the spatial extent of the cryosphere (see Chapter 2).
Thus, while changes in sea ice and snow cover can be considered as impacts of climate change, the role of these changes in the albedo-temperature feedback also makes them agents of change, through a positive feedback loop (see Figure 1.13). As temperature increases, surfaces with low albedo powers (ice-free ocean and land surface devoid of glaciers and snow) increase and absorb more solar radiation and become warmer.
Figure 1.13. Positive feedback loops explaining the amplification of Arctic climate warming
(source: design D. Mercier, drawing by F. Bonnaud, Faculty of Arts, Sorbonne University, 2020). For a color version of this figure, see www.iste.co.uk/mercier/climate.zip
In addition to albedo, Figure 1.12 illustrates the major components of the Earth's radiation budget, which is simplified by an average solar energy input of 342 watts per square meter to the Earth's surface. The percentages of each component (clouds, ocean, land surface, atmosphere) show that only 47% is absorbed (25% by the oceans and 22% by land surfaces). In the evolution of temperature in the lower layers of the atmosphere, the cloud component plays a fundamental role because it absorbs part of the energy (19%) and reflects 20%. Cloud cover and its temporal evolution therefore appear to be an essential element in understanding the evolution of the radiation balance on the Earth's surface.
1.6. Conclusion
Contemporary climate change is illustrated by recognized and measured thermal and rainfall trends that are neither linear over time nor spatially uniform. Beyond the general logics of the physical laws governing the climate machine on a global scale (radiation balance, importance of astronomical parameters, role of greenhouse gases and volcanism, thermal gradients, air humidity capacity, etc.), regional and local nuances illustrate the importance of geographical factors and interactions between all components, such as the fundamental Arctic-wide interaction between the ocean, sea ice and the atmosphere. Whether during the cold Pleistocene sequences or during contemporary global warming, we are seeing an amplification of changes in high-latitude environments, particularly in the Arctic Basin.
1.7. References
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Bourriquen, M., Mercier, D., Baltzer, A., Fournier, J., Costa, S., Roussel, E. (2018). Paraglacial coasts responses to glacier retreat and associated shifts in river floodplains over decadal timescales (1966-2016), Kongsfjorden, Svalbard. Land Degradation and Development, 29(11), 4173-4185.
Cheng, L., Abraham, J., Zhu, J., Trenberth, K.E., Fasullo, J., Boyer, T., Locarnini, R., Zhang, B., Yu, F., Wan, L., Chen, X., Song, X., Liu, Y., Mann, M.E. (2020). Record-setting ocean warmth continued in 2019. Advances in Atmospheric Sciences, 37, 137-142.
Forland, E.J., Benestad, R., Hanssen-Bauer, I., Haugen, J.E., Skaugen, T.E. (2012). Temperature and precipitation development at Svalbard 1900-2100. Advances in Meteorology, 2011(17).
Hanssen-Bauer, I., Forland, E.J., Hisdal, H., Mayer, S., Sand0, A.B., Sorteberg, A. (2019). Climate in Svalbard 2100 - A knowledge base for climate adaptation
Humlum, O., Solheim, J.-E., Stordahl, K. (2011). Spectral analysis of the Svalbard temperature record 1912-2010. Advances in Meteorology, 2011.
IPCC (2014). Climate Change 2014: Synthesis report. Contribution of working groups I, II and III to the fifth assessment report of the Intergovernmental Panel on Climate Change. Report, IPCC, Geneva.
IPCC (2019). Special report on the ocean and cryosphere in a changing climate. [Online]. Available at: https://www.ipcc.ch/srocc.
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Lageat, Y. (2019). Les variations du niveau des mers. Presses Universitaires de Bordeaux, Pessac.
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1 1 https://public.wmo.int.fr.
2 2 Zetta: one trilliard (1021) or one thousand trillion, according to the international system of units.
3 3 http://www.climate4you.com/SvalbardTemperatureSince1912.htm.
4 4 Representative Concentration Pathway (RCP), scenario expressed in watts per square meter.
2
Climate Change and the Melting Cryosphere
Denis Mercier
Sorbonne University, Paris, France
2.1. Introduction
Contemporary climate change affects the cryosphere; the thermal changes at stake today are limited compared to the great climatic oscillations that affected the Earth, particularly during the past 2.58 million years of the Quaternary Period. Indeed, the areas concerned, and the volumes of ice are undeniably not of the same order of magnitude. During the great cold periods of the Pleistocene (2,580,000 to
