Showing posts with label Sea Levels. Show all posts
Showing posts with label Sea Levels. Show all posts

Wednesday, May 5, 2021

Sea level rise is rapid and unstoppable unless Paris Agreement targets met


Aggressive efforts to limit global warming will sharply reduce future sea-level rise, suggests a paper published in Nature. 
Icebergs in Sermilik Fjord, SE Greenland Credit: Donald Slater

A second paper, also published in Nature, indicates that warming of 3 °C could cause sea level to increase by 0.5 cm every year by 2100 as a result of melting Antarctic land ice. The findings provide further insight into the impact of melting land ice on global sea-level rises.

This animation shows the rate at which the ice thickness is changing in meters per year (more red/yellow means faster thinning and thus faster ice loss) as the Antarctic Ice Sheet responds to changes in the atmosphere and ocean due to one potential climate scenario. This simulation, using the BISICLES ice sheet model, represents one of hundreds of such simulations used for this work to characterize ice sheet response to changes in the climate. Credit: Daniel Martin and Courtney Shafer.

Since 1993, land ice has contributed to around half of all global sea-level rise and this contribution is expected to increase as the world warms. The Antarctic Ice Sheet is the largest land ice reservoir and its ice loss is accelerating. Complex ice sheet models can be used to project the contribution of land ice to sea-level rise, but they require massive computational power and cannot explore all possible outcomes, owing to uncertainties in the projections.

Tamsin Edwards and colleagues use a statistical and computationally efficient approach to emulate the behaviour of more-complex models to project glacier and ice sheet contributions to sea-level rise under a range of scenarios. They find that if the ambitious Paris Agreement target of limiting warming to 1.5 °C was met, the contribution of land ice to sea-level rise could be halved by 2100—from the median projected sea-level rise of 25 cm under current climate projections, to 13 cm. The authors also suggest that melting from the Greenland Ice Sheet would fall by around 70% and that the contribution of melting glaciers to sea-level rise would also halve. The authors indicate that there is no clear difference for Antarctica under different emissions scenarios, owing to uncertainties in the competing processes of snowfall accumulation and ice loss. However, if the most extreme ice sheet behaviour is assumed, Antarctic ice loss could be five times higher, which would increase median sea-level rise to 42 cm under current pledges.

In a separate modelling study, Robert DeConto and colleagues find that limiting warming to the Paris Agreement’s alternative target of 2 °C maintains roughly constant Antarctic ice loss at current rates. However, in a scenario with warming of 3 °C—the warming trajectory consistent with current fossil fuel emissions—the authors predict that the rate of ice loss will increase substantially from 2060, triggering sea-level increases of 0.5 cm per year by 2100. Once a threshold of rapid sea-level rise is reached, modelling of optimistic, yet theoretical, approaches to remove carbon dioxide from the atmosphere shows a reduction, but not cessation, of further sea-level rise over the coming centuries.

The two papers highlight that aggressive efforts to limit global warming will sharply reduce future sea-level rise. For Antarctica, Tamsin Edwards and colleagues find that the complexity of competing processes on the ice sheet make it difficult to make concrete predictions about its future, and Robert DeConto and colleagues show that it is keenly sensitive to warming of 3 °C and greater. Thus, for the largest body of ice on the planet, important uncertainties remain.

Saturday, April 10, 2021

Unsettling currents: Warm water flowing beneath Antarctica’s ’Doomsday Glacier'

Science Daily

The calving front of Thwaites Ice Shelf looking at the ice below the water's surface as seen from the NASA DC-8 on Oct. 16, 2012. 

Data from underneath Thwaites Glacier, also known as the Doomsday Glacier. Story here.

Wednesday, September 30, 2020

Unprecedented mass loss expected for the Greenland Ice Sheet


(With some minor editing by PinP.)

The edge of the Greenland Ice Sheet.  Credit: Jason Briner

Mass loss from the Greenland Ice Sheet is predicted to be higher in this century than any time in the past 12,000 years. The simulations, published in Nature, are based on high-carbon-emission scenarios and consider the southwestern region of Greenland. The findings add to a body of evidence that suggests that reducing carbon emissions is needed to decrease the contribution of the Greenland Ice Sheet to sea-level rise.

As the Arctic warms, the Greenland Ice Sheet has been losing mass and contributing to sea-level rise. That loss rate has increased dramatically since the 1990s. But are those rates and ones projected for the future unexpected? Or, are they just related to "natural variability?" To answer that question, Jason Briner and colleagues produced high-resolution simulations based on geological observations covering southwestern Greenland for the past 12,000 years that extend continuously into the future up to 2100.

The Greenland Ice Sheet.  Credit: Jason Briner

The simulations suggest that mass loss from the Greenland Ice Sheet in the twenty-first century will exceed the maximum mass-loss rates from the past 12,000 years. They find the largest losses in the past (between 10,000 and 7,000 years ago) were at rates of around 6,000 billion tonnes per century. That's similar to the estimated rates of the first two decades of this century. 

However, future losses are expected to exceed those maximum rates. Projected mass losses for the rest of this century are in the range of 8,800 to 35,900 billion tonnes. Those are based on the lowest and highest greenhouse gas emissions scenarios, respectively - that is, the amount of ice losses this century could reverse 4,000 years of cumulative ice growth and exceed previous mass-loss rates by about fourfold. The authors conclude that unprecedented rates of mass loss will occur unless a low-carbon-emission scenario is followed.

Monday, March 2, 2020

Climate Change: Life’s a beach - a disappearing one!

A Pexels photo.
Half of the world's beaches, many of which are in densely populated areas, could disappear by the end of the century under current trends of climate change and sea level rise, suggests a paper published in Nature Climate Change

Sandy beaches occupy more than one third of the global coastline and have high socio-economic value. Beaches also provide natural coastal protection from marine storms and cyclones. However, erosion, rising sea levels and changing weather patterns threaten the shoreline, its infrastructure and populations.
Michalis Vousdoukas and colleagues analysed a database of satellite images showing shoreline change from 1984 to 2015. The authors extrapolated historical trends to predict future shoreline dynamics under two different climate change scenarios. They determined the ambient shoreline change, driven by physical factors (geological or anthropogenic) and shoreline retreat due to sea level rise. They also examined how erosion from storms may change under climate change and impact shorelines.  

The results of these analyses indicate that around 50% of the world’s sandy beaches are at risk of severe erosion. The risk for erosion is particularly high in certain countries under both climate scenarios, including The Gambia and Guinea-Bissau, where over 60% of sandy coastline may be lost. When the total length of sandy beach projected to be lost is analysed, Australia would be the worst affected with nearly 12,000 km at risk. Canada, Chile, Mexico, China and the United States would also be greatly affected. Additional research could further improve these estimates, which may be impacted by human intervention.

Tuesday, October 29, 2019

Rising sea levels pose threat to homes of 300m people – study

The Guardian
Photo by Christian Ferrer
Figure based on new analysis of coastlines is more than three times previous estimate. Story here.

Tuesday, October 31, 2017

Lancet Study Warns of Global Health Crisis and 1 Billion Climate Refugees by 2050


"We are only just beginning to feel the impacts of climate change." Story here.

Waves crash against the International Airport of Nauro, 
a small Pacific island country. Photo - Matt Robertson 

Wednesday, September 13, 2017

Global fingerprints of sea-level rise revealed by satellites


Geological processes send more meltwater from glaciers and ice sheets to Earth's mid-latitudes. Story here.

Greenland. Photo by Uffe Wilken

Sunday, July 23, 2017

Satellite snafu masked true sea-level rise for decades

Thursday, May 18, 2017

Sea level rise will double coastal flood risk worldwide

Waves crash against the wall at the end of Nauru International Airport's runway. 
Rising sea levels pose a serious risk coastal erosion for small Pacific island countries, Photo: Matt Robertson / DFAT
Small but unstoppable increases will double frequency of extreme water levels with dire consequences, say scientists. Story here.

Sunday, April 16, 2017

Slice of Greenland ice melts into oblivion


news network
Eastern Greenland. Photo by Algkalv 

Coastal glaciers in terminal decline as Greenland ice runs into the ocean and threatens to raise sea levels by the end of the century. Story here.

Tuesday, November 22, 2016

Global sea ice has reached a record low – should we be worried?


It’s an internet sensation. An alarming graph showing the global area of sea ice falling to unprecedented lows for this time of year has gone viral. Story here.

Thursday, November 3, 2016

Ghost Forests: How Rising Seas Are Killing Southern U.S. Woodlands


A steady increase in sea levels is pushing saltwater into U.S. wetlands, killing trees from Florida to as far north as New Jersey. But with sea level projected to rise by as much as six feet this century, the destruction of coastal forests is expected to become a worsening problem worldwide. Story here.

Thursday, March 31, 2016

Scientists Nearly Double Sea Level Rise Projections For 2100

The Washington Post
Sea levels could rise nearly twice as much as previously predicted by the end of this century if carbon dioxide emissions continue unabated, an outcome that could devastate coastal communities around the globe, according to new research published Wednesday. 

The main reason? Antarctica. Details here.

Wednesday, February 24, 2016

Seas Are Rising at Fastest Rate in Last 28 Centuries

The New York Times

The worsening of tidal flooding in American coastal communities is largely a consequence of greenhouse gases from human activity, and the problem will grow far worse in coming decades, scientists reported Monday. Details here.

Thursday, October 9, 2014

NOAA: Record Antarctic Sea Ice Growth Linked To Its Staggering Loss Of Land Ice

NOAA said in a news release Tuesday that “as counterintuitive as expanding winter Antarctic sea ice may appear on a warming planet, it may actually be a manifestation of recent warming.” Details here.

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