c) It has been suggested that global warming will result in rising sea level, as polar regions warm and polar ice melts. This has been questioned, since some assert that warming the poles will result in more snow, thus more accumulation of ice, and not melting. There is, however, one impact of warming that can be easily evaluated arithmetically, and that is the impact on sea level resulting from warming the water.

The coefficient of thermal expansion of seawater is approximately 0.00019 per degree Celsius. This simply means that, given a volume of seawater, that volume will expand by this fraction as a result of heating the water, per degree. Now since ocean basins are constrained by their bottoms and "sides", the only way to go is up. Note that this also could result in extensive coastal flooding.

To calculate how much a temperature increase would increase sea level, simply multiply the average ocean depth in cm by the coefficient of thermal expansion (c.t.e.) by the number of degrees of temperature rise. (Note that we put a 1 before the c.t.e. value to obtain the height of sea level after the warming. If you simply multiply the average depth by the c.t.e. you will get the number of centimeters that sea level will rise.) With this understood, how much would each 1 oC increase in seawater temperature cause sea level to rise? Express your answer in cm. (30 cm = 1 ft). Recall the average depth is 3,800 m (3.8 km).

Answer

To answer this question we have to remember again the assumption that was discussed in Question 1b, namely that water added to the volume of the ocean basin or increased volume due (in this case) to thermal expansion will go up, and the lateral movement will be negligable. Again you should ask yourself is this a reasonable assumption? Making this assumption the procedure for calculating volume increase for each 1oC increase in seawater temperature is outlined above. Using that example we would calculate the sea level rise as follows:

Average Ocean depth = 3.8 km = 3,800 m = 3.8 * 105 cm

3.8 * 105 cm * 1.00019 = 3.800722 * 105 cm

or 72.2 cm