Issue 89 - October 2022

Dinosaur-Killing Asteroid Triggered Global Tsunami That Scoured Seafloor Thousands of Miles from Impact Site

By U-Michigan News

Modeled tsunami sea-surface height perturbation, in meters, four hours after the asteroid impact. This image shows results from the MOM6 model, one of two tsunami-propogation models used in the University of Michigan-led study. Credit: From Range et al. in AGU Advances, 2022.

ANN ARBOR—The miles-wide asteroid that struck Earth 66 million years ago wiped out nearly all the dinosaurs and roughly three-quarters of the planet’s plant and animal species.

It also triggered a monstrous tsunami with mile-high waves that scoured the ocean floor thousands of miles from the impact site on Mexico’s Yucatan Peninsula, according to a new University of Michigan-led study.

The study, scheduled for online publication Oct. 4 in the journal AGU Advances, presents the first global simulation of the Chicxulub impact tsunami to be published in a peer-reviewed scientific journal. In addition, U-M researchers reviewed the geological record at more than 100 sites worldwide and found evidence that supports their models’ predictions about the tsunami’s path and power.

“This tsunami was strong enough to disturb and erode sediments in ocean basins halfway around the globe, leaving either a gap in the sedimentary records or a jumble of older sediments,” said lead author Molly Range, who conducted the modeling study for a master’s thesis under U-M physical oceanographer and study co-author Brian Arbic and U-M paleoceanographer and study co-author Ted Moore.

Energy impact

The review of the geological record focused on “boundary sections,” marine sediments deposited just before or just after the asteroid impact and the subsequent K-Pg mass extinction, which closed the Cretaceous Period.

“The distribution of the erosion and hiatuses that we observed in the uppermost Cretaceous marine sediments are consistent with our model results, which gives us more confidence in the model predictions,” said Range, who started the project as an undergraduate in Arbic’s lab in the Department of Earth and Environmental Sciences.

The study authors calculated that the initial energy in the impact tsunami was up to 30,000 times larger than the energy in the December 2004 Indian Ocean earthquake tsunami, which killed more than 230,000 people and is one of the largest tsunamis in the modern record.

The team’s simulations show that the impact tsunami radiated mainly to the east and northeast into the North Atlantic Ocean, and to the southwest through the Central American Seaway (which used to separate North America and South America) into the South Pacific Ocean.

In those basins and in some adjacent areas, underwater current speeds likely exceeded 20 centimeters per second (0.4 mph), a velocity that is strong enough to erode fine-grained sediments on the seafloor.

In contrast, the South Atlantic, the North Pacific, the Indian Ocean and the region that is today the Mediterranean were largely shielded from the strongest effects of the tsunami, according to the team’s simulation. In those places, the modeled current speeds were likely less than the 20 cm/sec threshold.

Modeled tsunami sea-surface height perturbation, in meters, 24 hours after the asteroid impact. This image shows results from the MOM6 model, one of two tsunami-propogation models used in the University of Michigan-led study. Credit: From Range et al. in AGU Advances, 2022.

Geological corroboration

For the review of the geological record, U-M’s Moore analyzed published records of 165 marine boundary sections and was able to obtain usable information from 120 of them. Most of the sediments came from cores collected during scientific ocean-drilling projects.

The North Atlantic and South Pacific had the fewest sites with complete, uninterrupted K-Pg boundary sediments. In contrast, the largest number of complete K-Pg boundary sections were found in the South Atlantic, the North Pacific, the Indian Ocean and the Mediterranean.

“We found corroboration in the geological record for the predicted areas of maximal impact in the open ocean,” said Arbic, professor of earth and environmental sciences. He oversaw the project. “The geological evidence definitely strengthens the paper.”

Of special significance, according to the authors, are outcrops of the K-Pg boundary on the eastern shores of New Zealand’s north and south islands, which are more than 12,000 kilometers (7,500 miles) from the Yucatan impact site.

The heavily disturbed and incomplete New Zealand sediments, called olistostromal deposits, were originally thought to be the result of local tectonic activity. But given the age of the deposits and their location directly in the modeled pathway of the Chicxulub impact tsunami, the U-M-led research team suspects a different origin.

“We feel these deposits are recording the effects of the impact tsunami, and this is perhaps the most telling confirmation of the global significance of this event,” Range said.

Comparing models

The modeling portion of the study used a two-stage strategy. First, a large computer program called a hydrocode simulated the chaotic first 10 minutes of the event, which included the impact, crater formation and initiation of the tsunami. That work was conducted by co-author Brandon Johnson of Purdue University.

Based on the findings of previous studies, the researchers modeled an asteroid that was 14 kilometers (8.7 miles) in diameter, moving at 12 kilometers per second (27,000 mph). It struck granitic crust overlain by thick sediments and shallow ocean waters, blasting a roughly 100-kilometer-wide (62-mile-wide) crater and ejecting dense clouds of soot and dust into the atmosphere.

Two and a half minutes after the asteroid struck, a curtain of ejected material pushed a wall of water outward from the impact site, briefly forming a 4.5-kilometer-high (2.8-mile-high) wave that subsided as the ejecta fell back to Earth.

Ten minutes after the projectile hit the Yucatan, and 220 kilometers (137 miles) from the point of impact, a 1.5-kilometer-high (0.93-mile-high) tsunami wave—ring-shaped and outward-propagating—began sweeping across the ocean in all directions, according to the U-M simulation.

At the 10-minute mark, the results of Johnson’s iSALE hydrocode simulations were entered into two tsunami-propagation models, MOM6 and MOST, to track the giant waves across the ocean. MOM6 has been used to model tsunamis in the deep ocean, and NOAA uses the MOST model operationally for tsunami forecasts at its Tsunami Warning Centers.

“The big result here is that two global models with differing formulations gave almost identical results, and the geologic data on complete and incomplete sections are consistent with those results,” said Moore, professor emeritus of earth and environmental sciences. “The models and the verification data match nicely.”

According to the team’s simulation:

One hour after impact, the tsunami had spread outside the Gulf of Mexico and into the North Atlantic.
Four hours after impact, the waves had passed through the Central American Seaway and into the Pacific.
Twenty-four hours after impact, the waves had crossed most of the Pacific from the east and most of the Atlantic from the west and entered the Indian Ocean from both sides.
By 48 hours after impact, significant tsunami waves had reached most of the world’s coastlines.

Maximum tsunami wave amplitude, in centimeters, following the asteroid impact 66 million years ago. Credit: From Range et al. in AGU Advances, 2022.

Dramatic wave heights

For the current study, the researchers did not attempt to estimate the extent of coastal flooding caused by the tsunami.

However, their models indicate that open-ocean wave heights in the Gulf of Mexico would have exceeded 100 meters (328 feet), with wave heights of more than 10 meters (32.8 feet) as the tsunami approached North Atlantic coastal regions and parts of South America’s Pacific coast.

As the tsunami neared those shorelines and encountered shallow bottom waters, wave heights would have increased dramatically through a process called shoaling. Current speeds would have exceeded the 20 centimeters per second threshold for most coastal areas worldwide.

“Depending on the geometries of the coast and the advancing waves, most coastal regions would be inundated and eroded to some extent,” according to the study authors. “Any historically documented tsunamis pale in comparison with such global impact.”

The follow-up

A follow-up study is planned to model the extent of coastal inundation worldwide, Arbic said. That study will be led by Vasily Titov of the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Lab, who is a co-author of the AGU Advances paper.

In addition to Range, Arbic, Moore, Johnson and Titov, the study authors are Alistair Adcroft of Princeton University, Joseph Ansong of the University of Ghana, Christopher Hollis of Victoria University of Wellington, Jeroen Ritsema of the University of Michigan,

Christopher Scotese of the PALEOMAP Project, and He Wang of NOAA’s Geophysical Fluid Dynamics Laboratory and the University Corporation for Atmospheric Research.

Funding was provided by the National Science Foundation and the University of Michigan Associate Professor Support Fund, which is supported by the Margaret and Herman Sokol Faculty Awards. The MOM6 simulations were carried out on the Flux supercomputer provided by the University of Michigan Advanced Research Computing Technical Services.

Study: The Chicxulub Impact Produced a Powerful Global Tsunami

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Issue 89 - October 2022

Seasonal Change in Antarctic Ice Sheet Movement Observed for The First Time

By The University of Cambridge

Some estimates of Antarctica’s total contribution to sea-level rise may be over- or underestimated, after researchers detected a previously unknown source of ice loss variability.

The researchers, from the University of Cambridge and Austrian engineering company ENVEO, identified distinct, seasonal movements in the flow of land-based ice draining into George VI Ice Shelf – a floating platform of ice roughly the size of Wales – on the Antarctic Peninsula.

Using imagery from the Copernicus/European Space Agency Sentinel-1 satellites, the researchers found that the glaciers feeding the ice shelf speed up by approximately 15% during the Antarctic summer. This is the first time that such seasonal cycles have been detected on land ice flowing into ice shelves in Antarctica. The results are reported in the journal The Cryosphere.

While it is not unusual for ice flow in Arctic and Alpine regions to speed up during summer, scientists had previously assumed that ice in Antarctica was not subject to the same seasonal movements, especially where it flows into large ice shelves and where temperatures are below freezing for most of the year.

This assumption was also, in part, fuelled by a lack of imagery collected over the icy continent in the past. “Unlike the Greenland Ice Sheet, where a high quantity of data has allowed us to understand how the ice moves from season to season and year to year, we haven’t had comparable data coverage to look for such changes over Antarctica until recently,” said Karla Boxall from Cambridge’s Scott Polar Research Institute (SPRI), the study’s first author.

“Observations of ice-speed change in the Antarctic Peninsula have typically been measured over successive years, so we’ve been missing a lot of the finer detail about how flow varies from month to month throughout the year,” said co-author Dr Frazer Christie, also from SPRI.

Prior to the detailed records of ice speed made possible by the Sentinel-1 satellites, scientists wanting to study short-term variations in Antarctic-wide ice flow had to rely on information collected by optical satellites such as NASA’s Landsat 8.

“Optical measurements can only observe the Earth’s surface on cloud-free days during summer months,” said co-author Dr Thomas Nagler, ENVEO’s CEO. “But by using Sentinel-1 radar imagery, we were able to discover seasonal ice-flow change thanks to the ability of these satellites to monitor year-round and in all-weather conditions.”

Currently, the causes of this seasonal change are uncertain. It could be caused by surface meltwater reaching the base of the ice and acting like a lubricant, as is the case in Arctic and Alpine regions, or it could be due to relatively warm ocean water melting the ice from below, thinning the floating ice and allowing upstream glaciers to move faster.

“These seasonal cycles could be due to either mechanism, or a mixture of the two,” said Christie. “Detailed ocean and surface measurements will be required to understand fully why this seasonal change is occurring.”

The results imply that similar seasonal variability may exist at other, more vulnerable sites in Antarctica, such as the Pine Island and Thwaites glaciers in West Antarctica. “If true, these seasonal signatures may be uncaptured in some measurements of Antarctic ice-mass loss, with potentially important implications for global sea-level rise estimates,” said Boxall.

“It’s the first time this seasonal signal has been found on the Antarctic Ice Sheet, so the questions it raises regarding the possible presence and causes of seasonality elsewhere in Antarctica are really interesting,” said co-author Professor Ian Willis, also from SPRI. “We look forward to taking a closer look at, and shedding light on, these important questions.”

The research was supported in part by the Natural Environment Research Council (NERC), part of UK Research & Innovation (UKRI), the Prince Albert II of Monaco Foundation and the European Space Agency. Karla Boxall is a PhD student at Newnham College, Cambridge. Frazer Christie is an Associate of Jesus College, Cambridge. Ian Willis is a Fellow of St Catharine’s College, Cambridge.

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Issue 89 - October 2022

SEVENSEAS Travel Magazine – October 2022 – Issue 89

Feature Destination

Feature Destination: Nature and Its Healing Power

South Korea has designated and operated national parks to preserve the natural ecosystems and natural and cultural wonders. As the designation requirements are demanding, the national park is an assorted gift set of healing benefits that allow visitors to enjoy natural ecosystems, natural landscapes, and cultural wonders at once. Read more…

Ocean Conservancy Plastic Pollution Experts to Attend South Korea for Seventh International Marine Debris Conference

A delegation of ocean plastic pollution experts from NGO Ocean Conservancy will be leading or presenting at more than 15 events at the upcoming 7th International Marine Debris Conference (7IMDC), the world’s longest-running international conference dedicated to the issue of marine litter and plastic pollution. Read more…

Feature Destination: In the Yellow Sea, a Shining Example of Marine Protection

It has been more than 20 years since South Korea and China began a novel partnership to restore and protect the shallow body of salt water that lies between them: the Yellow Sea, a semi-enclosed marine area bracketed by the Chinese mainland and the Korean peninsula. Read more…

Newsroom

Seeking a Sustainable Trip to Europe? The Alentejo is One of the Most Sustainable Destinations in Europe for 2023

Sustainable travel is a word we are hearing a lot of these days. And, sustainable practices don’t just apply to the travel industry, they apply to all of us. We need to make smart choices, and not contribute to over tourism or factors that will have a negative impact on our planet. We all need to do our share. Read more…

Dinosaur-Killing Asteroid Triggered Global Tsunami That Scoured Seafloor Thousands of Miles from Impact Site

The miles-wide asteroid that struck Earth 66 million years ago wiped out nearly all the dinosaurs and roughly three-quarters of the planet’s plant and animal species. It also triggered a monstrous tsunami with mile-high waves that scoured the ocean floor thousands of miles from the impact site. Read more…

Tougher Measures Urgently Needed From The International Maritime Organisation To Curb Plastic Pellet Pollution

A new report by international wildlife conservation charity, Fauna & Flora International (FFI), highlights the disastrous impact of plastic pellet pollution on marine wildlife and calls for a more robust, regulatory approach from industry. Read more…

Madagascar Whale Shark Project Unveils New Project to Empower Conservationists to Protect The Ocean

The Madagascar Whale Shark Project is announcing a new way for ocean lovers to support its efforts to protect endangered whale sharks. The project has launched a donation-based Patreon page to enable followers to support its vital work through a monthly subscription. Read more…

‘Hydrogen Road Map’: The Lightest Element Can Play a Heavy-Duty Role in Michigan’s Clean-Energy Transition

Hydrogen, the most abundant and lightest element in the universe, can play a significant role in accelerating Michigan’s clean-energy transition away from fossil fuels in the coming decades, according to a new report released today by the University of Michigan and the Michigan Economic Development Corporation. Read more…

SAWFISH NEWS: Respect-Release-Report: Guidelines for Interactions with Endangered Sawfish in the United States

Sawfish are majestic marine animals that were once found in coastal waters of the United States from Texas to North Carolina. Unfortunately, decades of mortality in fisheries and the loss of important nursery habitats led to dramatic reductions in both their numbers and range. Read more…

Coral Reef Protection To Grow With The Green Fins Hub

Sustainable marine tourism is receiving a major boost with the launch of the Green Fins Hub, a global digital platform for diving and snorkelling operators worldwide. The industry-backed digital platform is expected. Read more….

Science Without Borders® Challenge Announcement for 2023

The Khaled bin Sultan Living Oceans Foundation is excited to announce that our Science Without Borders® Challenge is now open! This annual art contest inspires students from all over the world to be creative while learning about important ocean science and conservation issues. More info…

Second Historic Canoe Recovered from Wisconsin’s Lake Mendota

Wisconsin Historical Society maritime archaeologists, alongside partners from Wisconsin’s Native Nations, recovered a 3,000-year-old dugout canoe from Lake Mendota in Madison today, less than one year after their recovery of a 1,200-year-old canoe that drew international attention in November 2021. Read more…

Navigating the Environmental Impact of Eco-Tourism

Eco-tourism is an environmentally-friendly way to travel the world and see incredible sights. Usually, it involves visiting ecologically-sensitive areas that need protection from tourists and travelers. Read more…

The Team of Biologists from The University of Vienna Discovers The Old Genes Keep Sea Anemones Forever Young

Nematostella vectensis, 6 mm. SERC, Rhode River, Edgewater, Ann Arundel County, MD

The genetic fingerprint of the sea anemone Nematostella vectensis shows that the members of this evolutionarily very old animal phylum use the same gene cascades for the differentiation of neuronal cell types as more complex organisms. Read more…

Seasonal Change in Antarctic Ice Sheet Movement Observed for The First Time

Some estimates of Antarctica’s total contribution to sea-level rise may be over- or underestimated, after researchers detected a previously unknown source of ice loss variability. Read more…

SEVENSEAS Beach Cleanups

In August 2022 CleanUp, we picked up over 80 kilogram of plastic, pieces of glasses, tractor tyre, and fishing nets from the beach in Krabi, Long Beach or Pan Beach. Of course, we would not be able to do it without your support. You can make a tax-deductible donation here to keep our publications and Thailand Cleanup Project afloat.

You can either make a direct financial contribution to SEVENSEAS Media through The Ocean Foundation website or connect us with potential donors by sending an email to Giacomo Abrusci, our Editor-in-Chief.

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Signing up for the free Weekly Newsletter & Jobs List will get you a round-up of upcoming events, webinars, meetings, reports, funding opportunities, photos of the week, and recent postings to the jobs list.

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Since 2004, SEVENSEAS Media has fostered an informal and non-partisan platform to promote understanding of key issues and challenges while building partnerships across an increasingly diverse group of marine conservation professionals and students.

Our mission is to promote communication and build partnerships across the global marine community and to identify and address gaps in the community’s work. SEVENSEAS Media achieves this through multimedia promotion and partnerships. The community consists of a diverse and growing group of participants, including non-governmental organizations, government agencies, foundations, bilateral and multilateral agencies, fellowship programs, independent consultants, and academia/students.

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Feature Destination

Feature Destination: In the Yellow Sea, a Shining Example of Marine Protection

The Yellow Sea’s amber-tinged waters and coastlines teem with 1,600 different species of fauna – from dugongs and sea turtles to flounders and rockfish. The land around the sea also teems with humanity. More than 600 million people, or 10 percent of the global population, live on or near its shores and rely on its health for food and income.

A generation ago, it became increasingly clear that the rapid economic development of the surrounding region was placing a heavy strain on this fragile and valuable environment.

Over-fishing and pollution from industry, agriculture, and housing had depleted fish stocks, while many of the region’s tidal mudflats, key feeding grounds for migratory birds, had been lost to coastal reclamation. Biodiversity was also threatened by invasive species and ecosystem changes such as algal blooms and nutrient contamination.

To counterbalance these threats, the governments of China and the Republic of Korea began working with the Global Environment Facility and UN Development Programme (UNDP) in the mid-1990s to lay plans for the Yellow Sea Large Marine Ecosystem Project (YSLME).

A new report published by the YSLME project and available through the GEF’s International Waters knowledge-sharing platform IW:Learn details the array of innovative solutions introduced since the start of the Yellow Sea Large Marine Ecosystem project.

These have included the ranching of key marine species for reintroduction, government-led schemes to buy back fishing vessels and lessen pressure on stocks, enhanced monitoring of pollutants, and curbs on coastal reclamation and commercial fishing.

Harvesting kelp in Dongchu Village. Photo credit: Yitao Zhang

These initiatives have benefited the region in many ways: restoring marine forests around the picturesque island of Jeju to stem the spread of barren ground near the coast, helping to protect the tiny and critically endangered spoon-billed sandpiper, and encouraging cooperation with other countries to preserve the habitat of the spotted seal, one of the region’s flagship species.

The first phase of the project initially focused on helping the countries conduct a Transboundary Diagnostic Analysis (TDA) of the Yellow Sea to pinpoint the most pressing environmental perils and their immediate and root causes.

This analysis formed the technical basis for the bilateral talks between China and the Republic of Korea that led up to the preparation and ministerial adoption of an initial Strategic Action Programme. Approved by both countries in 2009, the Programme set out pledges from the partners to take steps to reduce environmental pressures, such as fishing limits, improved management of sea and coastal areas, and pollution reduction targets.

A second phase of the project began in 2014 and closed in 2021. This phase resulted in the preparation of a new YSLME Strategic Action Programme for 2020-2030 and an updated TDA to guide and inform efforts.

A critical part of the initiative was the sharing of successes, challenges, and lessons, so other regions could learn from the marine restoration efforts of China and the Republic of Korea.

“Thanks to the results, experience and lessons from the Yellow Sea Large Marine Ecosystem Project, countries around the world are better equipped to put in place good practices on sustainable fisheries and aquaculture that can protect the ocean’s health and propel sustainable blue development,” said GEF CEO and Chairperson Carlos Manuel Rodriguez. “It is a shining example of what can be achieved through cooperation on shared marine resources.”

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