Global sea level rise is attributed to a few causes, mainly
thermal expansion and melting of ice. These two factors lead back to the
phenomenon of global warming, which we know is mainly resulted from the release
of heat-trapping greenhouse gases into the atmosphere. It has also become clear
to us that this warming is predominantly human-induced in this day and age,
escalating greatly after reign of the Industrial Revolution.
Explaining the context of thermal expansion would take us
back to one of the basic properties of matter – that it expands when heated.
The warming of the ocean has caused seawater to occupy a greater amount of
volume and hence space. The melting of land ice, which comprises of glaciers
and ice sheets contribute a much greater proportion towards sea level rise
compared to ice caps from sea ice. However, the melting of sea ice in areas
such as Greenland and the Antarctica indirectly affect sea levels. Land ice
that has extended out onto the coast of the particular landmass is termed as ice
shelves. The melting of these ice shelves could then potentially cause glaciers
and ice sheets to lose its grip on the land surface and get displaced into the
sea, hence increasing the volume of the sea.
The main implication of sea level rise is the increase of
storms and flooding. As the sea level continues to increase, water moves more
inland, thus increasing the likelihood of more and more people being affected
by this occurrence. Flooding, the mildest possible phenomenon may simply pass
off as an inconvenience to many. However, taken towards the greater end of the
spectrum, people’s homes or even lives could be in jeopardy because of this. Past
records of hurricanes and heavier flooding show us how detrimental the effects
can get.
The areas across the globe where these effects are severe
are usually low in altitude, with coastlines tending to be more susceptible. Some
examples that are most spoken about are areas such as the east coast of the
United States, small islands such as the Maldives, and certain developing
countries like Bangladesh. Several factors come into play when taking into
consideration these more susceptible areas, the dominant factor being altitude.
The rates of sea level rise also vary in different parts of the globe. In
addition to that, the geology of a certain area plays a role in this, with its
tectonic activity determining the nature of its coastline. Alaska
has proven to be a good example of a country where there are variations in sea
level change.
Aside from humans, other living beings as well as plants
will be affected. Aside from flooding, intrusion of salt water can upset a
certain habitat that is not used to salt water, like freshwater swamps and
marshes. The influx of salt can alter the chemistry of the soil in that area,
and this could cause several plants and other organisms to perish.
How quickly is the sea level rising? Several studies have
been carried out to model sea level rise to aid future projections, taking into
account the factors that come into play. Levermann et al. state
that thermal expansion contributes about 0.4m/°C while the melting of the
Antarctic ice sheet contributes approximately 1.2m/°C. After taking into
consideration the Greenland ice sheet, the sea level may rise at a rate of
about 2.3m/°C. The Intergovernmental Panel on Climate Change (IPCC) estimated a
range of a 28-98cm rise in sea level by the year 2100. Church and
White state that from January 1870 to December 2004, there was acceleration
in sea level rise of about 0.013±0.006mm/yr2 and that sea level
would rise by about 28-34cm by 2100 if this acceleration stayed the same.
Essentially, previous studies to project and predict sea
level change aim to give us the best approximation of what will happen in the
future. Even if serious measures to reduce anthropogenic (human-caused) impacts
on the environment, sea level could continue to increase, displaying an inertia
towards the implications of this environmental change. The best way to put this
issue into context would be to look at some individual case studies on sea
level rise to see how it impacts humans and other living organisms on a smaller
scale.
Here is a link to an article that provides information on sea-level
rise in a very understandable manner:
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