Download Oceans - Sea level change

How will the sea level change over the next
century from various sources (melting of
continental glaciers and ice sheets,and
seawater expansion)?
And what will be the impacts on wildlife and
ecosystems and society?
Hypothesis
As a group we have decided that the sea
level will rise significantly over the next
century due to a variety of factors such as
increase in evaporation and melting of
glaciers. This will not only be detrimental
to humans but will also have a significant
negative impact on wildlife.
Key:
Cesar- red
Maria Jose- blue
Mara- yellow
Piyush- brown
Research
What is sea level?
The sea level, or sometimes called the mean sea level is basically the
average height of the ocean surface. This is calculated by taking the
average of high and low tides of the ocean surface. Scientists who
study the sea level must take into big consideration the rate at which
the sea level rises as it helps obtain more reliable and useful data.
The current sea level increase is 3.1 mm/year.
There are many factors that affect sea level such as the earth’s
temperature, tides and winds; and the change in sea level can be a
measure of climate change and global warming.
Source:
http://www.nasa.gov/vision/earth/environm
ent/sealevel_multimedia_prt.htm
Types of sea level rise
Eustatic sea level rise: This one is affected by climate change and
happens mainly due to global warming. This occurs when sea water
evaporates and it is then deposited onto land through precipitation,
after a certain amount of time it will make its way back to the ocean
however if a glacial period is to occur the water is then trapped in a
glacier and cannot make its way back to the sea therefore changing
the sea level. Vice versa if the glacier begins to melt the sea level
will rise. It can also happen when the ocean basin changes therefore
changing the amount of water it can hold; this happens with tectonic
plate movements. If ocean basins get bigger the sea level will fall,
conversely if they get smaller, sea level will rise. Eustatic sea level
ALWAYS has a global effect.
Types of Sea level rise
Isostatic sea level rise: This happens due to the movement of the
Earth’s crust, during a glacial period the sea would freeze and the ice
accumulated in certain areas would press down on the crust this
caused it to lower the land and sea level due to the weight of the ice.
The same process occurs when the ice melts and pressure on the crust
is less causing it to lift and raise the sea level. It can also happen due
to tectonic uplift or depression however this only havens in plane
boundaries so it can only happen in certain parts of the world.
Change in land level
Due to the fact that the surface of the land, as well as sea, changes
over time the sea level changes are often defined as “relative” or
“absolute”.
“Relative changes may be observed even though the absolute height
of the oceans remains the same.
It is important to realise that when earth scientists talk about a rise
in mean global sea level (what we call ‘eustatic’ sea level), local
changes may be quite different. This is why local studies of sea level
rise and fall are so important.” Sea level has increased an average of
1.7 ± 0.5 mm since the beginning of the 20th century
Post-Glacial rebound
Post-glacial rebound or continental rebound, is essentially the rise of
land mass which was depressed by the great weight of ice sheets
during the last glacial period. This course is called isostasy. This
process began with yet another process called “ice sheet delegation”
which started to occur about 19 000 years ago when most of the ice
sheets found in North America and northern Europe began to melt.
This water formed by the melting commenced to flow into the oceans,
ultimately leading to an increase in sea level. Afterwards, the land
which at one point had been beneath the ice began to rise or
“rebound”; the process called “post-glacial rebound”. This process
continues to take place today. And affects Northern Europe,
Canada,Siberia and the United States.
Post-Glacial rebound graph
In Hudson Bay, as well as in
central Scandinavia the land
is still increasing 1cm a year.
However, areas such as Baltic
states and northern USA are
currently subsiding.
. Courtesy of Tom James at Natural
Resources Canada
http://www.antarcticglaciers.org/
glaciers-and-climate/sea-levelrise-2/sea-level-rise/
Thermohaline Circulation:
Another impact of glacial retreat is the possible effect fresh
melt water will have on the thermohaline circulation.
Driven by density gradients in ocean waters, the
thermohaline (deep ocean overturning) circulation is made
up of the global ocean flow of ocean currents. As ocean
waters move around, different water masses are formed as
evaporation removes fresh water and precipitation and
river runoff add fresh water, each changing the ocean
salinity and therefore the density of the waters. This results
in a change in sea levels.
Diagrams of Thermohaline Circulation:
Image Sources: Left -http://essayweb.net/geology/quicknotes/ocean_currents.shtml
RIght:http://mail.tku.edu.tw/086138/EnvFutures/WebPages/Global%20warming/Ther
mohaline%20Circulation.files%5Cthermohalinemodel.gif
Global Warming
Global warming is the gradual increase in the overall temperature in
the Earth’s atmosphere attributed to the greenhouse effect caused by
excess carbon dioxide emissions, ChloroFluoroCarbons (CFC), and
other pollutants. Ice is melting worldwide, especially at the Earth’s
poles. This includes mountain glaciers, ice sheets covering West
Antarctica and Greenland, and Arctic sea ice.
A rise in global temperature means melting of snow in the poles. This
will result in drastic rises in sea levels. It also causes thermal
expansion.
Other impacts include:
● Increase in precipitation (rain and snow) globally on an average.
● Changes in ecosystems: Some butterflies, foxes and alpine plants
have moved farther north or to higher, cooler regions.
Thermal Expansion
As silly as it sounds; sea level rises due to global warming by the simple fact
that water molecules gain kinetic energy due to heat. The particles in the
upper level of sea are quickly released on to the atmosphere, however those
in the deeper levels of the sea will take longer to be released; keeping them
in the ocean and contributing greatly to seawater warming which causes an
expansion of the total water in the ocean causing a rise in sea level. This
happens because warm seawater has greater density than colder
seawater.The oceans store more than 90% of the heat in Earth’s climate
system and act as a temporary buffer against the effects of climate
change.For instance, an average temperature increase of the entire world
ocean by 0.01 degree Celsius may seem small, but in fact it represents a very
large increase in heat content.
Graph showing the relation between thermal expansion
and melting of land ice in inches per decade. Melting of
land ice is much higher from 1993-2008 as compared to
1972-2008.
Melting of continental glaciers
Glaciers, alongside with ice-sheets
cover up to 10% of the entire
planet's land. The melting and
ablation of glaciers is mainly due to
the increase in temperature as it
affects the overall mass balance of
glaciers and ice-sheets decreasing it
at a fast rate. It is also affected by
evaporation and wind scouring. The
global sea level has risen by 20 cm
since 1970.
http://www.climate.org/topics/sea-level/
Melting Ice caps and Glaciers
Ice caps and Glaciers melt during the summer each year and during
the winter the snow which forms from sea water is usually enough to
balance the melting and maintain the sea level constant however
higher temperatures cause by global warming have increased the
average melting of the glaciers and ice caps and decreasing the
amount of snow during the winter causing an imbalance and as a
consequence of that the sea level begins to rise. 60% of the
contribution to sea level rise comes from melting of icecaps and
glaciers not including those of Greenland and Iceland whose rate of
melting has increased drastically over these past few years due to
Global warming.
Water cycles between ocean, glaciers and
the atmosphere.
Image: http://en.wikipedia.org/wiki/File:Mass_balance_atmospheric_circulation.png
Antarctica and its influence on the
sea level
Antarctica holds the most ice in the whole world with 27 million Km2.
Fortunately not all of it has melted because if it did, the sea level
would rise up to 58 metres. “The Antarctic Peninsula Ice Sheet
currently contributes around 0.22 ± 0.16 mm per year of sea level
rise[11], but has the potential to raise sea levels by up to 0.24 m if all
the ice melted” (See references).
West Antarctic Area
However, not only is the Antarctic Peninsula vulnerable, the West
Antarctic Area can also have a big impact on the sea level. The main
support (bedrock) of the west antarctic area is below sea level. This
makes the land unstable as the ice discharge has a bigger increase. What
this means is that when water gets deeper more icebergs are calved.
Definition of calved: (of an iceberg or glacier) split and shed (a smaller
mass of ice).(of a mass of ice) split off from an iceberg or glacier..This
would lead to a collapse of the West Antarctic Area which would increase
the sea level significantly.
http://takvera.blogspot.mx/
2012/09/southern-oceanwarming-impact-on.html
Future Sea Level Rise
Recent studies suggest that the sea level will rise between 0.2 and
2.0 metres by 2100, although the best estimate is 0.6m, it could
swamp many cities along the US East Coast. Likewise, a complete
meltdown of Greenland and Iceland would cause a 7.0 m rise which
would be enough to submerge London.
A collapse of the West Antarctic Ice Sheet could result in a global sea
level rise of 3.3 m, which could occur within the next 500 years.
Impacts of Future Sea Level Rises:
If greenhouse gas concentrations were stabilized today,sea level would
nonetheless continue to rise for hundreds of years. Sea level rise
threatens low lying areas around the world. Island nations, such as the
Maldives and Comoros, are particularly at risk. Coastal cities, such as
New York City and Mumbai, India must also prepare for higher sea levels.
Hurricanes and other storms are likely to become stronger. Some diseases
will spread, such as malaria carried by mosquitoes. Less fresh water will
be available. If the Quelccaya ice cap in Peru continues to melt at its
current rate, it will be gone by 2100, leaving thousands of people who rely
on it for drinking water and electricity without a source of either.
How does the sea level rising
affect us?
The sea level rising increases the chances of coastal and low lying
regions suffering from flooding and storms, which can cause the
people living in that area to abandon their homes and move to a safer
place, as one possibility is that the area is completely submerged,
this can also happen to small islands.Coastal areas will be greatly
affected by sea level rise; Tourism, aquaculture, fisheries,
agriculture, forestry, recreation, and infrastructure would all be
greatly affected since some of them such as agriculture tourism and
fishery them depend on the sea, and the other such as infrastructure
and forestry could be swamped and destroyed by a rise in sea level.
How does the sea level rising
affect us?
Another way that the rise of sea level can affect us is the
contamination of groundwater by saltwater, this can cause erosion
and impeded drainage.
Moreover, the contamination of groundwater and flooding allows the
spread of diseases such as cholera and malaria within the
communities.
How does the sea level rising
affect us?
About 40% of the world’s population lives within 100 km from
coastal regions. Thus endangering millions of lives and
billions of dollars worth infrastructure and property.
Saltwater Intrusion: Rise in sea level translates to
saltwater being included in groundwater thus endangering
water supply for drinking water, irrigation, and overrunning
agricultural fields. Furthermore low-lying areas which are
gently sloping are more susceptible to water contamination.
How will the sea level rising
affect us?
Here are a few maps showing how the potential sea rise in 100-300
years would affect five coastal Us cities.
Charleston South Carolina
The atlantic coast would push several
miles inward flooding the city by 19%
The Charles River would flood
downtown Cambridge. Logan Airport
would start to disappear. Boston
Harbour begins to encroach on
downtown.
There would be a large
widespread of flooding around
the Altantic Ocean coastline.
Most of suburban Miami, and the
Miami surrounding areas are
submerged.
Almost the whole city and it’s
surrounding areas would flood.
How are ecosystems affected by sea
level rise?
Ecosystems are affected by sea level rise because habitats are
destroyed and the patterns that are usually followed are changed;
currents can change and it can have an impact on migrating species as
well as changes in temperatures can place animals in risk of
extinction or force a species to migrate to a warmer or colder area.
Sea level rise obviously changes the depth of the ocean in some areas
this can cause ecosystems to suffer as they are not used to those
depths or the sun may not reach them as well as making it hard for
photosynthesis to take place. It can also slow down the reproduction
of plankton which is a crucial part of food chains as the temperature
gets warmer.
Mangroves and Climate Change:
The mangrove ecosystem provides income from the collection
of the mollusks, crustaceans, and fish that live there.
Mangroves can adapt to sea-level rise if it occurs slowly
enough, if adequate expansion space exists, and if other
environmental conditions are met. If sea level is rising relative
to the mangrove surface, the mangroves seaward and
landward margins retreat landward, where unobstructed, as
mangrove species zones migrate inland in order to maintain
their preferred environmental conditions, such as period,
frequency and depth of inundation and salinity. Recent study
has also shown that the the rise in sea level is having a worse
effect and making survival harder for mangroves since the sea
level rise has been accelerating.
Image Courtesy: http://www.coastalwiki.org/w/images/5/5b/Fig_5.jpg
Impact on Wildlife
Sea level rise can cause the loss of habitats of fish and birds as well as
polar bears, seals and some species of penguins are at risk of
extinction for they rely on the existence of ice caps to survive. It also
affect turtle nesting beaches because habitats are lost, as well as
extreme rainfalls can flood the nests and transfer sediment to coral
reefs, sea level rise can affect sea currents which can change
migration paths. Species that depend on one another may become out
of sync. For instance plants could bloom earlier than their pollinating
insects become active, thus causing disruption in the ecosystem.
Impacts on marine ecosystems
As the sea level rises the amount of light that reaches offshore plants
such as algae is reduced and this could affect the ability of the plant
to photosynthesise. Mangroves are also affected because they need a
stable sea level for their survival however if it happens slowly enough
they might be able to adapt.
Marine migration organisms will probably be able to adapt, however a
lot of organism’s rate of successful migration will be affected.
Similarly low lying area and coastal ecosystems will flood.
Coral reefs will suffer for sea level rise can increase sedimentation
due to erosion, this can cause reduction of sunlight reaching the reef
and allowing coral to photosynthesise.
CONCLUSION
As a group and through our research, we came to
the conclusion that the sea level will rise
between 0.8 to 2.0 metres by 2100 causing
floodings in many areas throughout the world and
possibly submerging many islands, damaging
animal wildlife as well as human. This will occur
due to the increase in temperature in the
atmosphere leading to global warming,ice sheet
melting, glacial melting and thermal expansion.
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