“The global rise in sea levels from melting ice and ocean warming from 1900 to 2000 led to a rate more than twice the average for the years 0 to 1800 – the most significant change,” Rutgers said of the study’s findings. .
The study uses new techniques and focuses on six specific locations in the Northeastern US, including three in New Jersey and one in Connecticut, New York and North Carolina.
This study is the first of its kind to use what the researchers call “sea-level budgets” to determine the rate at which the ocean rises over a long period of time.
A sea level budget examines sea level change over time on a global, regional, and local scale. It indicates how sea level is affected by different phenomena, which are divided into scales. On each of these scales, there are several factors that contribute to the rising water levels, or in some cases the fall.
On a global scale, for example, factors such as water temperatures play a role, while on a local scale, soil subsidence can be taken into account, which can differ per city.
“If you want to know what is driving sea level change, this budget approach is one way to break down those separate components,” said Jennifer Walker, lead author of this study and postdoctoral fellow at Rutgers University.
What this research has shown is that the rising levels at these locations manage to decline over the period studied.
“Regional land sinking was the dominant component of sea level change on those long time scales,” Walker explains.
This land subsidence “is the result of the Laurentide Ice Sheet from our last Ice Age,” Walker told CNN. “The ice sheet receded thousands of years ago and the country is still recovering from the effect of that previous layer.”
“Sea level rise on the US East Coast is higher because of the slowing Gulf Stream,” said Brian McNoldy, a senior research associate at the University of Miami Rosenstiel School of Marine and Atmospheric Science who was not part of the study.
Walker added that for the past 200 years roughly, “We have rates double the average compared to the past 2,000 years … Where it used to be that this regional bottom sinking was the dominant force, it is now this global component that is driven by the melting of ice and the warming of the oceans. “
While sea-level budgets have increased over the past century, some have also declined over time. Before about 1600 of the Common Era, the regional nonlinear budget had a declining sea level percentage. This drop in sea levels is likely caused by “broad climate transitions in the North Atlantic,” the study said. This includes pressure patterns over the North Atlantic, which is basically where the low and high pressure systems are located.
Rates are accelerating due to climate change
These global factors were not a dominant contributor to sea level rise before the year 1800, but that has changed recently. “The increasing influence of the global component is the most significant change in sea-level budgets at all six locations,” the study said.
This means that humans cause the seas to rise and dominate Earth’s systems, scientists say.
The data collected for a location in northern New Jersey shows that from 1400 to 1500 CE, global sea levels likely rose by 0.13 millimeters per year. A few hundred years later, in the period from 1900 to 2000, or the 20th century, the rate increased dramatically to 1.30 millimeters per year.
Meanwhile, regional and local sea level budgets were either constant or showing significantly lower changes.
On a global scale, for example, there have been sea level rises over several centuries, but then declined again. This is a natural cycle. But what happened recently in the 20th century hasn’t been entirely natural due to a more significant, upward acceleration in water levels.
Walker said trends in rising sea levels could be linked to the greenhouse gases already being emitted, and rates will continue to accelerate.
There’s another part of how sea level rise can have a big impact: big storms. Walker noted, “With these big storm events, you can really see the effects better.”
A storm like Hurricane Sandy in 2012 paralyzed much of the Northeast, including New York City, with a record storm surge. “The effects of such a major storm will only get worse on top of (the rising seas).”
Walker said the effects of sea-level rise during major weather events pose a longer-term challenge once levels get even higher.