Oceanography Prelim 1 + 2 Questions Verbatim

With regard to the global carbon cycle, how does the magnitude of CO 2 sequestered by the global ocean through photosynthesis and, separately, the magnitude of CO 2 released by the global ocean through respiration compare to the magnitude of CO 2 emitted by humans through fossil-fuel burning?

Ocean respiration and ocean photosynthesis are each much larger than human emissions.

Net Primary Production and Photosynthesis are equivalent terms.

False

Which light level produces zero Net Primary Production?

Compensation Light Level

Which type of phytoplankton has the growth advantage at low nutrient concentration?

Small cells

Which nutrient limits the growth of phytoplankton in the Southern Ocean?

Iron

Why is primary production in the Eastern Equatorial Pacific higher than in the Western Equatorial Pacific?

The thermocline is shallower in the Eastern Equatorial Pacific

Why do coastal upwelling regions experience seasonal increases in primary production?

Because the winds driving upwelling is seasonally variable.

Where is the critical depth located relative to the compensation depth?

Deeper

If phytoplankton mix a little bit below the compensation depth, then net primary production averaged over the course of a day will be negative.

False

Why should you thank the ocean for every other breath you take?

Because primary production in the ocean constitutes about half of global primary production.

Which region comprises most of the global ocean primary production

Open ocean

What do oceanographers mean when they say that pelagic ecosystems are strongly size structured?

They mean that body size is the dominant factor that determines what trophic level any given animal species will reside in.

What is the level of Exploitation Efficiency for the case of small grazers feeding on small phytoplankton in tropical regions?

Exploitation Efficiency is High

Given a Trophic Transfer Efficiency of 10%, how many units of fish would be produced each year if you started with 1000 units of phytoplankton?

phytoplankton > zooplankton > fish

10

Where is overall production of harvestable fish greatest?

Coastal Region

What do heterotrophic bacteria use for their source of energy and carbon?

Dissolved organic matter.

Prochlorococcus contributes to more than a quarter of the total global ocean primary production.

True

Where does the Biological Carbon Pump operate most efficiently?

In Eutrophic regions

What factor or factors determines where a given species resides in the rocky intertidal?

All of the above

What happens to the level of biodiversity in the rocky intertidal region when the starfish Pisaster is removed?

Biodiversity decreases

What is meant by the term Trophic Cascade?

It describes the alternating decrease-increase-decrease in the abundance of organisms in adjacent trophic levels.

What is responsible for the massive declines in kelp forests off the California coast over the past decade?

Sunflower starfish decline due to bacterial disease

What percentage of a coral’s nutrition comes from its Zooxanthellae symbionts?

60%-90%

What resource is in short supply in coral reefs and under stiff competition with other coral species?

Space

What happens when coral reefs are overfished?

It reduces herbivory on macro algae and allows the macro algae to overgrow and smother coral species.

How much coral cover has already been killed off over the past 150 years?

50%

What percentage of corals will be lost if global warming reaches 2 ºC?

>99%

What unique skeletal feature is used to connect all of the transitional fossils between Pakicetus and modern whales?

Ear Bone

What time of year should you visit Hawaii if you wanted to see humpback whales?

Winter

Which of the following noise sources did Professor Chris Clark (me included) express the most concern for impacting whale population success?

Commercial Shipping

Off-shore oil exploration uses air guns to blast noise that penetrates deep into ocean sediments in search of subsurface pools of oil. The magnitude of the air guns is on the order of dynamite exploding. How often do these air guns blast noise into the ocean?

Once every 10 seconds for several months

Whether or not whales can be humanely killed is one ethical issue when it comes to commercial whaling. What was the other ethical issue discussed in class?

Hunting species that are listed as vulnerable or endangered with extinction.

What property of water allows it to form hydrogen bonds with adjacent water molecules?

The polar charge distribution with one side of the molecule having a slightly positive charge and the other side having a slightly negative charge.

What two opposing molecular forces/energies determine the three phases of water (solid, liquid and gas)?

H-bonds and Thermal-Kinetic energy

When a given amount of heat energy is added to the surface ocean, the temperature does not rise nearly as much as it would if the same heat energy were added to land or atmosphere. Why is this the case?

Water has an exceptionally large specific heat capacity.

When water vapor is transported by the winds it is transporting heat energy stored as latent heat that will eventually be turned back into sensible heat when it condenses back to rain at a new location.

True

What determines surface ocean salinity for a given geographic location?

The difference between Evaporation and Precipitation in the region.

Where is surface ocean salinity lowest?

Subpolar North Pacific

What happens to the concentration of nitrate and phosphate in deep ocean waters (4000 meter) as the deep waters move from the North Atlantic to the North Pacific?

The concentration increases

Why is oxygen high in the upper layer of the ocean?

Both answers

What causes of an oxygen minimum zone to form just below the sunlit layer of the ocean?

A high level of microbial respiration, fueled by dead organic material raining down.

Why does the oxygen concentration in deep ocean waters (4000 meters) decrease as the deep waters move from the North Atlantic to the North Pacific?

Microbial respiration along the 2000-year journey from Atlantic to

Pacific.

Why is CO 2 low in the surface ocean?

Photosynthesis in the surface ocean

How much of the cumulative CO 2 emitted to the atmosphere from fossil fuel burning has the ocean taken up?

About 30%

The ocean surface is 60% more acidic today relative to the pre-industrial level.

False

What will happen to the acidity of the surface ocean if you bring deep ocean water to the ocean surface?

Acidity of the surface ocean will increase.

Oyster aquaculture on the west coast of the United States will begin to be impacted by ocean acidification in 20-30 years

False

Why are polar seas especially vulnerable to ocean acidification?

Cold water can absorb more CO2 than warm water.

With “business-as-usual” fossil fuel emissions, how soon will polar seas become corrosive to the calcium carbonate shells used by planktonic organisms that form an important part of the base of marine food webs?

20-30 years

When we finally stop burning fossil carbon and emitting the CO2 to the atmosphere, ocean acidity will remain elevated for 10,000 years.

True

How were heavy elements like carbon, nitrogen, copper and gold created?

All heavy elements were created inside of stars or when stars exploded.

How do stars form?

Stars started forming after the intense heat of the Big Bang cooled and cold hydrogen gas began condensing into large-mass objects due to gravitational attraction. When an object’s mass becomes very large, the gravitational compression within the center of the object makes its interior hot enough to ignite thermonuclear fusion reactions.

How was our moon formed?

An ancient planet the size of Mars hit the Earth, and the ejected material that subsequently coalesced to form the moon.

Our understanding of where the water that fills the Earth’s oceans came is still of some scientific debate, but most scientists currently think it was likely brought to earth by comets.

False

If you scaled the Earth down to the size of a beach ball (half meter diameter), how thick would the ocean be?

About 0.1 millimeter

How quickly did life appear on Earth after the Earth cooled and the oceans filled?

Remarkably quickly (less than 500 million years).

When did life on land first appear?

550 million years ago

Which animal group represents the first appearance of a backbone that evolutionarily led to you?

The first vertebrates were fish.

What is the nature of the earliest known fossil?

A Chemical Fossil

When did life on Earth transition from being just simple prokaryotic organisms floating around in the ocean to more complex eukaryotic organisms and multicellular organisms?

About 2 billion years ago

Which came first, evolution of bacterial photosynthesis and the associated production of oxygen or the evolution of multicellular organisms?

evolution of bacterial photosynthesis and oxygen came first.

What was the Cambrian Explosion?

An event in Earth history where most of the major animal phyla were created in a relatively short period of time.

What is the geologic age (period) of the rocks around Ithaca?

Devonian

Which type of crust is denser?

Oceanic Crust

What evidence did Alfred Wegner use to confirm that the continents had drifted over geologic time?

Fossil and mineral belts on separate modern-day continents aligned neatly when the continents were artificially moved into a single super-continent.

Why was extensional faulting along the axis of mid-ocean ridges an important piece of evidence leading eventually to the development of plate tectonic theory?

Because extensional faulting occurs when solid rock is pulled apart.

What kind of tectonic process takes place in deep sea trenches?

This is where old oceanic crust is sinking back into the mantle.

How are continents moved around on Earth over geologic time?

Continents are moved when the tectonic plates that they are a part of move.

Which geologic feature is a result of oceanic crust colliding with continental crust?

Andes Mountains

Why is the age of continental crust so much older than the age of oceanic crust?

Ocean crust is constantly being made at mid-ocean ridges and then recycled back into the mantle in subduction zones.

How were the Hawaiian Islands created?

Mantle hot spot that upwelled magma to the surface to form underwater mountains that eventually grew to become islands.

Where are siliceous and calcareous oozes typically found?

Away from coasts in regions of high biological productivity.

Analysis of fossil shells in sediment cores extracted from the sea floor can yield information about:

All of the above

Which wave process gives rise to the nice, clean sets of waves that have similar wavelength that come ashore in Hawaii from Alaskan storm?

Wave dispersion

What typically happens to wave energy as it approaches a coastal headland?

The wave energy is focused to produce larger waves.

If you are caught in a rip current, what should you do?

Swim along the shore for 10 to 20 meters, then back to shore, and then call Bruce.

What is a storm’s fetch?

It is the diameter of the storm system.

How fast does the tsunami wave propagate?

About 500 miles per hour

What should you do if you were somewhere near a beach and suddenly felt a small earthquake?

You should move immediately to higher ground or a tall building.

In the video of the Japanese tsunami propagation across the Pacific that was shown in class, which of the following best expresses how the wave propagated?

A great many waves generated near the coast of Japan – similar in nature to throwing a large handful of small rocks into a pond. These many individual tsunami waves spread across the Pacific where they formed a highly complex pattern of constructive and destructive wave addition.

Which force is involved in the creation of the tidal bulge located on the far side of Earth

that is opposite from the side facing the moon?

Centrifugal force

What orbit path does the moon take around the Earth?

The moon’s orbit around the Earth is at a 28° inclination relative to the equator.

When do Spring Tides occur?

During a full moon

Why do we get rotary tides?

The combination of Coriolis force and blocking by continents.

Why do you not get a significant tidal range in Hawaii?

Hawaii is near an amphidromic point

If you have high pressure at 30ºN and low pressure along the equator, why do the surface winds not move in a straight line southward from high to low pressure? Why do they instead turn to the west?

They are turned by the Coriolis force.

Does the mixing depth of the surface ocean get shallower or deeper as you transition from winter into spring and summer in temperate (mid-latitude) regions?

The mixed layer gets shallower as the surface layer warms because the warmer water is more buoyant and, thus, it is more difficult for the winds to mix the surface water to greater depth.

What is Ekman Transport?

The movement/transport of a relatively thin (c.a., 50 meters) slab of surface water that occurs in direct response to wind forcing.

How is the mound of surface water in the middle of the subtropical gyre formed?

The action of the Trade Winds and the Westerly Winds collectively drive an Ekman Layer convergence into the middle of the subtropical gyre.

What drives subtropical gyre rotation?

A center of high pressure under a mound of water drives ocean currents radially outward and these currents are deflected by the Coriolis Force.

If winds are blowing from north to south along the west coast of the United States (e.g., the Washington, Oregon and California Coasts), would the Ekman Layer move onshore or offshore?

Offshore

How is the age of bottom water in the deep ocean measured?

Based on ¹⁴C concentration

How long does it take for deep ocean water to move from the North Atlantic to the North Pacific?

About 2,000 years

The reason oceanographers care so much about the movement of the conveyor belt circulation is because:

It moves a lot of heat from the equator to higher latitudes.

Which statement best describes the current state of scientific knowledge regarding the possibility that the Atlantic Meridional Overturning Circulation (AMOC) might collapse this century?

Scientists have modest but steadily growing concern that AMOC could collapse this century.

What happens to the Walker Circulation Cell during the transition from normal conditions to El Niño conditions?

The Walker Cell slows down or reverses.

What happens to the Warm Pool during the transition from normal conditions to El Niño conditions?

The Warm Pool propagates from the Western Pacific (near Australia) to the Eastern Pacific (near Peru).

During an El Niño event, biological productivity off the California coast can be expected to increase?

False, El Niño events typically lead to a decrease in primary production that, in turn, lowers growth for the rest of the food web.

How can the effects of El Niño conditions in the Pacific be transmitted to the far reaches of the globe?

Variation in the position of the Jet Stream in the atmosphere

What happens to the global-average temperature during an El Niño year?

Global temperatures increase during an El Niño year.