Assignment #2

Physical Oceanography

KL2205

Ahmad Muklis Firdaus, ST.MT.

Shafira Anindita

15512049

Ocean Engineering Department

Faculty of Civil and Environmental Engineering

Bandung Institute of Technology

2014

What is global warming? Global warming is basically a rising of earth’s average

temperature due to the effect of heat-trapping gas, or more commonly known as

greenhouse effect. This phenomenon’s effects include extreme weather events, radiative

forcing, oxygen depletion, and warmer temperature of ocean. The rising temperature of

even a two to six degree of the ocean would lead to significant effects, including the

melting of glaciers and icebergs in Arctic sea and loss of freshwater storage in

Himalayan glaciers. And all these events would cause a big long-term effect: sea level

rise.

Sea levels worldwide are indicated to have been rising at rate of 3.5 millimeters

each year. This phenomenon is induced by numbers of main factors, they are melting of

thermal expansion, and ice loss from Greenland and West Antartica, and glaciers and

icebergs 1 .

Latest scientific research indicates that icebergs in Arctic sea melt faster than ever

and the North Atlantic seawater has already become fresher over the past times. As the

global warming occurs, the precipitation in North Atlantic increases, plus the ice in

Arctic sea continues to melt, then the freshwater from the melting ice flows out over the

ocean at mid and high latitudes, and making the seawater at those areas less salty and

hence less dense, and this what makes the North Atlantic sea water fresher than

previously2. This less salty and less dense seawater won’t be able to sinks and circulates

the deep ocean as it’s supposed to be, and this leads to anomaly of thermohaline

circulation or more well-known as the ocean conveyor belt circulation.

Thermohaline circulation is a large-scale constant water movement or circulation

in ocean. This motion is caused by surfaced heat and freshwater flows. Thermo derives

from temperature, and haline derives from salinity. Cold and high saline water sinks to

the bottom part of the ocean, and warmer and less saline water rises to surface. The

warmer water heats the atmosphere in the northern latitudes, and then it gets cooler and

less dense and sink, then it flows south down all the way to the Antartica, and eventually

the cold water is able to get warm again and continue the circulation3.

The ocean conveyor belt circulation is supposed to move warmer water in the

surface from southern hemisphere toward the North Pole. This carries a great heat

toward the north from the south, and this plays a big role in maintaining the climate. As

                                                                                                               1  Source:  http://ocean.nationalgeographic.com/ocean/critical-­‐issues-­‐sea-­‐level-­‐rise/  2  https://spark.ucar.edu/longcontent/melting-­‐arctic-­‐sea-­‐ice-­‐and-­‐ocean-­‐circulation  3  http://oceanservice.noaa.gov/facts/conveyor.html  

we can see from above, these are linked one another. If the global warming occurs,

Arctic sea continues to melt, the salinity and density of the water in the surface reduce,

the ocean conveyor belt circulation will slowly be disrupted, and eventually leads to the

climate interference. If the circulation stops, the heat in the southern hemisphere will not

be carried northward, and this will cause the southern hemisphere to get warmer, and the

northern hemisphere to get colder by 5o to 10o Celcius. Geographically, the eastern

North America and the western Europe will experience a significant climate shift.

Other than that, the impact of global warming to the ocean is a warmer ocean. It is

true that the report says ocean temperature is a better indicator of global warming than

the air temperature4. By the global warming occurring, the atmosphere stores less

percentage capacity of heat, the surface of earth absorbs heat slowly because it is a poor

conductor, and thus, ocean absorbs the heat for almost all of the earth’s radiative

imbalance. These abnormal changing of temperature of the ocean does not only affect

the thermohaline current but also causes a big changes to the marine food chain. As the

ocean temperature rises, zooplanktons tend to overgrow the phytoplanktons which

suppose to suck up carbon dioxide.

                                                                                                               4  http://www.theage.com.au/environment/rising-­‐ocean-­‐temperatures-­‐near-­‐worstcase-­‐predictions-­‐20090619-­‐cmcs.html