The cold environments questions/sample answers in the 2021 AQA Assessment materials

These are to balance the coastal questions and answers published a few days ago...

1. Explain the formation of roches moutonnees.  (4)

Rôches moutonnées are erosional landforms found in previously glaciated valleys. More resistant protrusions of rock are eroded smoothed and shaped by an advancing glacier.  The rôche moutonnée is smoothed and eroded in the direction that the glacier that once passed over it. This is referred to as the stoss side. This is often marked with glacial striations which are aligned to the direction of ice travel. The rough and craggy down-ice (leeward) side is formed by plucking or quarrying. This erosional process is initiated when ice melts slightly by pressure and seeps into cracks in the rock. When the water refreezes, the rock becomes attached to the glacier, but as the glacier continues its forward progress it subjects the stone to frost shattering, ripping pieces away from the rock formation.

Figure 7 shows the mean mass balance and cumulative mass balance for selected glaciers around the world. Analyse the data shown in Figure 7. (6)

It is clear that the cumulative mass balance of glaciers around the world has been negative since around 1970 – in other words the size of glaciers has lessened with ablation being higher than accumulation. Only prior to this date was it positive. The rate of decrease has increased in the last few decades and so the cumulative loss is now more than 20,000 mm w.e. This is also shown for the mean mass balance for the selected glaciers, although this decline has had more fluctuations. For these selected glaciers, the mass balance actually became positive for a couple of years in the 1980s. There were also some years of growth in the generally negative trend, for example in 2001 and 2010.

Finally, it is curious that the number of glaciers selected for the ‘selected’ category has not been consistent, though for most of the time it was about 40 in number. The figure was much less before 1967 and interestingly more recently, at about 25 in 2016. This lack of consistency may make this aspect of the data less useful.

Figure 8 shows an area of tundra vegetation in the Sajama National Park, Bolivia. Using Figure 8 and your own knowledge, assess the view that temperature variation is the most significant factor in the development of this vegetation. (6)

The photo shows an area of tundra vegetation with a prevalence of low and small shrubs separated by areas of bare ground. There are no trees evident. The photo also shows potential temperature variations with a snow-covered mountain in the background, and a slope with sunshine on it in the foreground.

It is likely that the area will have very low temperatures in winter, below freezing point, which will last for several months creating a short growing season. The low temperatures and short growing season will create the sparse vegetation as shown, so there will be a lack of nutrient material in the soil, and hence little encouragement of a denser vegetation cover – a form of positive feedback. Furthermore, the cold temperatures limit bacterial activity, especially where there is permafrost, making the soil less fertile. During the short warmer summer season, flowering plants such as anemones and saxifrages will burst into life producing a mass of colour to take advantage of the suitable conditions.

Although precipitation levels are low, often of snow in winter, it is true that temperature variations are the most significant factor in the development of this form of vegetation as the growing season is so short.

‘Warming taking place in fragile cold environments is set to generate unprecedented impacts affecting both people and the physical environment.’  To what extent do you agree with this view?

As climate change has taken place, scientists have already measured a retreat in the permafrost zone. This is particularly acute in northwestern Canada and in Siberia, for example, increases in temperature of only 1oC have led to the trebling of the thaw rate in parts of central Canada. It is clear that these changes are set to generate unprecedented impacts affecting both people and the physical environment.

The immediate impacts of melting can be seen in Arctic communities – buildings have become undermined, roads subside unevenly and crack, and the supports holding utility pipelines can shift and even crack them. Modern buildings are often now insulated or raised above the ground with piles driven into the permafrost to avoid the ground warming up and developing thermokarst. Utilidors are used, which are insulated boxes, elevated above the ground, which carry water supplies, heating pipes and sewerage between and from buildings, and are designed not to melt the permafrost. These are potentially new and significant impacts on people’s lives.

Given the world’s dependence on oil and gas, the threat of pipelines having to be shut down is alarming. Alaska has vast reserves of oil and gas. They were first discovered around Prudhoe Bay in the north, which was inaccessible to ships due to pack ice. A pipeline needed to be built to the ice-free port of Valdez on the south coast of Alaska. This was constructed on insulated legs to avoid the warmed oil (warmed, so that the oil does not freeze in such low temperatures) from melting the permafrost and causing the pipeline to sink and break. It also zigzags to avoid rupturing by ground movement due to either frost heave or earthquakes. Any breakage would damage the physical environment.

Another major, and certainly unprecedented, concern regarding the melting of permafrost is the release of organic carbon. The soils of the permafrost are normally crammed with un-degraded, well-preserved organic matter in the form of leaves, twigs, roots etc. This is an enormous store of carbon, kept inert by being frozen in the ground. However, if the ground was to melt and the organic matter start to rot, carbon would be released as either carbon dioxide or methane, creating more greenhouse gases. This will melt more permafrost, in a worsening positive feedback cycle. The Arctic is estimated to contain about 900Gt of carbon. Humans emit about 9Gt of carbon from fossil fuels and deforestation every year. Hence, it would only take the release of 1% of carbon in Arctic permafrost soils to effectively double our emissions of greenhouse gases, especially methane. Although permafrost may seem an irrelevance to those of us in the temperate latitudes, it is clear that changes in it may have significant and unprecedented consequential effects on our lives through its impact of greenhouse gases.

So, this warming of fragile cold environments presents a number of challenges. Firstly, the sheer size of the land areas involved across the ‘top’ of the world – northern Canada and Alaska, together with northern Asia – means governance will be difficult. The range of governments involved and the differing political principles of those governments, e.g. the USA and Russia, for example, will make it difficult to come to a consensus. Finally, there are practicalities and costs of bringing so many different people together – where, how, and even what language in which to communicate. But, unless something is done, the warming of the fragile cold environments in the northern hemisphere will generate unprecedented impacts for both people and the physical environment.