He and his colleagues declined to comment for this story in keeping with an academic custom not to discuss new work with the press before its publication. The new results inform one of the biggest outstanding questions—and most fervent debates—concerning how climate change will reshape our world: How much will the seas rise, and how fast will that upheaval occur?
DeConto and several other American glaciologists—including Richard Alley , a professor at Penn State and a co-author of the new research—represent something like the vanguard of that discussion. By the middle of next century, they warn, this mechanism could send ocean levels soaring at a rate of several feet per decade. For reference: Along the U. East Coast, the Atlantic Ocean has risen by only about a foot over the last 12 decades.
It holds that warm ocean waters will eventually chew away the floating ice shelves that gird Antarctic glaciers today. With these ice shelves gone, the glaciers will stand naked on the seafloor: towering, fragile cliffs of ice. Imagine a foot-tall shard of sapphire rising from the ocean and stretching for miles in both directions, and you will have a sense of the awesome prospect of this new geography.
You will also have a sense of its dangerous physics, because ice cannot support itself at such heights. As MICI kicks in, those sapphire walls will crack, buckle, and begin rapidly birthing hundred-foot splinters of frozen freshwater into the sea. And thus the oceans will rise.
Other researchers find this possible future somewhat fantastic. In its last major report, in , the Intergovernmental Panel on Climate Change projected that oceans could rise two feet by if greenhouse-gas emissions continue on a worst-case trajectory. So, when the sea level rises, people will be affected in different ways, depending on where they live. The UK is used to occasionally dealing with rising sea level for short periods of time, particularly when there are storms at the same time as when the tides higher than usual.
If the IPCC predictions are correct, we must consider the possible increase in sea level on top of natural tidal surges. This will cause dangerously high tides to occur more often in the coming decades, and these future tides might be more destructive than we are used to. In farming regions near the coast, seawater flooding on land can contaminate the soils with salt, making them less able to support the growth of crops. The salty water may also get into underground stores of fresh water known as groundwater , which is the source of important drinking water and also for farmers to grow crops.
In coastal cities, sea level rise will cause more flooding to houses, businesses, and while it may seem sensible to consider moving cities away from harmful floods, especially as we know it will likely happen in the future, our cities cost so much to develop that we are more likely to simply try to protect them from rising sea levels.
A vision of our cities near the sea involves them with walls facing the ocean several meters high, with the street level of the cities themselves being below the level of the ever rising sea. Sea level rise has been measured across the world since This is due to global warming caused by greenhouse gas emissions from the burning of coal, oil, and gas. The change since is small compared to sea level changes that occurred further back in time, however. During the ice age 20, years ago, sea level was m lower than it is today.
This shows us two things 1 that substantial changes to sea level are possible and 2 when the climate warms, the ice melts and sea level goes up. In the future, sea level will continue to rise, possibly by as much as 1 m by the end of this century, if we do not reduce our greenhouse gas emissions. Such change poses great problems for the million people who live close to the sea. It will affect our ability to grow crops in coastal farms, make it difficult to maintain the quality of drinking water, and will alter the way we live in and develop our cities.
The world has around , glaciers. Sea ice grows during the cold winter months and melts during the summer months. The amount of summer sea ice in the Arctic has been reducing in the last few decades; Antarctic sea ice change has been more variable.
This ice came from the ocean, and so the level of the ocean was reduced back then—by m—compared to now. The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. A 20th century acceleration in global sea-level rise. Chapter Sea level change. Stocker, D. Qin, G. By the end of the century, global mean sea level is likely to rise at least one foot 0. In some ocean basins, sea level has risen as much as inches centimeters since the start of the satellite record.
Regional differences exist because of natural variability in the strength of winds and ocean currents, which influence how much and where the deeper layers of the ocean store heat. Between and mean sea level has risen across most of the world ocean blue colors.
In some ocean basins, sea level has risen inches centimeters. Rates of local sea level dots on the coast can be larger than the global average due to geological processes like ground settling or smaller than the global average due to processes like the centuries-long rebound of land masses from the loss of ice-age glaciers. Past and future sea level rise at specific locations on land may be more or less than the global average due to local factors: ground settling, upstream flood control, erosion, regional ocean currents, and whether the land is still rebounding from the compressive weight of Ice Age glaciers.
In the United States, the fastest rates of sea level rise are occurring in the Gulf of Mexico from the mouth of the Mississippi westward, followed by the mid-Atlantic. Only in Alaska and a few places in the Pacific Northwest are sea levels falling, though that trend will reverse under high greenhouse gas emission pathways.
In the United States, almost 40 percent of the population lives in relatively high population-density coastal areas, where sea level plays a role in flooding, shoreline erosion, and hazards from storms. Atlas of the Oceans.
South Beach, Miami on May 3, In urban settings along coastlines around the world, rising seas threaten infrastructure necessary for local jobs and regional industries. Roads, bridges, subways, water supplies, oil and gas wells, power plants, sewage treatment plants, landfills—the list is practically endless—are all at risk from sea level rise. Explore past and future frequency of high-tide flooding at U. Climate Resilience Toolkit. Nuisance flooding in Annapolis in Around the U. Photo by Amy McGovern.
In the natural world, rising sea level creates stress on coastal ecosystems that provide recreation, protection from storms, and habitat for fish and wildlife, including commercially valuable fisheries. As seas rise, saltwater is also contaminating freshwater aquifers , many of which sustain municipal and agricultural water supplies and natural ecosystems.
Global warming is causing global mean sea level to rise in two ways. First, glaciers and ice sheets worldwide are melting and adding water to the ocean. Second, the volume of the ocean is expanding as the water warms. A third, much smaller contributor to sea level rise is a decline in the amount of liquid water on land—aquifers, lakes and reservoirs, rivers, soil moisture.
This shift of liquid water from land to ocean is largely due to groundwater pumping. In the early 20th century, the glacier met the water and calved icebergs into a marginal lake near the bay. By , the glacier had retreated, leaving behind sediment allowed the lake to be transformed into a small grassland. Photos courtesy of Louis H. Pedersen and Bruce F. Large images: From the s up through the last decade or so, melting and heat expansion were contributing roughly equally to observed sea level rise.
But the melting of mountain glaciers and ice sheets has accelerated:. As a result, the amount of sea level rise due to melting with a small addition from groundwater transfer and other water storage shifts from — was nearly twice the amount of sea level rise due to thermal expansion.
Melt streams on the Greenland Ice Sheet on July 19, Ice loss from the Greenland and Antarctic Ice Sheets as well as alpine glaciers has accelerated in recent decades. Sea level is measured by two main methods: tide gauges and satellite altimeters. Tide gauge stations from around the world have measured the daily high and low tides for more than a century, using a variety of manual and automatic sensors.
Using data from scores of stations around the world, scientists can calculate a global average and adjust it for seasonal differences. What does the U. The radically transformed map would lose 28, square miles of land, home today to Click on the image above to check for threats from sea level rise and storm surge.
These figures come from Climate Central research published in , analyzing and mapping every coastal city, county and state in the lower 48 states. A next generation of research is currently under way. More than half of the area of 40 large cities population over 50, is less than 10 feet above the high tide line, from Virginia Beach and Miami the largest affected , down to Hoboken, N. Twenty-seven of the cities are in Florida, where one-third of all current housing sits below the critical line — including 85 percent in Miami-Dade and Broward counties.
Each of these counties is more threatened than any whole state outside of Florida — and each sits on bedrock filled with holes, rendering defense by seawalls or levees almost impossible. By the metric of most people living on land less than 10 ft above the high tide line, New York City is most threatened in the long run, with a low-lying population count of more than , Sixteen other cities, including New Orleans, La.
Petersburg, Fla.
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