How much would sea level rise if all the ice in the world melted?
July 07 2021
Sea level rise is one of the direct negative effects of global warming. If sea level were to rise it would have devastating consequences, flooding small islands and coastal regions along its way.
Over the 21st century, the three major causes of sea level rising have been thermal expansion, melting glaciers and the melting of ice sheets in Greenland and Antarctica.
The exact total volume of ice on Earth is still uncertain but theoretically (with the estimated values we currently have), if it all melted global sea level would rise approximately 65 meters causing major flooding on coastal cities across the globe.
For every celsius degree of temperature rise in the global climate, an estimated sea level rise of 2.3 meters would occur over the period of 2000 years. This is the conservative estimate taken into account when calculating the impact, but it could be worse if we take the most recent values of global temperature rising.
Thermal expansion comes as a consequence of ocean warming, which leads to sea water density decreasing and expanding therefore causing sea level to rise.
Decades ago, thermal expansion affected sea level rising in a major way since the Antarctic and Greenland ice sheets weren’t melting at the current rate. Ice sheet melting has increased significantly during the last years and it is now the biggest factor causing sea level to rise.
To get a better understanding of what causes mountain glaciers to melt, we must first understand how they are formed. Glaciers are formed from snow accumulation that compresses over the years and forms large masses of thick ice. They have the ability to flow like slow rivers and currently occupy 10% of the Earth’s land area, storing 70% of its freshwater.
Every passing year, snow falls on glaciers increasing their mass during the cold season, and melted water flows away from them during the warmer season. What is happening right now is that there is more meltwater than snow fall so glacier mass is decreasing.
Glacier melt has accounted for 21% of the global sea level rise during the last 20 years and has been forecasted to become the second biggest cause of global sea rising during the 21st century.
An ice sheet is a glacier mass with a dome-shape which exceeds 50,000 square kilometers. Ice sheets can be found in Greenland and Antarctica. Ice sheet mass loss now dominates sea level rise being the major cause for its acceleration.
The Greenland ice sheet and the West Antarctic ice sheet are especially vulnerable because most of their mass sits on bedrock below sea level. The floating ice sheets are collapsing as the warming ocean is melting them from below, making them potentially unstable. If they were to rapidly collapse, sea levels would rise at a rate not seen since the paleo era.
Ending climate change
In an attempt to put an end to climate change, a legally binding international tractate was adopted by 196 Parties at COP 21 in Paris, on 12 December 2015. This tractate was named The Paris Agreement and it came into force on November 4th, 2016.
The main goal is to limit global warming to below 2 degrees celsius. To reach this goal, countries aim at reducing greenhouse gas emissions and reducing the global climate temperature by mid-century.
The constant burning of fossil fuels is one of the factors that affects the high level of gas emissions and, in consequence, global warming. There is a sense of urge to reduce these greenhouse gas emissions because if we continue adding carbon to the atmosphere at the current rate, we could see the worst effects of global warming sooner than later.
- National Geographic - What the world would look like if all the ice melted, https://www.nationalgeographic.com/magazine/article/rising-seas-ice-melt-new-shoreline-maps, visited 27/06/21.
- Carbon Brief - Melting glaciers drove ‘21% of sea level rise’ over past two decades, https://www.carbonbrief.org/melting-glaciers-drove-21-of-sea-level-rise-over-past-two-decades, 28/04/2021.
- Carbon Brief - Explainer: How climate change is accelerating sea level rise - https://www.carbonbrief.org/explainer-how-climate-change-is-accelerating-sea-level-rise, 23/09/2019.
- Hugonnet, R., McNabb, R., Berthier, E. et al. Accelerated global glacier mass loss in the early twenty-first century. Nature 592, 726–731 (2021). https://doi.org/10.1038/s41586-021-03436-z
- Slater, T., Lawrence, I. R., Otosaka, I. N., Shepherd, A., Gourmelen, N., Jakob, L., Tepes, P., Gilbert, L., and Nienow, P.: Review article: Earth's ice imbalance, The Cryosphere, 15, 233–246, https://doi.org/10.5194/tc-15-233-2021, 2021.
- U.S. Global Change Research Program - Sea Level Rise, https://science2017.globalchange.gov/chapter/12/, visited 26/06/21.
- NASA - NASA-led study reveals the causes of sea level rise since 1900, https://climate.nasa.gov/news/3012/nasa-led-study-reveals-the-causes-of-sea-level-rise-since-1900, 21/08/2020.