Melting Ice - Larsen B

In my last post, I introduced melting sea ice as one of the major changes occurring to our planet, and one that is certainly affecting Antarctica at the moment. Today I’m going to discuss the melting ice in more depth.

Over the past 200 years or so, the human footprint on the world has become so apparent and so profound that we humans now ‘rival the great forces of Nature and are pushing Earth to a new planetary terra incognita’ (Steffan et al. 2007: 614). This has created to need for a new epoch away from the Holocene to one that is more reflective of human actions. “The Anthropocene” was termed to capture this. Although there is much debate about the precise time that this epoch started, e.g. at the start of the Industrial Revolution, or a few hundred years earlier (Zalasiewics, et al. 2011; Crutzen and Stoermer, 2000; Gale and Hoare, 2012), this epoch signifies that because of humans, Earth is becoming warmer, less biologically diverse, less forested, wetter and stormier (Steffan et al. 2007). The emission of greenhouse gases, like carbon dioxide and methane, into the atmosphere is creating a warming effect, i.e. the greenhouse effect, whereby the Earth will warm by 1.4 to 5.8^oC by the end of the century (Crutzen, 2002). I came across a very insightful TEDx talk in which Steffan Will goes into more depth explaining the origins of the Anthropocene which can be view here if my readers wish to learn more. 

Unsurprisingly, a warmer planet is troublesome for ice. Below is a graphic representation of Antarctica, displaying the continent's ice shelves and glaciers.

Figure 1. Source: Adapted from Rignot and Stanley (2002)

According to Pritchard et al. (2009), some glaciers are thinning at alarming rates. For example, Pine Island glacier is thinning by up to 18 feet per year, while the Smith glacier is thinning by 27 feet per year. This highlights the severity of warming occurring today. Glaciers in Antarctica are at risk of becoming less stable as the planet warms.

The circled ice shelf in Figure 1 is the Larsen B ice shelf. In 2002, it collapsed and fell apart. Cited by Schmidt (2011), this was predicted by Mercer (1968), who wrote that global warming caused by industrial pollution would lead to a collapse West Antarctica’s ice shelves. Figure 1 shows the levels of carbon dioxide emissions from 1850 onwards. The figure agrees with Mercer, showing that emissions have risen due to industrialisation. I have also included a diagrammatic representation of the change in global temperatures, shown in figure 3. Figures 2 and 3 are complementary in that they demonstrate the correlation between carbon dioxide emissions and global temperature rises

Figure 2: Total global carbon dioxide emissions from fossil fuel combustion initiated by industrialisation.
Source: Hardy (2003) 'Climate Change: Causes, Effects and Solutions', p. 13.

Figure 3: Variations in Earth's temperature for (a) the past 1,000 years and (b) the past 140 years, gathered from proxy measurements based on tree rings, corals, ice cores and historical records. Source: Hardy (2003) 'Climate Change: Causes, Effects and Solutions', p. 41.

A recent study by Rebesco et al. (2014) showed that the Larsen B ice shelf collapsed because of warmer air, partly by human activities and our effects on warming the planet. Their results show that the Larsen B ice shelf shattered in the following way:

• Warmer temperatures warmed up the air
• Warmer air melted ice during the summer months
• This water flowed into cracks inside the ice shelf
• As winter approached, all the water froze again and expanded in the cracks
• This caused the ice shelf to shatter from the increased pressure in the cracks

Below is a very short video capturing the Larsen B ice shelf collapse from satellite images in 2002, illustrating what happened visually. Unfortunately I can't post the actual video on the blog. 

https://www.youtube.com/watch?v=N61EP5zB8uU#t=28

To summarise this post, I’ve presented the view that the Larsen B ice shelf collapse was partly caused by humans because of human induced warmer air in Antarctica. The score for negative human impacts verses positive/ natural impacts is 1-0. In my next post, I will present some of the criticisms of the views presented in this post.