With increasing global temperatures, one of the most consequential effects is a rise in sea levels. Rising seas erode coastlines and submerge islands, drastically impacting settlements, ecosystems and natural resources. An understanding of what causes sea level rise, and how to adapt to or prevent it, is critical to our survival as a species.
At its core, global warming causes the world’s oceans to expand as the water warms. As the air gets warmer, the ocean absorbs most of its heat. According to a report by the United Nations Intergovernmental Panel on Climate Change, since 1992 about 93% of the energy produced by the increased global temperatures has been absorbed by the world’s oceans. This heat causes the water to expand, which leads to an increase in sea levels.
Additionally, melting glacier ice contributes to rising sea levels. Glaciers in the Arctic and on mountain ranges around the world are shrinking due to rising temperatures. This has caused an increase in the volume of water in oceans, threatening coastal communities and fragile ecosystems. One of the cases where this can be seen more clearly is in the Antarctic, where Antarctic ice sheet sea level rise is one of the most worrying aspects of global warming and, in total, contributes between 30 to 60 percent of all global sea level rise.
Furthermore, when an ice sheet melts it slides more quickly into the sea, increasing the average rate of sea level rise. For example, in 2019, for the first time ever, scientists documented Greenland’s vast ice sheet melting at an accelerated rate. In the same year, a report from the Intergovernmental Panel on Climate Change stated that glaciers and ice caps are shrinking in all continents, except Antarctica. This means less of their water is absorbed into the ground or ends up in rivers but, instead, ends up in oceans, contributing to higher sea levels.
Sea levels also increase when water from landmasses is transferred to oceans. This usually occurs when large-scale human activities, such as deforestation and intensive agriculture, disrupt surface runoff. When the surface runoff retains more water and takes longer to penetrate into soils and subsoil, more is accumulated, transferring more water downstream to the oceans. In addition, coastal development, such as building dams, steel piers and roads on marshes and tidal flats, reduce their sponge-like capacity to absorb water and cause them to become shallower and eventually dry up, resulting in less water absorption directly into the ground and, consequently, into the oceans.
Considering the implications of rising sea levels, it is incumbent on governments, civil society and the private sector to act swiftly and use a variety of policy tools to tackle global warming and, by extension, the ramifications it has on sea levels. Keeping global temperatures in check and transitioning to green energy sources are all essential, but equally important are the efforts to protect and restore coastlines, wetlands and other shorelines, reclaiming land while strengthening the natural infrastructure that absorbs water, preventing it from pouring into the oceans.
To sum up, the rise in sea levels due to global warming is an alarming effect that threatens the environment, ecosystems, coastal and maritime safety and, ultimately, human livelihoods. We must act now and work across borders to prioritize the sustainability of our planet for future generations.
