exploring oceans Flashcards
what is an ocean?
a body of saline water that composes much of a planets hydrosphere
how much of the earth’s surface do oceans take up?
71%
what is an ocean basin?
a depression of the Earth’s surface in which an ocean lies
what are seas?
seas are smaller than oceans and are located where land and oceans meet
rank the oceans from largest to smallest?
pacific, atlantic, indian, southern, arctic
what is the continental shelf?
the gently sloping offshore extension of a continent extending into the ocean as far as the continental slope
average 70km long, slope angle 2m/km
what is the continental slope?
where the continental shelf becomes steeper as it descends to the deep ocean
average 16km long, slope angle 70m/km
what is the abyssal plain?
the deepest part of the ocean covering vast areas of ocean floor. Submarine mountain chains and trenches interrupt the relatively flat plain
deep (2000m+) and vast with many features
what is an ocean trench?
formed when one tectonic plate subducts beneath another as they collide.
the oldest (therefore densest) plate will subduct
the subduction zone becomes one of the deepest parts of the ocean
what is a guyot?
a peak that once rose above the surface of the ocean. Erosion then reduced their height below sea level, leaving the peak with a flat top
what is a sea mount?
any form of underwater mountain
it is a volcanic peak rising steeply from the ocean floor.
Some are isolated while others occur in chains extending from a mid-ocean ridge or hot spot
what is the salinity of freshwater compared to seawater average?
freshwater = >0.5ppt
seawater average = 35ppt
what parts of the world have higher salinity and why?
Atlantic and Mediterranean bc they are more landlocked and ocean currents circulate the water less
which parts of the world have lower salinity?
the polar regions bc freshwater from ice dilutes salt water. salt water also sinks and move away
why does the Mediterranean Sea have a particularly high salinity?
not much of an ocean current to circulate and dilute the water
landlocked
hot so more evaporation
why is the sea salty?
because of black smokers underwater
what is thermocline?
the depth in the ocean where there is a rapid change in water temperature
cold water is dense, and dense water sinks
water temp decreases rapidly as depth increases close to the surface. this is known as the thermocline. the depth of the warm surface layer varies both with season and location. Generally, below about 1km, water temperature hardly changes with increasing depth
what is the halocline?
the depth in the ocean where there is a rapid change in the salinity of seawater
high salinity makes water denser, dense water sinks
how does the ocean vary vertically?
differences in density affect water movements, such as the flow of ocean currents that move heat from the tropics to the poles and affect global climate
density changes in different layers of water affect how, when and where water moves vertically in oceans
what is the (eu)photic zone?
sunlight rarely goes beyond this area
all marine organisms that photosynthesise are limited to the photic zone. this includes phytoplankton
90% of marine organisms, live in, or are frequent visitors to the photic zone
what is the dysphotic zone?
sunlight decreases rapidly with depth
photosynthesis not possible here
what is the aphotic zone?
sunlight does not penetrate at all
makes up the majority of the ocean
has a relatively small amount of life both in diversity of species and in numbers
what is bioluminesence?
the ability of some organisms to generate light from their bodies
at a depth where light reaches some organisms use bioluminescence to create their own light to lure prey/ evade predators
what are some examples of nutrients needed by organisms?
nitrogen, iron and zinc
how do nutrients enter the ocean?
dissolved nutrients from weathered rocks are transported by rivers into the oceans and from dust carried by winds
plankton incorporate nutrients into their tissues,and those are then passed through ecosystems as consumer organisms feed on plankton and each other
where are nutrient levels low?
nutrient levels are relatively low at the surface, especially away from continents where rivers flow into the ocean to bring dissolved minerals
warm waters in equatorial regions are also low in nutrients
how is the Sun’s energy transferred down from the surface?
by marine snow falling
this is made up of small particles, the remains of organisms living near the surface
what is a hydrothermal vent?
very hot water springs, rich in dissolved minerals, flowing from the ocean floor at mid-ocean ranges or hot spots
these are rich in silica, manganese, hydrogen, sulphur and methane. Specialised bacteria fix the energy from these erupting smokers and communities develop unlike any other on Earth
organisms such as tube worms, shrimp and small crabs obtain their energy from the chemical energy in hot water
changes in nutrient levels
- a variety of nutrients are needed by all organisms]
- dissolved nutrients from weathered rocks are transported to sea via rivers and wind
- phytoplankton incorporate these nutrients and they are passed thru food chain
- nutrients are returned to water through waste products and when they die
- nutrient levels are lower at the surface (away from continents) as they are quickly used or sink
- once they sink they are unable to return to the surface due to density (thermocline) unless there is an upwelling
- upwelling occurs in Southern OCean and around Antarctica at certain times of the year
what is the ocean ridge?
the point at which the plates separate and a new crust is formed
what is the ocean rift?
hills and valleys that form around the ridge
what is sea floor spreading?
the formation of fresh areas of oceanic crust which occurs through the upwelling of magma at mid-ocean ridges and its subsequent outward movement on either side.
what are the two types of ocean current?
- movement of surface water (approx top 400m)
- movement of deeper water (around 90%)
what are ocean currents a result of?
solar heating, effects of wind, gravity and the Coriolis force
what are surface currents?
(how they are formed)
- solar heating causes water to expand, creating a slight slope away from the equator which water will run down
- prevailing winds will push the water to flow in that direction. Will pile up water in direction of wind and gravity, encouraging water to move downslope
- coriolis force causes water movement to be deflected by the spin of the earth, creating larger currents known as gyres
why is the climate in Western Europe warmer than other areas at similar latitudes?
the Gulf Stream carries warm water northward from the tropics
what is the thermohaline circulation?
currents that run deep into the oceans
what is Net Primary Productivity? (NPP)
a measure of how much of the Sun’s energy is captured
usually measured as grams of carbon per unit area per year
what is the total NPP?
100 billion tonnes of carbon
just under half of this occurs in the ocean, a key part of the carbon cycle
where is the highest NPP found?
where the supply of dissolved nutrients is highest, around coasts
kelp forests can have NPP approaching what is found in tropical rainforests, and seagrass meadows and floating seaweeds play important roles
where are areas of low NPP?
large areas of the ocean away from continents have low nutrient levels and low NPP
what is the intertidal zone?
the area that is above water at low tide and underwater at high tide
the area can be a narrow strip, as in Pacific Islands that only have a narrow tidal range, or can include many metres of shoreline where shallow beach slopes interact with high tidal excursion
what are typical inhabitants of the intertidal zone?
urchins, sea anemones, barnacles, chitons, crabs, isopods, mussels, starfish etc
an example of an intertidal food chain?
sea weed - phytoplankton - mussels - crab
what are two extreme environments in the deep sea where life is more abundant?
cold seeps and hydrothermal vents
food chains here do not begin with plants or algae that make food from sunlight
what are cold seeps?
where methane and hydrogen sulfide are released into the ocean
what organisms reside in cold seeps?
home to clams, mussels, shrimp, crabs, bacteria and tubeworms
for food, these animals depend on certain types of single-shell Archaea and Eubacteria microbes that live off the methane and hydrogen sulfide from the seep
what organisms reside near hydrothermal vents?
certain types of Archaea and Eubacteria microbes are able to turn the chemicals from the hot water into the energy they need to survive
many other types of living fish eg fish, shrimp, giant tube worms and crabs thrive in this environment
some, like mussels and clams, get the nutrition they need from microbes living in their bodies. others, like shrimp, eat the Archaea and Eubacteria
example of a deep water food chain?
tube worms - mat forming Bacteria - Zoarcid Fish - Octopus
compare inter-tidal and deep water ecosystems
intertidal has more light, deep water is always dark because sunlight cannot get down that far
intertidal zone is close to the coast so has lots of nutrients. deep water has lower nutrient levels
why is there more oxygen able to dissolve into the ocean near Antarctica?
surrounded by the Antarctic circumpolar surface current. the cold water allows more oxygen to dissolve in the ocean, which is an advantage for marine life
when is phytoplankton activity highest in Antarctica?
during the summer (Nov-Mar), when there are fewer than 12 hours of sunlight and more than 20 hours for several weeks, therefore the surface waters in the ocean around Antarctica are rich in nutrients?
what process is the entire ecosystem in the ocean around Antarctica built upon?
as sea ice forms at the start of winter, some salt is expelled from the ice in the surrounding water
the more saline water becomes, the more dense the surrounding water
the surface water is cooled to below 0 degrees C, bc saline water has a lower freezing point than freshwater
very cold saline water at the surface sinks
less salty and therefore less dense deep water upwells, carrying nutrients such as nitrogen and silica
phytoplankton use these nutrients to grow
the entire ecosystem builds on this process
what are marine food webs and chains like in the oceans around Antarctica?
relatively simple, and biodiversity is comparatively low
eg one food chain starts with phytoplankton. krill feed on these and are in turn eaten by baleen whales
what are the pros of whaling?
whales provide meat, blubber and skins, all of which can be used
what is whale blubber mainly used for nowadays?
today, meat is the primary product of sale
blubber had been rendered down mostly to cheap industrial products such as animal feed or, in Iceland, as a fuel supplement for whaling ships
what are the cons of whaling?
- the Inuits have hunted and used whales for centuries, but with increased numbers of people on the planet + growing demand for resources, whales have become a threatened resource
- killing animals poses ethical issues
- disturbs ecosystems and food chains
what is the IWC?
International Whaling Commission
was set up under the ICRW to decide hunting quotas and other relevant matters based on the findings of its Scientific Committee
Non-member countries are not bound by its regulations and conduct their own management programs
what countries have urged the IWC to lift the ban?
Japan, Norway and Iceland
what was the compromise plan offered by a coalition of anti-whaling nations?
would allow these countries to continue whaling, but with smaller catches and under close supervision
would also completely ban whaling in the Southern Ocean
who is opposing the compromise plan?
more than 200 scientists and experts have opposed the compromise proposal for lifting the ban, and have also opposed allowing whaling in the Southern Ocean, which was declared a whale sanctuary in 1994
opponents want to see an end to all commercial whaling, but are willing to allow substinence level catches by indigenous peoples
what were the events that led to Iceland leaving the IWC in 1992?
iceland did not object to the 1986 IWC moratorium
between 1986 and 1989, around 60 animals per year were taken under a scientific permit. however, under strong pressure from anti whaling countries, who viewed scientific whaling as a circumvention of the moratorium, Iceland ceased whaling in 1989
following the IWC’s 1991 refusal to accept its Scientific Committee’s recommendation to allow sustainable commercial whaling, Iceland left the IWC in 1992
what was iceland’s quota for the 2012 commercial whaling season?
216 minke whales
how is the IWC effective?
strict quotas which reduces the impacts of whaling
how is the IWC ineffective?
not all countries are a part of the IWC and conduct their own programmes, which could counteract the IWC’s.
Countries can just leave and do what they want, as demonstrated by Iceland
who are the different stakeholders interested in whaling in Iceland?
IWC
whalers
tourists
locals/the government
what are stakeholders?
people or groups that have a vested interest in the activities or events in a local area
how are catch limits decided by the IWC?
the Commission received advice on sustainability from its Scientific Committee and this assists it in deciding catch limits, which are then set out in a document called the Schedule to the International Convention for the Regulation of Whaling (1946)
what is the commercial whaling moratorium?
in 1982 the IWC decided that there should be a pause in commercial whaling on all whale species and populations (known as ‘whale stocks’) from the 1985/1986 season onwards
was implemented as whale hunting was having a significant impact on population numbers and the number of whales were becoming no longer resilient.
the moratorium remains in place today
what are the views of the Icelandic Government on whaling?
claims it was forced to proceed with its rebel whaling program after years of deadlock at the IWC
Foreign Minister is obligated to defend Iceland’s whaling, but has a personal opinion that there is no economic importance of catching 40 minke whales (the quota for that year), and that in doing so it actually harms the tourism industry.
what are the views of the IWC on whaling?
scientists have approved concept of sustainable whaling, but majority of the IWC members disapprove
what are the weaknesses to the government’s view on whaling?
has an impact on tourism
some say whaling is damaging Iceland’s chances of joining the UN Security Council
what are the whalers’ views on whaling, and what are the strengths and weaknesses of this?
think it is good food and a good source of money
S = lots of money
W = they are the reason the whales are dying so much because they commercialise whaling
how is whaling and Iceland’s tourist industry linked?
whale watching brings in 100,000 tourists per year, and people are emotionally attached to the whales
some eat minke whale kebabs
what is commercial whaling like today?
Norway and Iceland take whales commercially at present, either under objection to the moratorium decision, or under reservation to it.
Establish their own catch limits but must provide information on their catches and associated scientific data to the Commission.
Russia also registered an objection to the moratorium decision but does not exercise it.
Norway takes North Atlantic common minke whales within its EEZ
Iceland takes North Atlantic common minke whales and North Atlantic fin whales within its EEZ
where is the Beaufort Sea?
is the portion of the Arctic Ocean located north of the Northwest Territories.the Yukon, and Alaska, and the west of Canada’s Arctic islands
what is the dispute over the Beaufort Sea about?
there is an ongoing dispute between Canada and USA over the delimitation of part of the maritime section of the International Boundary in the Beaufort Sea.
Difference in claims to the maritime boundary creates a wedge that is claimed by both nations.
This dispute has taken increased significance due to the possible presence of petroleum reserves within the wedge. Both nations have put petroleum exploration rights up for bid on sections within this disputed wedge/
what is Canada’s claim with the Beaufort Sea?
claims the maritime boundary to be along the 141st meridian wet, out to a distance of 200 nautical miles, following the Alaska-Yukan land border
what is the USA’s claim with the Beaufort sea?
claims the boundary line to be perpendicular to the coast out to a distance of 200 nmi, following a line of equidistance from the coast.
what is a strength of Canada’s claim?
S = they don’t have as many reserves and so need more