How Sea Level Rise Impacts the Rotation of Our Planet
Scientists may be about to resolve one of the trickiest—and least obvious—questions of climate change: its effect on the rotation of the planet and therefore on the length of the day.
That doesn’t mean scientists have an answer, and if they get one, it is likely to be measured in units of time that are vanishingly small. But even if the answer is insignificant, the attempt to resolve the question is a measure of the intricacy, impact and reach of global warming as a consequence of the human combustion of fossil fuels. It even affects the axis of the planet and it changes our days.
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Jerry Mitrovica, a planetary scientist at Harvard University, and colleagues report in the journal Science Advances that they have managed to make a connection between global sea level rises of the past and the rotation of the Earth on its year-long journey around the sun.
More precisely, they have addressed a 13-year-old puzzle known as Munk’s enigma. This study raised a simple question that cannot be answered simply: if changes on the Earth’s surface slow its rotation, surely it should be possible to detect the contribution of sea level rise?
Almost anything can affect the rotation of the planet: the 2011 Tohoku earthquake and tsunami shortened the day by 1.8 millionths of a second, but the advance and retreat of the ice ages would also have altered the clocks had there been any clocks at the time and the daily ocean tides have for billions of years been making the day drag on.
Fossil corals reveal that a year in the Devonian period 400 million years ago lasted more than 400 days. Now there are only 365 and a bit.
Astronomers have checked ancient Babylonian, Chinese, Greek and Arab records of solar eclipses and used them to make a relatively precise calculation of the rate at which the Earth’s rotation has slowed.
They have arrived at an answer: since 500 BC, Earth time and universal time have diverged by 16,000 seconds, or 4.5 hours.
The measurement of time remains one of mankind’s oldest headaches. The second is, by its first definition, a division of the minute and the hour and a day is defined as 24 hours. This means that if the Earth slows, the day gets longer and so does the second.
That is why astronomers agreed to fix the second at a precise division of the year 1820 and call that universal time. And then when that wasn’t precise enough, they fixed it to the number of vibrations in a caesium-133 atom at a precise temperature.
But that then divorced the second from the 24 hours of the day. Which is why, every so often—the latest was in July 2015—the time lords of the international scientific bureaucracy had to insert a leap second to keep universal and terrestrial time in step.
Since 1972, there have been a total of 26 leap seconds to keep the two ways of measuring time in synchronicity.
Then, in 2002, Walter Munk of the Scripps Institution of Oceanography in San Diego asked the question: if 40,000 billion tons of ice turned into rising sea levels and were changing the axis and rotation of the planet, could the effect be measured? And since it could not be measured accurately, why not?
Re-Examination Is Required
The Harvard authors now think they have an answer: the estimates on which Munk’s paper was based need to be re-examined. This re-examination involves geophysics, archaeo-astronomy and micro-measurement.
It involves dynamic processes far below the Earth’s crust, as well as a new and closer look at the message from the ancient observations of eclipse and more detailed scrutiny of the data of sea level rise.
That doesn’t mean they have an answer to the effect of climate change upon the rotation of the Earth, but when they do, it is likely to be measured in millionths of a second per year.
So people need not adjust their watches. But the study is an indicator of the sheer range of questions raised in pursuit of the wider understanding of the science of global climate. And there may even be a payoff in terms of more accurate climate prediction.
As the Harvard team concludes, “Confronting Munk’s elegant statement of the enigma has thus improved our understanding of Earth’s rotation spanning the last three millennia and the individual sources of sea-level rise in the century before the early 1990s. The reconciliation also adds confidence to ongoing efforts to project this rise to the end of the current century and beyond.”
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Cooking has always intimidated me. As a child, I would anxiously peer into the kitchen as my mother prepared Christmas dinner for our family.
Falling in Love With Food All Over Again<p>Slowly, through my most intimate relationships with friends and partners, I began to see the beauty — and rewards — of cooking.</p><p>I got tired of giving in to defeat and always bringing chips or paper products to social gatherings. I started asking my mom to send me her Christmas and Thanksgiving recipes. I even volunteered to host Thanksgiving dinner at my place.</p><p>Each time I heard my loved ones sing the praises of the foods I prepared for them, I felt a tinge more confident that I could carry out our traditions my way.</p><p>In reaching out to other relatives for their favorite recipes, I learned that they had a little help of their own. They didn't rely solely on their ancestral cooking instincts. They turned to Black chefs for guidance.</p><p>These 7 cookbooks by Black chefs have inspired my family and fed us in nutrients, joy, and spiritual sustenance. They're also helping me overcome my personal fears of cooking.</p>
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The conclusion to decades of work to remove a dam on the Middle Fork Nooksack River east of Bellingham, Washington began with a bang yesterday as crews breached the dam with a carefully planned detonation. This explosive denouement is also a beginning.
The History<p>The Middle Fork Nooksack drains glacier-fed headwater streams that run off the icy summit of 10,778-foot Mt. Baker. The Middle Fork joins the North Fork and then the mainstem of the Nooksack River, which travels to Bellingham Bay and Puget Sound. The entire Nooksack watershed stretches 830 square miles across Washington and into British Columbia.</p>
A Plan Comes Together<p>The Middle Fork dam is not a pool dam built for water storage. Much of the time, water flows over the top until dam operators drop a floodgate to divert water to new locations. That water travels about 14 miles through tunnel and pipeline to Mirror Lake, then Anderson Creek, and to Lake Whatcom before finally being delivered to residents' taps.</p><p>Before removing the dam, engineers had to move the water intake 700 feet upstream and situate it at an elevation that still enabled city water withdrawals throughout the year, regardless of flow conditions.</p><p>They also needed to make sure that the rushing water didn't sweep up fish and accidentally send them through the water-supply system.</p><p>"The solution required a fairly complex design in the intake structure, including a fish exit pipe out of that structure to put fish back into the river in a way that meets current environmental permit standards," explains LaCroix.</p>
Project layout for the removal of the Middle Fork Nooksack diversion dam and rebuilding of water intake. City of Bellingham<p>Despite the cost and the work, she says, being able to continue to meet their municipal water obligations while opening up habitat for threatened species has been a win-win.</p><p>"I think there's a lot of benefits to having a dam removal versus fish passage — the main one being that you get a free-flowing river that can be a dynamic ecosystem and change over time," she says. "A static fish ladder just can't provide that same level of ecosystem benefit."</p>
Restoration Success<p>Despite local authorities' championing dam removal on the Middle Fork, the project has largely flown under the radar, overshadowed in the Pacific Northwest by heated discussions about a much larger potential project — removing <a href="https://www.seattletimes.com/seattle-news/feds-reject-removal-of-4-snake-river-dams-in-key-report/" target="_blank">four federal hydroelectric dams on the lower Snake River</a>, a major tributary of the Columbia River.</p><p>Proponents of dam removal there see it as the best chance for recovering threatened salmon populations, including Chinook, which could help starving Southern Resident killer whales. Those dams also provide irrigation water, barge navigation and hydropower, so there's been more pushback against removal efforts.</p><p>Previous dam removals around the country, however, have proved successful at aiding fish recovery and river restoration.</p><p>Most notably the 1999 demolition of <a href="https://therevelator.org/edwards-dam-removal/" target="_blank">Edwards Dam on Maine's Kennebec River</a> restored the annual run of alewives, a type of herring essential to the food web. The fish run has gone from zero to 5 million in the two decades since dam removal. Blueback herring, striped bass, sturgeon and shad have also extended their reach. And the resurgence has brought back osprey, bald eagles and other wildlife, too.</p><p>The overwhelming success of river restoration on the Kennebec helped to spur a nationwide dam removal movement that's now seen 1,200 dams come down since 1999. Last year a record <a href="https://www.americanrivers.org/conservation-resource/a-record-26-states-removed-dams-in-2019/" target="_blank">90 dams</a> were removed in 26 states, including <a href="https://therevelator.org/cleveland-forest-dam-removal/" target="_blank">20 dams in California's Cleveland National Forest</a>.</p>
Spider excavators remove on dam on San Juan Creek in California's Cleveland National Forest. Julie Donnell, USFS<p>The results have been seen in the Pacific Northwest, as well, which boasts the largest dam removal thus far in the country. In 2011 and 2014, the demolition of <a href="https://therevelator.org/elwha-dam-removal/" target="_blank">two dams</a> on Elwha River, which runs through Washington's Olympic National Park, opened up 70 miles of habitat that had been blocked for a century. Scientists have started seeing all five species of salmon native to the river coming back, particularly Chinook and coho. Bull trout, they've observed, have increased in size since the dams were removal.</p>
Benefits on the Middle Fork Nooksack<p>McEwan hopes to see a similar outcome on the Middle Fork.</p><p>Like the Elwha the Middle Fork Nooksack is a relatively pristine river with little development, and dam removal is expected to provide a big boost to fish. The additional miles of spawning habitat are important, but so is the temperature of that water.</p><p>The dam removal will open access to cold upstream waters, which are ideal for salmon and getting harder to come by as climate change warms waters and reduces mountain runoff.</p><p>"This is really great for the climate change resiliency for these species," says McEwan.</p><p>Steelhead will get back 45% of their historic habitat in the river, and scientists expect Chinook populations to increase in abundance by 31%.</p><p>That <em>could</em> help Southern Resident killer whales.</p><p>"When you get to the ocean, it's a little bit of a black box in terms of what you can model and say definitively is going to help, but more fish is better for orcas," McEwan says.</p><p>Upstream habitat will see benefits, too.</p><p>Oceangoing fish like salmon enrich their bodies with carbon and nitrogen while at sea. When they return to their natal rivers to spawn and die, the marine-derived nutrients they carry back upriver become important food and fertilizer for both riverine and terrestrial ecosystems — aiding everything from trees to birds to bears.</p><p>"Once the fish start making their way back, it will start changing the whole ecological system," says Delgado.</p><p><span></span>But any ecological benefit from salmon restoration, either in the ocean or the upper watershed, won't be immediate.<br></p><p>"The population of salmon on the Middle Fork is so low that we expect it's going to take quite a while to rebound," she says. "But the big picture is that what's good for salmon is good for the region — our history and our destiny are intricately intertwined."</p><p>After decades of work, that process of restoration has finally begun.</p>
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It can grow to a maximum of six inches (16 centimeters), change color depending on mood and habitat, and, like all seahorses, the White's seahorse male gestates its young. But this tiny snouted fish is under threat.
Building an Ocean Seahorse Destination<p>Seahorses are found in tropical and temperate coastal water worldwide, but are most abundant around Australia, China and the Philippines. </p><p>Trade in the tiny creatures is strictly regulated because of their use in traditional medicine, aquariums and their sale as dried curios. But because they are poor swimmers and cannot easily move elsewhere, habitat loss is a particular threat for these curious animals. </p><p>Seahorses wrap their tails around seagrass and corals to avoid being carried away on currents. They use the habitat to spawn and hide from predators such as crabs, while also feeding on riches of plankton and small crustaceans living in the reef.</p><p><span></span>Where corals aren't available, <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/aqc.1217" target="_blank">scientists</a> found seahorses taking up residence in fishing nets and old crab traps abandoned at the bottom of the ocean. </p>
Mixing With the Locals<p>Baby seahorse mortality is high in the wild because they are easily caught, so those bred in the protected environment of the aquarium weren't ready to be released into the wild until early May.</p><p>The team released 90 new arrivals into Sydney Harbor, placing some directly into the purpose-built hotels, and others onto a net that wild seahorses had already settled on.</p><p>Before setting them free, the researchers marked each young seahorse with a fluorescent tag with unique IDs inserted just beneath the skin to track how they get on in the different environments. </p><p>"The most exciting part was being able to put these animals into the wild and then go back a month later and still see them surviving and growing," said McCracken. </p><p>The seahorses will be old enough to mate and reproduce around October or November 2020. And researchers hope that by then, they will be able to breed with the wild population. </p>
Building a Global Seahorse Hotel Chain<p>With seahorses everywhere facing the loss of their coral reef homes, similar projects have sprung up in places like Greece and South Africa, home to the world's most endangered seahorse, the Knysna seahorse. </p><p>"The endangered South African seahorse is benefiting from something quite similar, even though it wasn't intentional," said Peter Teske, professor at the Department of Zoology, University of Johannesburg.</p><p>In the South African <a href="https://www.researchgate.net/publication/322649251_An_endangered_seahorse_selectively_chooses_an_artificial_structure" target="_blank">case</a>, seahorses have bedded down in "Reno mattresses" — wire cages filled with rocks — that were used to build a new marina. Researchers from NGO Knysna Basin Project found the structures acted as a refuge for the animals.<span></span></p><p><span></span>While Teske describes the seahorse hotels as "a positive news story" and a great way to create public awareness of conservation, he added that establishing artificial habitats in some areas will only prevent the extinction of local populations.</p><p>"For a complete recovery, it is necessary to give the natural habitat a chance to regenerate," said the seahorse expert. </p>
Underwater Mascot<p>In Australia, the researchers hope the project could provide an opportunity to raise awareness not only of the plight of the Sydney seahorses but the other animals with which it shares its ocean habitat.</p><p>The waters around Sydney and the east coast are rich in biodiversity and include several threatened species like the weedy seadragon — a relative of the seahorse — and the grey nurse shark. Like the seahorse, they're also under pressure from pollution, ocean traffic and habitat loss through storms and coastal construction. </p><p>"It's a good thing to get people's support and interest. The seahorses are a useful vehicle to get people concerned if the harbor is in trouble," said David Booth, professor of marine ecology at the University of Technology Sydney who is also working on the project. </p><p>The hotels have become an attraction for divers hoping to catch a glimpse of these small but near mythical creatures. </p><p>"Everyone loves seahorses," added Booth, "they are so popular." </p>
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