Tag: Sea Level Rise

Tracking 3 Decades of Dramatic Glacial Lake Growth

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In the largest-ever study of glacial lakes, researchers using a 30-year satellite data record have found that the volume of these lakes worldwide has increased by about 50% since 1990.
Credits: NASA

In the largest-ever study of glacial lakes, researchers using 30 years of NASA satellite data have found that the volume of these lakes worldwide has increased by about 50% since 1990 as glaciers melt and retreat due to climate change.

The findings, published in the journal Nature Climate Change, will aid researchers assessing the potential hazards to communities downstream of these often unstable lakes and help improve the accuracy of sea-level rise estimates by advancing our understanding of how glacial meltwater is transported to the oceans.

Glaciers are retreating on a near-global scale and this study provides scientists with a clearer picture of how much of this water has been stored in lakes.

“We have known that not all meltwater is making it into the oceans immediately,” said lead author Dan Shugar of the University of Calgary in Canada. “But until now there were no data to estimate how much was being stored in lakes or groundwater.” The study estimates current glacial lake volumes total about 37.4 cubic miles (156 cubic kilometers) of water, the equivalent of about one-third the volume of Lake Erie.

Shugar and his collaborators from governments and universities in Canada, the United States, and the United Kingdom, working under a grant from NASA’s High Mountain Asia Program, initially planned to use satellite imaging and other remote-sensing data to study two dozen glacial lakes in High Mountain Asia, the geographic region that includes the Tibetan Plateau and surrounding mountain ranges, including the Himalaya.

“We wrote scripts in Google Earth Engine, an online platform for very large analyses of geospatial data, to look only at High Mountain Asia, and then decided to look at all glacial lakes in the world,” Shugar said. “From there, we were able to build a scaling relationship to estimate the volume of the world’s glacial lakes based on the area of this large population of lakes.”

The team ultimately analyzed more than 250,000 scenes from the Landsat satellite missions, a joint NASA/U.S. Geological Survey program. A decade ago it would not have been possible to process and analyze this volume of data. The team looked at the data in five time-steps beginning with 1990 to examine all the glaciated regions of the world except Antarctica and analyze how glacial lakes changed over that period.

Shugar points out that while water from melting glaciers stored in glacial lakes is a relatively small contributor to overall sea level rise, it can have a major impact on mountain communities downstream of these glacial lakes.

Glacial lakes are not stable like the lakes in which most people are used to swimming or boating because they are often dammed by ice or glacial sediment called a moraine, which is composed of loose rock and debris that is pushed to the front and sides of glaciers. Rather, they can be quite unstable and can burst their banks or dams, causing massive floods downstream. These kinds of floods from glacial lakes, known as glacial lake outburst floods, have been responsible for thousands of deaths over the past century, as well as the destruction of villages, infrastructure, and livestock. A glacial lake outburst flood affected the Hunza Valley in Pakistan in May 2020.

“This is an issue for many parts of the world where people live downstream from these hazardous lakes, mostly in the Andes and in places like Bhutan and Nepal, where these floods can be devastating,” Shugar said. “Fortunately, organizations like the United Nations are facilitating a lot of monitoring and some mitigation work where they’re lowering the lakes to try and decrease the risks.”

In North America, the risks posed by a glacial lake outburst flood are lower.

“We don’t have much in the way of infrastructure or communities that are downstream,” Shugar said. “But we’re not immune to it.”

For more information about NASA’s Earth science programs, visit https://www.nasa.gov/earth.

Arctic heating races ahead of worst-case estimates

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Arctic heating is happening far faster than anybody had anticipated. And the ice record suggests this has happened before.

September 2, 2020 by Tim Radford, Climate News Network (CC BY-ND 4.0)

Svalbard, in whose waters temperatures have risen at 1.5°C every decade for the last 40 years. Image: By Vince Gx on Unsplash
Svalbard, in whose waters temperatures have risen at 1.5°C every decade for the last 40 years. Image: By Vince Gx on Unsplash

LONDON, 2 September, 2020 – An international team of scientists brings bad news about Arctic heating: the polar ocean is warming not only faster than anybody predicted, it is getting hotter at a rate faster than even the worst case climate scenario predictions have so far foreseen.

Such dramatic rises in Arctic temperatures have been recorded before, but only during the last Ice Age. Evidence from the Greenland ice cores suggests that temperatures rose by 10°C or even 12°C, over a period of between 40 years and a century, between 120,000 years and 11,000 years ago.

“We have been clearly underestimating the rate of temperature increases in the atmosphere nearest to the sea level, which has ultimately caused sea ice to disappear faster than we had anticipated,” said Jens Hesselbjerg Christensen, a physicist at the University of Copenhagen in Denmark, one of 16 scientists who report in the journal Nature Climate Change on a new analysis of 40 years of data from the Arctic region.

They found that, on average, the Arctic has been warming at the rate of 1°C per decade for the last four decades. Around Norway’s Svalbard archipelago, temperatures rose even faster, at 1.5°C every 10 years.

We have been clearly underestimating the rate of temperature increases in the atmosphere nearest to the sea level, which has ultimately caused sea ice to disappear faster than we had anticipated.”

—Jens Hesselbjerg Christensen, Physicist, University of Copenhagen

During the last two centuries, as atmospheric levels of carbon dioxide climbed from an average of around 285 parts per million to more than 400ppm, so the global average temperature of the planet rose: by a fraction more than 1°C.

The latest study is a reminder that temperatures in the Arctic are rising far faster than that. And the news is hardly a shock: within the past few weeks, separate teams of researchers, reporting to other journals, have warned that Greenland – the biggest single reservoir of ice in the northern hemisphere – is melting faster than ever; more alarmingly, its icecap is losing mass at a rate that suggests the loss could become irreversible.

Researchers have also confirmed that the average planetary temperature  continues to rise inexorably, that the Arctic Ocean could be free of ice in  summer as early as 2035, and that the climate scientists’ “worst case” scenarios are no longer to be regarded as a warning of what could happen: the evidence is that what is happening now already matches the climate forecaster’s worst case. The latest finding implicitly and explicitly supports this flurry of ominous observation.

“We have looked at the climate models analysed and assessed by the UN Climate Panel,” said Professor Christensen. “Only those models based on the worst case scenario, with the highest carbon dioxide emissions, come close to what our temperature measurements show over the past 40 years, from 1979 to today.” – Climate News Network

Oceanographer John Englander Discusses Sea-Level Rise

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John Englander is an oceanographer, consultant, and leading expert on sea-level rise. His broad marine science background, explorations to Greenland and Antarctica, and research provide him the ability to see the big picture of sea-level rise and its societal impacts.

In this clip, John points out that various tipping points appear to be cascading. Some examples he cites include the Arctic sea ice melting quicker. It is responsible for changing weather patterns and could be involved with slowing down the ocean currents.

He points out that the number of people that are vulnerable to flooding as sea-level rises is difficult to define. If sea-level becomes one meter higher or one point one meters higher, the extra 10 centimeters is hard to extrapolate or project onto how many homes would flood. Today, satellite images provide a more accurate picture of the height of the terrain the topography. In prior years, tree canopy looked like land and flooding projections were more conservative. Now, artificial intelligence and machine learning, help us decipher the actual land height and acknowledge that more people are vulnerable to flooding.

He points out that even if we could somehow magically stop all carbon dioxide emissions, we would still have the effects of the heat already stored in the atmosphere. All the strange weather patterns, the fires, and droughts, will not go away immediately even if we could reduce carbon dioxide emissions to zero. Therefore, we have to be more resilient to these extreme weather events.

John works with businesses, governmental agencies and communities to understand the risks of increased flooding due to rising seas, extreme tides, and severe storms, advocating for “intelligent adaptation”.