Tidal shift (5/11/23)

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Changing with the Tides

Up in Greenland, glaciers are melting faster than expected at their edges where they meet the sea. A collection of eyes in space turned their gaze to the frigid North to see why.

As it turns out, glaciers are a lot more affected by tidal patterns than we thought—and that’s leading to ice melting faster than expected, a study led by NASA JPL and UC Irvine researchers and published this week in the Proceedings of the National Academy of Sciences explains.

Glacial motion: The boundary where a glacier no longer sits on a foundation of bedrock, but rather begins to protrude out into the sea, is called its grounding line. Glaciologists generally assume that a glacier’s grounding line stays…well…grounded, and doesn’t shift much with the changing of the tides.

Radar imagery tells a different story. The research team used observations from two radar constellations (the Italian COSMO-SkyMed constellation and the Finnish ICEYE constellation) and the TanDEM-X synthetic aperture radar satellite to pierce through the Petermann Glacier’s surface in northern Greenland to reveal what was happening below.

The result: These radar observations revealed that the Petermann Glacier’s grounding line moves as far as six kilometers between high and low tide.

“This is an order of magnitude larger than expected for grounding lines on a rigid bed,” Enrico Ciraci, UCI assistant specialist in Earth system science, NASA postdoctoral fellow, and lead author on the study said in a release.

When the grounding line moves in and out with the tides, seawater seeps underneath. That warmer seawater melts the glacier from underneath. At Petermann Glacier, water carved a 670-foot cavity between 2016 and 2022 that has not re-frozen.

What it all means: Because of this movement, Petermann Glacier—and, most likely, other glaciers as well—is interacting with seawater far more than anticipated, making it more sensitive to increases in water temperature as the climate changes.

Projections for how quickly glaciers in the far north will need to be adjusted, and right now, the team anticipates a whole lot more of a rise in sea level from glacier erosion—perhaps even twice as much as currently predicted. Using this data and additional observations from radar satellites, the team hopes that researchers can improve their models for sea level rise and glacier ice melting rates.

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Other News from the Cosmos

• The heliosphere, i.e., the magnetic bubble surrounding the Sun, has ripples that are likely affected by solar activity, NASA’s IBEX (Interstellar Boundary Explorer) found.

• Researchers at Penn State cataloged more than a hundred “blazars,” or bright galaxies with supermassive, volatile black holes at their centers.

• Dragonfly, a mission to Titan currently slated for 2024, may be delayed due to proposed budget cuts to the program.

• JWST directly measured the reflective, metallic atmosphere of the hot sub-Neptune type exoplanet GJ 1214b.

• ESO took more than a million infrared images that astronomers used to create a huge galactic atlas, showing five stellar nurseries in detail.

• “Space waves,” which occur when the solar wind hits the Earth’s magnetic shield, could help scientists to understand space weather patterns better.

• Hubble observations of a strange shadow cast on the surface of a disk of gas surrounding a star are explained by a tilted inner disk, potentially influenced by a planet.

• A trail of stars thought to be left by a careening black hole might actually just be a flat galaxy viewed from the side.

• The bubble of high-energy gas that extends above and below the center of the Milky Way is contained by a complex “shell,” researchers at the Ohio State University found.

• Plutonium availability—or the lack of it—could put a damper on NASA’s planned mission to Uranus.

Rachael's Recs

🐭 Tom and Jerry: For decades now, our eyes in space have been keeping close tabs on Earth’s weather patterns and the effects of climate change across the globe. The Grace and Grace-FO (Follow-On) missions have contributed to this mass of data through a unique approach—two satellites, nicknamed Tom and Jerry, circle the globe in a tightly linked polar orbit, collecting data in tandem. The Financial Times detailed this mission and its impacts in an interactive infographic that gets down to the nitty-gritty of its construction and technology.

⚡ Stayin’ alive: Voyager 2 has been hurtling through the void of space, beaming home imagery and data from deep in the cosmos, since its launch in 1977. Now, its power supply is running low—but we’re not giving up on it just yet. In a piece for WIRED, writer Ramin Skibba details the steps that NASA has taken to keep the mission going strong through its 50th birthday (at least).

🤖 AI exploration: ChatGPT’s taken the world by storm, and the effects of AI are already expanding off-world. Machine learning algorithms and AI are transforming the way astronomers gather and interpret signs from the universe. For Axios Space, Miriam Kramer outlines how this brave new world of computing is impacting astronomy.

🏛️ Policy peeps: Payload’s own Jacqueline Feldscher has launched our newest weekly newsletter, Polaris, which homes in on the policy side of space in the same old Payload format and voice you know and (hopefully, at this point) love. Subscribe in one click using the button below to catch the second edition on Tuesday!

The View from Space