Q1. What is the role of Arctic sea ice in the global climate?
A. Sea ice plays a major role in the Earth’s energy balance, and therefore the global climate. Sea ice surfaces have a high albedo, meaning they reflect a large proportion of incoming solar radiation that reaches the Earth’s surface. Compared with the open ocean, sea ice albedo is over 12 times greater, and therefore whilst much of the Earth’s incoming energy (heat) is absorbed by the ocean, sea ice has the ability to keep the planet cool.
Due to differences in albedo, as an average across the Arctic, there is an estimated 25 W/m2 (Watt per square metre) reduction in solar radiation absorption by sea ice in comparison to the open ocean. When scaled to the full Arctic sea ice area, the reduction in energy absorption over a year from sea ice corresponds to about one third of the Earth’s total energy imbalance as of the early 2020s (the excess between incoming solar radiation and reflected solar radiation).
Calculations[1] have found, using reasonable assumptions, that extending sea ice life by 1 month into the summer over a period of 20 years is comparable to removing 1000 tCO2 (tonnes of carbon dioxide) per square kilometre of ice. The same calculations also estimated that 30-75cm of additional sea ice is needed to delay summer melt by 1 month, which is a key motivation for our research.
In addition to planetary cooling, Arctic sea ice also plays an important role in global ocean circulation, which distributes heat around the planet, as well as in mid-latitude weather patterns through its indirect links to the jet stream and storm tracks.
[1] Calculations performed by Laura van Djike and Real Ice, using the absolute global warming potential (AGWP).[2]
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[2] Jussi Lintunen, Aapo Rautiainen. On physical and social-cost-based CO2 equivalents for transient albedo-induced forcing, Ecological Economics, Volume 190. 2021. DOI https://doi.org/10.1016/j.ecolecon.2021.107204.
Q2. What are the local impacts of Arctic sea ice loss?
A. For some Arctic communities, such as the Inuit of Canada, Alaska and Greenland, sea ice is fundamental to their traditional way of life. Populations of ecologically and culturally significant species such as caribou, seals and walrus are tightly linked to the presence of sea ice habitat, and declines in biodiversity impact the availability of Inuit sources of food, clothing and tools.
Loss of sea ice also poses challenges to the safe passage of hunters to hunting grounds, and has contributed directly to loss of life. In addition, Inuit populations have faced rises in poverty, isolation, food insecurity and poor health, as well as loss of traditional community practices due to struggles to maintain their traditional ice-dependent ways of living.
The loss of sea ice and transition to more extended open ocean seasons has also been linked to greater coastal erosion across the Arctic, which affects coastal communities due to rapid land loss.