become a bigger and bigger issue throughout the world, it’s current and future effects are becoming better understood. One of the most talked about and publicised issues is that of rising sea levels. Although this has a number of effects, none are greater than the impacts on coastlines and coastal communities around the world.
The general consensus is that we can expect a rise of between 0.8 and 2 meters by 2100, which would be enough to flood a number of cities around the world. Direr models predict the loss of the entire Greenland ice sheet, which would increase sea levels by a huge seven meters – this would submerge much of London[sc:1]. If sea levels rise as little as one meter, island nations such as the Maldives will disappear from the map. We have already seen two of the islands of Kiribati disappear, while others have been contaminated by salt water from high tides and storm surges[sc:2]. There are two main ways that global warming induces sea-level rise – the melting of ice caps and glaciers, and the thermal expansion of water.
Melting ice caps
As global air temperatures increase, the polar ice-caps are melting – as would be expected. Since most of the ice caps are above sea level, when they melt, it adds extra water to the ocean. Together, the Greenland and Antarctic ice sheets contain 75% of the world’s fresh water. If they both melted, then sea levels would rise by around 75 meters[sc:3]. The temperatures in Antarctica are so low that the Antarctic sheet is relatively safe in the near future. An increase in temperature will have little effect, as it will still be cold enough to prevent melting.
However, atmospheric temperatures near the Greenland ice sheet are a worry. Currently, temperatures are low enough to prevent widespread melting – just. However, with a small temperature increase in the future, there is the potential for widespread surface melting. This could cause huge problems, including sea-level rise of a number of meters, and could potentially begin an irreversible warming process[sc:3].
The second, albeit smaller, problem related to melting ice-caps is the breaking up of ice-sheets and the quicker movement of glaciers. As it gets warmer, icebergs begin to break off the edge of the ice-sheets more and more rapidly. Although this currently isn’t a major issue, it has the potential to become a much bigger problem in the future[sc:3].
One of the major laws of the physics, which holds true in almost every case, is that things expand when they heat up. This expansion may be hugely noticeable, or negligible, but regardless, it is there. Over the past century, the average ocean temperature has risen by around 0.6 degrees Celsius. Most of this warming has been in the surface waters[sc:4]. Thermal expansion contributes to a large proportion of sea level rise – up to 75% according to some sources. We need to reduce greenhouse gas emissions and do what we can in order to try and mitigate the effects of climate change, or else huge numbers of people throughout the world are going to suffer for years to come[sc:5].