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Lakes collapse and release meltwater during winter causing inland ice to speed up in Greenland, finds study – Phys.org

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Greenland. Credit: Unsplash/CC0 Public Domain

A team of international researchers has shown for the first time how 18 meltwater lakes in Greenland collapse during winter, which causes the edges of the ice to flow faster. The new knowledge is essential for understanding how climate change influences the flow of ice masses in the Arctic.

In the middle of in 2018, an almost 50-year-old meltwater lake disappeared from the ice sheet in western Greenland. The lake was covered by snow and ice when it collapsed but stored inside. The water disappeared into newly formed cracks and drifted down through the approximately 2 km thick layer of ice. The water hit the rock bed under the ice and flowed out from under the ice sheet toward the sea.

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This meltwater acted as lubrication between the rock bed and the thick ice on top. As a result, the large mass of ice could slide faster toward the coast, accelerating an unusually large region of inland ice. The drainage of this lake caused several other lakes in the adjacent area to collapse too. In total, the collapsed lakes have released approximately 180 million tons of meltwater that has ended up in the world’s oceans.

This activity is shown by new international research based on and led by the French Université Grenoble Alpes with contributions from DTU Space at The Technical University of Denmark (DTU). The study has just been published in Geophysical Research Letters.

“The meltwater lakes on the ice sheet form in the summer when the ice on the surface melts. It is well known that these lakes can collapse and drain during summer. But, surprisingly, this takes place in the winter too. This is the first time that it has been shown that these specific lake drainages cause large ice accelerations during winter when temperatures are very low,” says postdoc and researcher Nathan Maier, lead author of the article.

As a researcher at the Université Grenoble Alpes in France, he led the extensive international research collaboration behind the discovery. He is now a researcher at Los Alamos National Laboratory in the U.S.

“In total, the lakes drained in connection with this incident have resulted in 180 million tons of water flowing into the sea. This is roughly equivalent to the contents of 80,000 Olympic swimming pools measuring 50 by 25 by 2 meters,” states Nathan Maier.

The 50-year-old lake, which was the first to drain, was located approximately 160 km inland, high on the ice sheet. The lake consisted of melted water and had a frozen ice lid because of the cold winter temperatures. When it collapsed, and the water flowed underneath the ice toward the coast of western Greenland, it started a cascade of events that caused other lakes to be drained of their water too. Among other things, the pressure from the water that ran under the ice from the 50-year-old lake probably helped to form further cracks in the ice above, making these lakes leak as well.

18 lakes drained in an area about three times the size of greater London

A total of 18 lakes collapsed accelerating a 5,200 square kilometers area of the ice sheet, corresponding to more than three times the size of greater London. The researchers note that it happened across a month in the winter of 2018 when air temperatures were below freezing.

“We have only investigated a limited area, but we have good reason to assume that similar events take place in many more places in Greenland. If this applies to larger parts of the ice sheet, it could be quite large amounts of meltwater that disappear in this way and cause the ice sheet to slide faster towards the sea,” says Jonas Kvist Andersen, a postdoctoral researcher at DTU Space in Denmark and co-author of the article.

The investigated area primarily includes the large Jakobshavn Isbræ, which flows into the sea in western Greenland and is the fastest flowing glacier in the world, as well as a smaller glacier south of it that ends on land.

Unknown if winter drainages will become more prevalent

It seems obvious to conclude that the lakes have started to collapse in winter due to global warming. Especially when an almost 50-year-old lake is suddenly drained in the middle of winter and the meltwater ends up in the sea and contributes to sea level rise. But that is not a given, according to the researchers.

“It is still unknown if drainages like these will become more prevalent in a warmer future and then contribute further to ice sheet mass loss. More research is needed to get a better understanding of the mechanisms, or triggers, that cause the lakes to drain,” says Nathan Maier.

“Right now, our understanding of how surface melting will affect mass loss from Greenland in the future is based entirely on the assumption that melting only affects the speed of the ice flow during summer. Our discovery, that large accelerations in the ice flow caused by stored meltwater that drains during winter, significantly changes how we understand ice sheet hydrology over annual time scales.”

The researchers have arrived at the new results by analyzing large amounts of radar data and satellite optical images.

Winter meltwater drain should be included in new climate models

It is not only the oldest lakes that collapse after existing for decades. There are several types of cycles, according to the scientists. Some lakes form and collapse within a year; for others, it happens every few years.

The collapsed lakes affect the ice sheet, or glacier, melting in Greenland in several ways. The water from the lakes ends up in the sea. The water lubricates the ice sheets from beneath causing them to slide faster towards the coast exposing them to additional melting. In addition, the structure of the enormous ice masses changes. There could be other mechanisms at play as well.

“It is essential to describe what happens when the melting process takes place in winter so that this knowledge can be included in future models for ,” states Jonas Kvist Andersen.

Draining lakes and waterflow found with radar data and satellite optical images

The researchers have used Synthetic Aperture Radar (SAR) interferometry based on data from the Sentinel-1 satellites from the European Space Agency (ESA) to map how the 18 lakes on the ice sheet in western Greenland have been drained, and how the water from them has subsequently flowed downwards and out to sea.

Visual and optical photos have been retrieved from other European and US satellites. They have been used to identify the lakes and their change over a few months in the winter of 2018. The radar images have been supplemented with photos from older satellites. In this way, it was possible for the scientists to follow the development of the lakes over several decades, including establishing when they were drained.

The Sentinel-1 satellites, which cover the Arctic from an orbit just under 700 km above Earth, have a SAR unit, which sends radar signals obliquely down towards the surface of the , from where they are returned to the satellite.

By analyzing differences and displacements in the radar signal phase, it is possible to measure the movement of the ice surface relative to the satellite. When several measurements are compared, a distinction can be made between horizontal movement (when the ice flow is accelerated) and vertical movement (when the meltwater pushes the overlying ice upwards).

This way, information is obtained about the movement of the meltwater and the ice after the water has drained from the bottom of the .

More information:
Nathan Maier et al, Wintertime supraglacial lake drainage cascade triggers large‐scale ice flow response in Greenland, Geophysical Research Letters (2023). DOI: 10.1029/2022GL102251

Citation:
Lakes collapse and release meltwater during winter causing inland ice to speed up in Greenland, finds study (2023, February 21)
retrieved 21 February 2023
from https://phys.org/news/2023-02-lakes-collapse-meltwater-winter-inland.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

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Joint NASA, CNES Water-Tracking Satellite Reveals First Stunning Views – Space Ref

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This visualization shows water features on New York’s Long Island – shown as bright pink splotches. Purple, yellow, green, and dark blue shades represent different land elevations, while the surrounding ocean is a lighter blue. The data was collected on Jan. 21, 2023, by SWOT’s KaRIn instrument. Credit: NASA/JPL-Caltech

The Surface Water and Ocean Topography mission offers the first taste of the detailed perspectives of Earth’s surface water that its cutting-edge instruments will be able to capture.

The international Surface Water and Ocean Topography (SWOT) mission – led by NASA and the French space agency Centre National d’Études Spatiales (CNES) – has sent back some of its first glimpses of water on the planet’s surface, showing ocean currents like the Gulf Stream in unprecedented detail. SWOT is also capturing views of freshwater features such as lakes, rivers, and other water bodies down to about 300 feet (100 meters) wide.

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The satellite will measure the elevation of nearly all the water on Earth’s surface and provide one of the most comprehensive surveys yet of our planet’s surface water. SWOT’s measurements of freshwater bodies and the ocean will provide insights into how the ocean influences climate change and the water cycle; how a warming world affects water storage in lakes, rivers, and reservoirs; and how communities can better manage their water resources and prepare for floods and other disasters.

“SWOT’s advanced imagery will empower researchers and advance the way we manage fresh water and the effects of sea level rise across the globe,” said NASA Administrator Bill Nelson. “Water is one of our planet’s most important resources – and it’s proven to be vulnerable to the impacts of climate change. SWOT will provide critical information that communities can use to prepare for the impacts of a warming climate.”

A Whole New View

As seen in these early images, on Jan. 21, 2023, SWOT measured sea level in a part of the Gulf Stream off the coast of North Carolina and Virginia. The two antennas of SWOT’s Ka-band Radar Interferometer (KaRIn) instrument acquired data that was mapped as a pair of wide, colored strips spanning a total of 75 miles (120 kilometers) across. Red and orange areas in the images represent sea levels that are higher than the global average, while the shades of blue represent sea levels that are lower than average.

For comparison, the new data is shown alongside sea surface height data taken by space-based instruments called altimeters. The instruments – widely used to measure sea level – also bounce radar signals off of Earth’s surface to collect their measurements. But traditional altimeters are able to look only at a narrow beam of Earth directly beneath them, unlike KaRIn’s two wide-swath strips that observe sea level as a two-dimensional map.

The spatial resolution of SWOT ocean measurements is 10 times greater than the composite of sea surface height data gathered over the same area by seven other satellites: Sentinel-6 Michael Freilich, Jason-3, Sentinel-3A and 3B, Cryosat-2, Altika, and Hai Yang 2B. The composite image was created using information from the Copernicus Marine Service of ESA (European Space Agency) and shows the same day as the SWOT data.

KaRIn also measured the elevation of water features on Long Island – shown as bright pink splotches nestled within the landscape. (Purple, yellow, green, and blue shades represent different land elevations.)

“Our ability to measure freshwater resources on a global scale through satellite data is of prime importance as we seek to adjust to a changing climate,” said CNES Chairman and CEO Philippe Baptiste. “In this respect, the first views from SWOT give us a clearer picture than ever before. These data will prove highly valuable for the international scientific community in the fields of hydrology, oceanography, and coastal studies.”

This initial inland image is a tantalizing indication of how SWOT can measure details of smaller lakes, ponds, and rivers in ways that satellites could not before. Such data will be used to produce an extraordinary accounting of the freshwater on Earth’s surface in ways useful to researchers, policymakers, and water resource managers.

“The KaRIn instrument took years to develop and build, and it will collect information on bodies of water across the globe – data that will be freely and openly available to everybody who needs it,” said Parag Vaze, SWOT project manager at NASA’s Jet Propulsion Laboratory in Southern California.

More About the Mission

Launched on Dec. 16, 2022, from Vandenberg Space Force Base in central California, SWOT is now in a period of commissioning, calibration, and validation. Engineers are checking out the performance of the satellite’s systems and science instruments before the planned start of science operations in summer 2023.

The data for these first images was collected by SWOT’s KaRIn instrument, the scientific heart of the satellite. KaRIn has one antenna at each end of a boom that’s 33 feet (10 meters) long. This enables the instrument to look off to either side of a center line directly below the satellite as it bounces microwave signals off Earth’s surface. The returning radar signals arrive at each antenna slightly out of sync, or phase, from one another. When these signals are combined with other information about the antennas and the satellite’s altitude, scientists will be able to map the height of water on Earth’s surface with never-before-seen clarity. KaRIn encountered an issue earlier this year with one of its subsystems; engineers have now resolved the situation, and the instrument is up and running.

SWOT was jointly developed by NASA and CNES, with contributions from the Canadian Space Agency (CSA) and the UK Space Agency. JPL, which is managed for NASA by Caltech in Pasadena, California, leads the U.S. component of the project. For the flight system payload, NASA provided the KaRIn instrument, a GPS science receiver, a laser retroreflector, a two-beam microwave radiometer, and NASA instrument operations. CNES provided the Doppler Orbitography and Radioposition Integrated by Satellite (DORIS) system, the dual frequency Poseidon altimeter (developed by Thales Alenia Space), the KaRIn radio-frequency subsystem (together with Thales Alenia Space and with support from the UK Space Agency), the satellite platform, and ground operations. CSA provided the KaRIn high-power transmitter assembly. NASA provided the launch vehicle and the agency’s Launch Services Program, based at Kennedy Space Center, managed the associated launch services.

To learn more about SWOT, visit: https://swot.jpl.nasa.gov/

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Severe solar storm hits Earth, strongest in past 6 years – Indiatimes.com

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The Earth witnessed a powerful solar storm in nearly six years, causing auroras all over the US, the National Oceanic and Atmospheric Administration (NOAA) said. NOAA had earlier announced moderate G2 storm and G3 conditions between March 23 and 25, but updated it to G4. A severe G4 storm can affect the power grid system with possible widespread voltage control problems; and spacecraft operations with increased possibility of surface charging, and atmospheric drag risk on Low Earth Orbiting (LEO) satellites.

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Parade of five planets on display in B.C. skies Tuesday evening

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Five of the sun’s eight major planets will be lined up on the western horizon this Tuesday just after sunset.

The astronomical delight will comprise Mercury, Venus, Mars, Jupiter and Uranus — all in a visible line from the horizon to the crescent moon.

NASA astronomer Bill Cooke says the best way to get a glimpse is to stand somewhere with a clear view of the western horizon.

The planets will stretch from the horizon to halfway up the night sky.

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Mercury and Jupiter (the first and fifth planets from the sun) will dip below the horizon around 30 minutes after sunset, that is 7:37 p.m. on Tuesday.

The five-planet spread can be seen anywhere on Earth.

Venus, Mars and Jupiter will be the brightest, particularly Venus, and Mars will be closest to the moon. Mercury and Uranus will be the dimmest, so a set of binoculars will be useful.

Uranus is the rarest seen of the planetary lineup.

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