This
section is divided into 3 parts; Who, How
and Why
"How inappropriate to call this planet Earth, when clearly it is Ocean.
" -- Arthur C. Clarke
The oceans account for 70% of the Earths surface, have 99% of the Earth's living
space which is occupied by 95% of all life on the planet. It is where life began
and where the first 3.5 billion years took place. Seventy percent of the oxygen
produced by photosynthesis occurs in the ocean. Forty percent of the human population
live within 50km of the ocean and use it as a resource, with one sixth of the
population using marine life as their principal source of protein. While, there
can be water without life, it is impossible to have live without water. To understand
the history and nature of life on Earth you first must understand oceans and
the marine environment.
Throughout human history we have endeavored to understand our environment for
no other reason that our own curious natures. By understanding our environment
and its history we better understand ourselves. The oceans provided one of the
most fascinating areas of scientific inquiry, for life on Earth began there
and the first 3.5 billion years of evolution occurred there. By the time life
moved onto land in the late Silurian period, almost all the important evolutionary
step had been completed, such as animals being quadrupeds. Another important
process that has affected all life on the planet though out time is plate tectonics
and continental drift. To find the driving forces behind the motion of plates
we must again look to the oceans and the oceanic floor itself.
The first evidence for life on Earth comes from North Pole in the Yilgarn Block in Western Australia and dates back 3.56 billion years. Cellular remains of single cell organisms known as prokaryotes are preserved in structures known as stromatolites. Prokaryote are very small (<20 microns) and have no organised nucleus or other complex internal structures - prokaryote is Latin for before nucleus. The prokaryotes formed large mats in on primordial tidal flats. When the mats occasionally became covered with sediment the prokaryotes grow through it trapping a layer of mud and sand. In this way stromatolites were formed and added evidence to early life on the planet to the fossil record. Stromatolites still exist and can be seen slowly growing in Shark Bay, Western Australia.
v Stromatolites grow
on a primordial shoreline during the Precambrian. Ralph E. Taggart.
For the last 300 years sciences and philosophers have documented fossils that
occur in sedimentary rocks. A sedimentary sequence of rock contains layers the
represent the passage of time. By documenting fossils that occur in progressively
high and younger layers of the sequence we can see how life on the planet changed
with time. Charles Darwin's study of the fossil record as well has his own observations
of breeding programs in domestic animal led him to formulate the theory of evolution.
Darwin and his fellow naturalist Alfred Wallace independently came to the conclusion
that geologically older species of life gave rise to geologically younger and
different species through the process of natural selection. The process of natural
selections leads to the evolution of species that adapt to different or changing
environmental conditions. Those species that do not adapt to changing environment
become extinct.
In the period between the earliest beginnings of life ~3.5Ba to the late Silurian
~410Ma, there was little or no oxygen in the Earth's atmosphere and the planet
was without an ozone layer capable of filtering out harmful UV radiation from
the sun. Therefore, life could not exist on land, but only in the sea where
water filtered out the deadly the UV. The first 93% of the evolution of life
on Earth occurred in the oceans. To understand the evolution of life from its
early beginnings until present day we must also understand the history of the
environment where most of it occurred - the ocean.
>
The first evidence of life on Earth - a stromatolite
form North Pole, Australia.
People have recognised that the continents seem to fit together for at least
400 years, but it was not until extensive ocean floor mapping was achieved in
the 1960's that the theory of Plate Tectonics was taken seriously. In the 1600's
Sir Francis Bacon wrote that the coastlines of the continent seem to fit nicely
together. In 1912 Alfred Wegener proposed that the continents were once joined
together in a super continent called Pangaea, which broke up during the Carboniferous
and the continents then drifted to where they are today. However Wegener lacked
a mechanism is his theory of Continental Drift so it was initially greeted with
hostility. Dr. Rollin T. Chamberlin of the University of Chicago said, "Wegener's
hypothesis in general is of the footloose type, in that it takes considerable
liberty with our globe, and is less bound by restrictions or tied down by awkward,
ugly facts than most of its rival theories." Wegener's idea went almost
unnoticed until 1929 when Arthur Holmes theorised that thermal convection in
the mantle acted like a conveyor belt that moved continents around. Again without
proof the idea languished. It wasn't until the 1960's that people started taking
the idea of Plate Tectonics seriously. Improvements in sonic depth recording
during World War II and the subsequent development of the nuclear resonance
type magnetometer led to detailed mapping of the ocean floor. Geophysics R Deitz
(1961) and Harry Hess (1962) noted geomagnetic patterns in the ocean floor mirrored
either side of mid-ocean ridges and developed the idea of sea-floor spreading.
<
Alfred Wegener ponders the jigsaw puzzle of the continents.
USGS
Much of what we now know about plate tectonics come from the oceans. The two main driving forces can be found at mid-ocean ridges and trenches, both within ocean basins. Mid-ocean ridges are gigantic submarine mountain ranges that rise 3000m above the sea floor and are 2000 km wide. The are produced by upwelling mantle, which lead to volcanism and the creation of new sea floor. This process combined with gravitation sliding of oceanic plates on either side of the ridge push plates away from the ridge. The bulk of what we know about sea-floor spreading comes for oceanographers observations of the bathometric, seismic, magnetic and thermal properties of the ocean floor near mid-ocean ridges.
While ocean floor is created at mid-ocean ridges, it is consumed
in oceanic trenches. Old, cool, dense oceanic plate is heavier that mantle that
it overrides. Trenches up to 11km deep form when old oceanic plate collides
with another plate and begins to sink into the mantle. This process is known
as subduction. Once subduction begins it become a cell propagation phenomena
as the density of the subducting slab is increased by metamorphic processes
that in turn pull more oceanic plate down with it.
^ Earthquake frequency
in the Atlantic Ocean is focused on the Mid Atlantic Ridge and is related to
sea floor spreading. From the National Oceanic and Atmospheric Administration
(NOAA).
Plate tectonics and evolutionary theories are draw together when ancient oceans
are considered. One of evolutions driving forces is the environment change which
can lead to the rapid proliferation of species (Cambrian Explosion) and some
times catastrophic mass extinctions (Permian Mass Extinction) Plate tectonics
has a critical role in the ocean environments as it controls the size and shape
of ocean basins which in turn control circulation within them. An example of
how plate tectonics effects evolution of life is the Permian Mass Extinction
when 90% of all species in the ocean were wiped out. At this time all the continents
in the world came together to form one supercontinent called Pangaea. The amalgamation
of Pangaea radically changed the circulation of deep ocean currents and resulted
in the reduction of shallow marine environments. These factors contributed to
the mass extinction event (as did global volcanism and the resulting 'nuclear
winter'). The study of ancient oceans (Tethys Sea) is known as paleoceanography.
Paleoceanographers use geophysics, numerical modeling and fluid inclusions in
crystals to determine the size, structure and chemistry of ancient oceans. In
doing so they make an important contribution to the debate on global climate
change, but more about that later.
The accretion of Pangaea in the Permian with the ancient
Tethys and Panthalassic Oceans. From the USGS.
The ocean and the atmosphere form a coupled system that controls the climate
of the planet. They exchange energy as heat and momentum and they effect each
other's chemistry with the exchange of water through precipitation and evaporation,
and also exchange of gases such as CO2. The oceans are capable of storing large
amount of heat and then releasing it, sometime at a different place. This ability
tends to moderate the global environment as heat is absorbed when the atmosphere
is hot, and released when the atmosphere is cold. This process occurs diurnally,
seasonally and over years. Similarly, the oceans can store and release CO2.
Through these processes, the state of the ocean effects the climate of the planet
on all geographic and time scales. An example of a short-term effect of the
oceans on the climates of continents is the El Nino effects that can course
drought and bush fires in Australia and catastrophic flooding in South America.
The El Nino is the abnormal warming of the surface layers of the eastern tropical
pacific, which occurs on the time scale of years to decades. The warming of
this region of the ocean results in high rainfall over the America's and the
breakdown of the Peruvian Up-welling leading to the decimation of fisheries
west of South America. "El Nino" means "The Christ Child"
and was given to the phenomena by South American fisherman as the cycle begins
around Christmas time. While South America experiences high rainfall, on the
opposite side of the Pacific eastern Australia experiences drought conditions.
The heat budget, circulation patterns and CO2 contents of the oceans also effect
the global climate on the time scale of hundreds of years to millions of years.
An example how circulation pattern and heat flow can effect climates on a large
time scale is the shutting down of the Gulf Stream 13 000 years ago. The Gulf
stream transports warm equatorial water from the Gulf of Mexico to the west
coast of Europe and considerably moderates the climate of Europe (it would be
much colder without it). As the water moves north, evaporation make the water
more saline and denser so that it sinks off the Norwegian coast. This is a major
contribution to the global circulation pattern. Around 13 500 years ago fresh
water from melting glaciers spilled through the St Lawrence River into the North
Atlantic diluting the dense saline water so that it would no longer sink and
the Gulf Stream broke down plunging Europe into a mini-ice-age. This only took
~150 years and should be considered as an important lesson to those living today
- global climate change can happen incredibly quickly.
<
The Gulf Stream. Melt water from glaciers in North America
moved down the St Lawrence River and shut down the Gulf Stream 13 500 years
ago. -from NSF
A similar situation could arise in the next decades if a rise in the mean temperature
of the Earth via The Greenhouse Effect resulted in the melting of the polar
ice cap. Carbon dioxide makes up around 85% of greenhouse gases emissions that
result from human activity and the level of CO2 in the atmosphere has risen
by 25% since the industrial revolution. A major natural reservoir of CO2 is
the ocean, which absorbs vast amounts of CO2 from the atmosphere in polar regions.
Marine Scientists are currently considering ways of increase this natural uptake
of CO2 by pumping CO2 emission directly into the deep ocean 1000-3000m. Other
marine scientists have pointed out that this would increase the acidity of the
ocean and may have other long term detrimental side-effects. Others have considered
fertilising the ocean surface with iron to promote plankton growth and increase
photosynthesis. Experiments on iron seeding are currently being conducted in
the Southern Ocean (CARUSO experiment - CARbon Uptake in the Southern Ocean
- can't have a save the world project without a spunky anagram).
One possible effect of global warning is sea level rise, which would occur via the thermal expansion of the ocean and the melting of the polar ice caps. A rise in the temperature of the ocean might result in the breakup of the Ronne/Filchner and Ross ice- shelves, which serve as a barrier to the west Antarctic Ice Sheet. The melting of the ice-shelves would not lead to sea level rise because the ice already water in the ocean. However, the melting of the west Antarctic ice-sheet would lead to a sea level rise of 8 meters. If the Greenland ice-sheet also melted then the sea level would raise another 6.5m. However, the main contribution to sea level rise is thermal expansion of the oceans. Climatologists estimate that the mean temperature of the planet has risen 0.5° in the last century. Based on tide gauge measurements marine scientist believe that the expansion if the oceans due to this temperature increase has led to the level of the ocean rising between 20cm and 40cm.
.
Modeled sea level rise from 1765 to 2100 based on a future where the way we
treat the planet doesn't change for the way we currently do. The uncertainty
range is for uncertainty in the climate sensitivity only. From The Climatic
Research Unit at the University of East Anglia.
Much attention has been paid to terrestrial biodiversity, but sadly the same can not be said about this in the marine environment. This is in part do to the difficulty of studying marine systems, but it is in some ways surprising given that the oceans account for around 99% of the planets 'living space'. Life of the planet can be subdivided into the five kingdoms and further subdivided into phylum. There are 33 phylum recognised on earth of which all but one is found in the ocean and 15 are only found in marine ecosystems. The oceans have a diversity that is far greater than the land. An example of how rich the diversity of the oceans are can be seen in the Great Barrier Reef where there are 1,500 fish species (8% of all known fish species, more than 700 species of coral, over 4,000 species of molluscs and 252 species of birds, which nest and breed on the coral cays.
Biodiversity with in the oceans is under grave threat, mostly from human activities. Many factors are resulting in the extinction of marine species, which include direct habitat destruction through the erection of engineering and drainage works, poor or uncontrolled fisheries management; the introduction of alien species; and the pollution of the oceans.
Biodiversity is incredibly important because life changes to meet environmental change through natural selection and evolution. When biodiversity is reduced the pool from which natural selection can occur is diminished and proper adaptation to our rapidly changing environment can not occur. The oceans also provide an important source of raw materials that can be used for food, medicine and building materials. Thus, reducing the amount of species in the oceans will certainly have a detrimental effect on humans. Finally, ecosystems are one of the most important factors that control the global climate. The biogeochemical cycling of gases is greatly controlled by the living biota existing on earth of which the marine realm is extremely important. Marine science helps us better understand the biodiversity of the oceans, and may also help us preserve it for our own good.
Man and the marine environment interact directly along coasts. Forty percent of the world population live within 100km of coasts. Coastal management is even more important in Australia where 85% of the population live close to coasts. People use the coastal environment recreational and exploit it economically. It is important therefore that we preserve and maintain our coastal and estuary environments by proper management of fisheries, preservation of sea grass beds, and beach replenishment. Also critical are the management of pollution and water run off, and the planning of tourism and other commercial and residential planning.
The oceans have long been an important economic resource for humans. People have throughout their history utilised fisheries and now also exploit marine related mineral and fuel deposits. Marine scientists also contribute to the global economy via long-term weather forecasting important to agriculture, navigation that is critical to maritime services and increasing the understanding of hazards such as tsunami and severe storm.
The earliest evidence we have of people exploiting the ocean for food are shellfish remains found in Italy which date for 140 000 years ago. Aboriginal communities where using fish nets to catch fish at least 25 000 years ago (evidence from Willendra Lake), the oldest fish hooks are found in Europe and date back 14 000 years ago and coastal Danish communities were exploiting the oceans by the Mesolithic Period (c. 9300-3900 BC). Whaling commenced in the first few centuries A.D. by the Japanese and around 800 A.D. by the Norwegians and Basque people. Sadly both the fishing and whaling industries have a history of overexploiting their resources.
Marine science plays an important role in monitoring and regulating fisheries. Whaling was first regulated in 1946 by the International Whaling Commission (IWC), which gave member nations quotas on the whales based on negotiations and guesswork. Unfortunately the quotas were always too high, so the populations declined rapidly. Once the largest Blue whale were hunted to the point that they become so rare that whalers could no longer find them, they moved on to the next largest the fin whale, and then Sei, and then Minke. By the 1970's, many whale species were hunted almost into extinction. In this period many non-whaling nations joined the IWC and in 1982 voted for an indefinite moratorium on commercial whaling, which became effective in 1986.
The fishing industry has a worse record of over-exploitation than the whaling industry. Many important economic species have been hunted close to extinction, which include:
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Marine environments are associated with many types of important mineral and petroleum deposits. Among these are hydrothermal deposits, placer deposits, banded iron formations and greenstone deposit.
Hydrothermal deposits are associated with mid-ocean ridges. The high heat flow at mid-ocean ridges set up convective cycles within the oceanic crust where seawater is sucked into the crust through fractures, is heated at the oceanic ridge and then expelled back into the ocean. As the seawater is pumped through the crust it dissolves metals such as Mn, Ni, Fe, Cu and Pb. As the water moves back towards the surface it cools and the metal precipitate as sulphides and are pumped into the ocean where they are deposited on the sea floor. This process can be seen as "black smokers" near mid-ocean ridges. Such deposits can be found within the ophiolites of Troodos in Cyprus and Semail in Oman where they occur as manganese nodules
< Sulphides pouring into the ocean at ~350°C.
- from USGS. Banded Iron Formations from in between 2500ma and 1800 Ma,
at a time when there was little or no oxygen in the Earth's atmosphere. Iron
released from weathered rock on land did not oxidise and it does now (rust),
and was washed into the ocean in its ionic form. Once in the ocean it was oxidised
by the oxygen photosynthesised by algae and precipitated out as magnetite (Fe3O4).
This was great for the algae as oxygen was waste produce for them and quite
toxic, the iron effectively cleansed their environment. A clean environment
led to a bloom in the algal population, the complete consumption of all the
iron, followed by the build up of oxygen which killed all the algae. This process
first lead to the deposition of a layer of iron ore, then a layer of silica
(chert).
The Archaean aged greenstone belts of Western Australia and Canada contain rich
gold fields. The geology of greenstone belts is very complicated due to their
deformation, metamorphic and igneous histories. However, the generally developed
from or on oceanic crust or back-arc basins and probably over subduction zones
like the Andes Mountains.
Placer deposits are formed when minerals (gold) or gems (diamonds) are transported
by currents or rivers. The relative high density of precious metals and gems
means that lighter particles get washed further away. Commonly light material
is washed out of joints in the ocean floor leaving deposits of precious minerals
or gems.
Hydrocarbons deposited ocean basins are an incredibly important source of fuel and material form chemical industries. Organic matter that is deposited with fine sediment in deep marine environments from shales and mudstones that become source rock for hydrocarbons. When the rocks become overlaid by further sediment and are pushed down into the Earth's crust where they are heated to between 70°C and 130°C they produce oils and gases. These rise through the sedimentary pile and may become trapped in porous sandstones that from reservoir rocks. Evidence for these sets of events are sought using seismic and drilling programs, as they may lead to the exploitation of rich gas and oil fields.
As has been said, the ocean and the weather have a strong link. By better understanding the ocean it is possible to make long term weather forecasts. Ocean currents and surface temperatures greatly effect the season weather of continents. An example is the monitoring of the Southern Oscillation, which are the high and low pressure systems of the west and east Pacific respectively. The intensity and direction of the southern oscillation is directly link to the El Nino cycle making it possible to inform farms of on coming drought in Australia. The extended dry periods associated with severe El Nino cycles can also increase the likelihood and intensity of bush fires on the east coast of Australia. An example is the very bad El Nino cycle was that of 1982-3, which resulted in the savage drought of the same period, the dust storm that effected Melbourne and the Ash Wednesday bush fires of February 16th 1983, which killed 75 people and burnt out area the size of Metropolitan Sydney in only 8 hours.
Apart from forecasting droughts and bush fire likelihood, the study of the
ocean also helps us forecast the chance of other natural hazards such as king
tides, tsunamis and severe weather events such as cyclones. Tsunami are deep
ocean waves generated by earthquakes, explosive volcanism and comet impacts.
The enormous amount of tectonic energy released by earthquakes results in a
fast moving wave (800kph!) that extends from the surface to the bottom of the
ocean (as opposed to just the surface layer as is the case with wind waves).
The size of the waves become magnified as they reach coastlines and can do great
damage. The largest observed tsunami was caused by the 1883 eruption of the
Krakatoa and reached a height of 35m. It killed 36,830 people. A potentially
disastrous tsunami would be caused by the impact of a stony asteroid into the
ocean. An asteroid of 500m diameter would produce an 11m wave over deep ocean,
which would magnify by around ten times as it approached nearby coastlines.
< A tsunami breaks over the pier of Hilo, Hawaii,
on 1 April 1946. The man watching it was one of 173 fatalities in the Hawaiian
islands. Photo: NOAA.
The understanding of ocean currents, bathymetry and the relationship between the oceans and weather has always been important to mariners, be it for navigation or storm forecasting. With the introduction of the telegraph marine cables have connected island to mainlands, and continents to continents.
As the world seeks to reduce the emissions of CO2 from the burning of fossil fuels, alternative energy sources are becoming increasingly important. One possible source of energy is the kinematic and heat energy of the ocean. Kinetic energy from waves can be harnessed by using its up and down motion to push air in a cylinder through turbines. Tidal energy could also provide energy by trapping water from high tides behind dams, then expelling the water at low tide through turbines much like a conventional hydroelectric dam. Several tide generators are operational already, with one in France generating enough power to supply 240 000 homes. Several test plants in Japan are also trying to harness thermal energy in the ocean by exploiting vertical temperature differences.
<Converting wave
energy into electric energy. From the California Energy Commission.
Who? |
The origins of marine science |
How? |
Methods and techniques for sampling the ocean floor |
Some of the terms, events, people and equipment associated with Marine Science.
In the three sections of this section, a myriad of instruments have been discussed. Obviously, the best way to become familiar with what can, can't and should be done with each one is best discovered by actual application. This, hopefully, is the next best thing - a hybrid of practical and theoretical application.
A bit of a no-brainer, but any exposure to 'nollige' is good exposure.
Additional information to allow you to test some of the ideas and concepts from this chapter.
- continental jigsaw?
- Challenger Path?
Sampling-type problems?
We realise that not everyone has had experience with the intrinsic concepts of Marine Science. This 'computer' has numerous examples which will help you understand these fundamental facets! Very helpful, very colourful!