water is a polar molecule because it has an unequal charge distribution
• bonding of oxygen to hydrogen
• 105 degree angle
• creates surface tension
• bonds are constantly breaking and reforming
How is Ocean deep water different from shallow water?
• Density of water is higher the deeper you go
• its colder
• everything is more condesences
• salinity is still about 35
• photosynthesis is not possible
• more algeeeea
Surface water on Earth most likely came from where?
Why do we say there is one world ocean? Over time, does water from the Atlantic and Pacific Oceans mix with waters from the Baltic and Mediterranean seas?
This comes from the Deep Thermohaline Circulation
Which is greater - the average depth of the ocean, or the average elevation of the continents?
The average depth of the ocean is 4 times greater
What is the "Goldilocks Principle" as applied to Earth and the Oceans?
• Everything is just right for the earth
• Large enough for gravity to retain a gaseous atmosphere
• Distance from sun is in the life zone (water does not totally freeze or boil, letting us live
• There is a liquid outer core within earths interior it generates a protective magnetic field that shields the surface from harmful solar radiation
What are the main factors that influence plankton blooms?
Sunlight and nutrients are readily available to the plants. Water temperature, density, and salinity, hydrography of the region, availability of nutrients, what species and the amount of phytoplankton biomass that is present, what types of zooplankton are grazing on the phytoplankton, and available sunlight levels
Make sure that you understand the main aspects of the Coriolis effect
The primary factor affecting the amount of deflection resulting from the Coriolis effect is the length of time a particle is in motion. Thus, even at low latitudes, a large Coriolis deflection is possible if an object is in motion for a long time.
What are the connections between large scale wind patterns and the pattern of surface ocean circulation?
Frictional drag of the wind on surface waters imparts both a direction and a speed to surface waters. High wind speeds produce fast surface currents. Coriolis impacts the direction.
What is a gyre? What factors determine the large-scale pattern of surface ocean circulation in the N. Atlantic?
Due to the prevailing winds (trades between 0 and 30 degrees and westerlies between 30 and 60 degrees), the ocean basins located in either hemisphere tend to move in a circular pattern. The rotation direction is clockwise in NH and counter clockwise in SH. This type of general ocean circulation pattern is termed a GYRE. As the net water movement is towards the center of the gyre, water tends to PILE-UP near the center resulting in topographic features which can be measured by satellites
The factors that determine the surface ocean circulation in the N. Atlantic is the Gulf Stream, western boundary gyres, and wind.
Are there any differences between the flow of surface waters on the Eastern and Western side of ocean basins? If so, what are they?
One noteworthy aspect of gyre circulation is the tendency of western boundary currents to be intense. This results from the pile up of water along the western boundary of the ocean basin which forces the water to be focused along the western basin wall.
What are the similarities and differences between gyres and large scale ocean surface currents in the northern and southern hemispheres?
In the northern hemisphere, gyres move clockwise and in the southern hemisphere, they move counterclockwise. They both push the water eastward at the southwest in the northern hemisphere and the north west in the southern hemisphere
Large scale pattern of winds. What are the main cells? Why do they produce a regular pattern of low and high pressure at specific latitudes?
Hadley Cell - air rises at equator and downwells at about 30 deg. latitude as a warm, dry airmass, moving towards equator at surface
Polar Cell - sinking of cold, polar air with equator ward movement; meets mid-latitude air at "Polar front"; high pressure dominates in polar region.The winds are also deflected by the Coriolis "force"
Mid-Latitude Cell - polar movement of airmass, rising towards the "Polar front"; low and high pressure alternates along frontal zone.
The patterns of low and high pressure are due to the winds associated with them. The 0-30 degrees contains the trade wind belt (prevailing easterlies), the 30-60 the prevailing westerlies, and the polar easterlies at high latitudes. (The wind descriptions refer to which way the wind blows)
Why do the winds generally come from the east for locations from 30° S to 30° north?
The prevailing easterlies occur between 0-30 degrees because of the trade winds which blow to the east in the tropic zone.
What is the general pattern of heating on Earth, averaged over a year? Is it random or is there a systematic variation as a function of latitude?
More solar energy is absorbed in the tropics. Heat is then transferred to the higher latitudes until reaching the polar regions and then coming back down with cold air. The polar regions receives the warmer air masses the latest and are the coldest regions with the least solar energy absorption. This is the same in the surface waters as well stretching from the tropic region to the polar region.
What are the main factors that determine how heat is transported from low to high latitudes?
The oceanic heat transport via surface currents is driven by atmospheric circulation patterns. Wind Forcing of Surface Currents . Frictional drag of the wind on surface waters imparts both a direction and a speed to surface waters. High wind speeds produce fast surface currents. Coriolis impacts the direction. The latent heat transfer by evaporation from sea surface
Make sure that you understand the main aspects of the Ekman spiral
The Ekman spiral predicts that the net motion of surface water is 90 degrees to the right of the wind direction in the N. Hemisphere and 90 degrees to the left of the wind direction in the south pacific.
model assumes that a homogeneous water column is being set in motion by wind blowing across its surface. The Coriolis effect causes the resulting surface current to move at 45 degrees to the right of the wind in the Northern Hemisphere
In response to the Westerly and NE Trade winds, Ekman transport pushes water toward 30 deg. latitude and this water "piles up" at this latitude
Think about the connection between surface currents and deep water in the ocean. What makes water sink from the surface and become deep water? How does deep water circulation play a role in heat transfer and global ocean circulation?
Most of the deep water in the oceans today is formed in high latitudes where surface waters are cooled by heat exchange with overlying colder air. As the temperature drops, the density of sea water increases until it exceeds the density of water below. At this point the surface water will sink to great depths and begin its long travel around the ocean basins where it is upwelled to surface.
As previously discussed, the relative buoyancy of water masses involves both temperature and salinity differences. When surface water becomes denser than the underlying water mass, the surface water will sink, seeking a depth at which it will be stable in the density column
Think about how temperature and salinity and density vary with depth in the ocean. What do these curves look like, on average, in the tropics vs. the mid-latitudes, vs. polar regions.
Temperature decreases as the depth increases. Salinity increases as the depth increases. Density increases as depth increases. As the latitude increases, the change in temperature decreases from surface to deep parts.
What is the photic zone and why is it important? Do all wavelengths of light penetrate seawater in the same way?
The photic zone is the layer where photosynthesis can still occur because the waves of light still penetrate the water. This causes the water to have a light blue tint. Shorter wavelengths of visible light (e.g. blue) penetrate deeper than longer wavelengths (e.g. red). Note depth where light intensity is 1% of surface value-- somewhat greater than 100 meters for blue, about 100 m for green, much less for red.
Most biomass production occurs in upper 40% of photic zone where light intensity >20% of surface intensity
Why is photosynthesis important in the oceans? How does photosynthesis affect the concentration of dissolved gases in the oceans?
Photosynthesis occurs and creates oxygen in the water by absorbing the energy from the sun. Phytoplankton dwell in the photic zone in all parts of the ocean. The organic matter they produce is the source of energy for nearly all other ocean life
Note that photosynthesis (and formation of plant organic matter) requires sunlight and nutrients. Organic matter is consumed by animals and plants (respiration), supporting their growth. Nutrients must be "recycled" (excreted by animals, "regenerated" by bacteria) to be reused by plants
Decreases carbon dioxide and increases Oxygen
Why is mixing of deep waters up into surface waters important for life in the oceans?
The deep waters contain nutrient rich waters. When the water is brought up to the surface this brings the nutrients to the surface water and to the phytoplankton to bloom.
What role do bacteria play in the oceans? If there were no bacteria in the oceans, what effect would that have on the amount of carbon that got buried in sediments at the bottom of the ocean?
The bacteria take the organic matter and convert it into nutrients which is then recycled into the surface water and reused as nutrients for the phytoplankton and fish. The bacteria pick up the organic matter and transform them into nutrients instead in the aphotic zone instead of them just falling into the sediment and being "loss to sediment"
What are the major groups of phytoplankton?
diatoms, coccolithophorids, dinoflagellates
What are the main factors that influence seasonal variations in phytoplankton?
Seasonal changes in light (sun angle, hours of daylight). Seasonal changes in water-column stability (more stability, less nutrients mixed to surface). Predator/prey interactions (changes in "grazing" by zooplankton)
"Changes in latitude, changes in attitude"