Faculty of Engineering, Environment and Computing Geosystems
Activity Brief 3: Climate Review
Review the scientific argument for climate change and the influence of both natural and anthropogenic forcing agents in this process
Portfolio Task 3 – Climate Review
A. Background
Climate change predictions suggest that global sea levels will rise, but uncertainty remains regarding the magnitude of the increase. Providing a specific prediction for sea level rise for the end of the current century (AD 2100) is a difficult task, and often relies on intensive numerical modelling experiments that are beyond our ability to perform in this module. However, we can evaluate how much sea level rise is POSSIBLE, based on our understanding of the different sources and mechanisms of sea level rise.
In this assignment, you will calculate the potential sea level rise from various sources, critically review this in comparison to the Intergovernmental Panel on Climate Change (IPCC)’s sea level projection for 2100, and use your findings in combination with published literature to suggest, and justify, what you believe to be a reasonable projection for sea level rise by 2100.
B. Preparation
Thermal Expansion
The first mechanism to consider is thermal expansion of the seawater itself. All materials expand when they heat up, and water is no different. Although we are talking about a volume change, the ocean will have to expand laterally (by flooding land) as it rises, which poses a complicated problem! For simplicity, we will consider the expansion to be a linear rise in the surface of the ocean:
(Equation 1)where
ΔH is the change in height of the ocean,
H is the coefficient of thermal expansion of seawater (6.9 x 10-5 oC-1),
ΔT is the temperature change and
H is the average depth of water in the ocean (we will assume 5000 m).
For this assessment, answer:
Question 1: Calculate how much sea level will rise by due to thermal expansion, assuming a 2oC temperature rise from global warming.
Ice Sheets
The second major way of causing sea levels to rise is by putting more water into the oceans. The biggest reservoirs of freshwater are those locked up in ice sheets. You can assume that 361 km3 of ice or snow is the equivalent of 1 mm of sea level change. Using this value, estimate the amount of sea level change that would occur if the snow / ice masses in Table 1 melted completely. Note the different units used for different measurements in the table!
Table 1. Ice and Snow Calculations.
| Ice / Snow mass | Area (106 km2) | Average Thickness (m) | Volume (km3) | Sea Level Equivalent (mm) |
| All Snow | – | – | 50,000 | |
| All Mountain Glaciers | 0.54 | 241 | ||
| Greenland Ice Sheet | 0.996 | 1706 | ||
| West Antarctic Ice Sheet | 1.2 | 1800 | ||
| East Antarctic Ice Sheet | 11.2 | 2010 |
Now that you have completed your calculations, for this assessment, answer:
Question 2. Which reservoir of freshwater is the largest potential contributor to global sea level rise?
Question 3. Assuming no thermal expansion of the oceans, what is the LARGEST sea level change that is possible?
Question 4. What is the LARGEST possible sea level change with the inclusion of thermal expansion?
