Rising Sea Levels: A Crash Course for Everyone
Jacqueline Austermann is an assistant professor at Columbia University and a member of the Division of Seismology, Geology and Tectonic Physics at the Lamont-Doherty Earth Observatory at the Columbia Climate Institute. Her most recent presentation has focused on what is driving sea level rise, and why sea levels can be different in different locations.
this The latest and most complete The report of the Intergovernmental Panel on Climate Change (IPCC) has dire warnings. The report details how humans are responsible for the 1.1°C rise in temperature since the industrial age. It also shows that the effects of this warming are already deadly and disproportionately harming the world’s most vulnerable populations. But there is also hope. The report concludes that it is still possible to prevent the worst effects of global warming, but doing so will require global cooperation, billions of dollars and profound societal change.
So high stakes, a lecture at Columbia Climate Schoolof Lamont-Doherty Earth Observatory, “How Much Will Sea Levels Rise? Insights into the Past to Forecast Future Change,” drew near-full-house crowds last week.assistant professor Jacqueline OstermanAffiliates of the Lamont Division of Seismology, Geology and Structural Physics delivered presentations.
“[Jacky] “He’s a very well-known young scientist,” said Maureen Raymo, director of Lamont and co-president of the Columbia Climate Institute, who introduced the lecture. “Last year, she was named a worthy scientist by Science News.” One of 10 scientists to follow. She is the 2021-2023 recipient of a Sloan Research Fellowship, a prestigious fellowship awarded to scientists. “
Osterman frames the conversation by first describing the stakes—how sea levels threaten global infrastructure, and the homes and livelihoods of millions of people. Then she started researching the evidence.
“If we look [the rate of sea level rise from] From 1900 to 1990, we saw sea levels rise by about half an inch per decade, or a little over a millimeter per year. Over the past few decades, this has been accelerating to three to three and a half millimeters per year,” says Austermann, pointing to and describing various measurement techniques.
A slide from Osterman’s presentation shows the rate at which sea levels have risen in recent decades.
Austermann explained that sea-level rise is the result of three dynamics: about one-third of sea-level rise comes from thermal expansion (the natural expansion of water as global warming heats the oceans), melting polar ice in Greenland and Antarctica, and Mountain glaciers account for the other two-thirds.
Austermann has carefully observed the melting of polar glaciers, pointing to West Antarctica’s Thwaites Glacier as a top concern for scientists.
“There is good evidence that if it starts to melt, much of the West Antarctic Ice Sheet will [also] Melt,” she explained.
The talk also delves into how and why sea levels are not rising everywhere at the same rate. On the east coast, for example, sea levels are rising at about twice the global rate. Even along the same coastline, this acceleration is not uniform.
“During this time period, sea level rose about two millimeters per year in Florida and about four millimeters a year in the Carolinas,” Osterman said. “Therefore, there is significant spatial variability in sea level projections, which also means that this spatial variability is critical as we plan and adjust infrastructure for sea level change.”
The change, Austermann said, dates back to the last ice age and how land gradually rebounded after the burden of ice eased. When ice sheets covered large swaths of North America, their weight depressed the land under the ice and caused surrounding land to bulge. Now that the ice is gone, the land that used to lie under the ice sheet is slowly rising, and the surrounding bulge is lowering and flattening. This so-called “post-glacial rebound” changes the character of the coast and its relationship to rising sea levels.
“The sea level is rising, and it’s rising because of the expansion, but also because the land is falling. Because of this very unique shape, it’s most severe in the Carolinas,” Osterman said.
A slide from Austermann’s presentation shows how heavy ice sheets deform the surrounding land.
Climate researchers predict a range of future sea levels. Austermann presents a map showing what the different forecasts mean in terms of flooding.
Along the East Coast, sea level rise is fastest in the Carolinas.
Austermann delves into paleoclimatology, studying climates of the past, and describes how scientists at Lamont—including herself and Raymo—are able to model future sea levels by studying markers of past tides and measuring sea levels during times when Earth was rising. Plane rise predictions. warmer than today.Specifically, Austermann shared from Bahamas Field TripThere, the team found clues to rising sea levels in the distant past by examining fossil dunes and corals. They concluded that sea levels were likely at least two millimeters higher then than they are today, and may have risen by as much as five millimeters.
In her final review, there is a daunting conclusion. Sea levels in New York City are expected to rise by around a meter by the end of the century, reminding viewers that reducing carbon emissions is critical to avoiding the most dramatic global changes.
