Welcome to the return of Understanding climate change – a series detailing what I’ve learnt through the ‘Climate Change: Challenges & Solutions’ online course. The course may have finished a while ago now, but it never too late to learn something new. Have a look back at the previous entries if you missed them last time:
Impacts on Natural Systems
The response of ice sheets to a warming climate is the subject of many a scientific study. Antarctica and Greenland are the focal points, given that 99% of the glacier ice on Earth is found in these ice sheets.
Greenland in particular has shown a very rapid response to warming over the past two decades. The loss of mass is due to melting of ice on the surface, and the breaking off of ice chunks at the edges (known as calving).
In the summer months, about half of the surface of the ice sheet naturally melts. However, in the summer of 2012 the degree of ice melt was above normal for nearly the entire season, leading to a 97% melt extent and lasting two months longer than average.
The increase in flow of ice causes spreading of the ice sheet. As this occurs, the proportion of the ice at the edges increases and more is lost through calving. Furthermore, melted ice that flows down through the ice sheet reaches the bed, which can then have a lubricating effect on the ice sheet flow.
What is important, is that the loss of floating ice does not contribute to sea level rise, since it would already have displaced its mass in the water. Of course, ice melt and calving are natural mechanisms and the presence of these events does not necessarily equal a mass reduction for the ice sheet. Neither are individual calving events, like the one below, evidence of climate change.
Increasing carbon dioxide levels affect ocean systems as well, with acidification being a major threat to biodiversity. There are at least a quarter of a million different species living in the ocean, but considering that it represents 99% of the living space for animals, there are likely a lot more that have not yet been discovered.
This video details the chemistry behind ocean acidification.
Since the industrial revolution, the pH of the ocean has fallen by about 0.1 – equivalent to a 30% increase in the concentration of hydrogen ions. The rate at which acidification is happening is causing problems for many marine species – particularly marine invertebrates with calcium carbonate shells.
Not only is a more acidic ocean likely to dissolve those shells, it also makes them more difficult to form. There are other problems for species where fertilisation of sex cells happens externally, since these cells are extremely sensitive to environmental conditions. Marine invertebrate larvae also have this problem.
NASA has loads more information on their website if you want to check it out.