Tag Archives: #ocean

Oceanographers Have an Explanation For the Arctic’s Puzzling Ocean Turbulence (Earth Science / Oceanography)

New study suggests waters will become more turbulent as Arctic loses summertime ice.

Eddies are often seen as the weather of the ocean. Like large-scale circulations in the atmosphere, eddies swirl through the ocean as slow-moving sea cyclones, sweeping up nutrients and heat, and transporting them around the world.

MIT oceanographers have proposed an explanation for the Arctic’s puzzling ocean turbulence. ©MIT

In most oceans, eddies are observed at every depth and are stronger at the surface. But since the 1970s, researchers have observed a peculiar pattern in the Arctic: In the summer, Arctic eddies resemble their counterparts in other oceans, popping up throughout the water column. However, with the return of winter ice, Arctic waters go quiet, and eddies are nowhere to be found in the first 50 meters beneath the ice. Meanwhile, deeper layers continue to stir up eddies, unaffected by the abrupt change in shallower waters.

This seasonal turn in Arctic eddy activity has puzzled scientists for decades. Now an MIT team has an explanation. In a paper published today in the Journal of Physical Oceanography, the researchers show that the main ingredients for driving eddy behavior in the Arctic are ice friction and ocean stratification.

By modeling the physics of the ocean, they found that wintertime ice acts as a frictional brake, slowing surface waters and preventing them from speeding into turbulent eddies. This effect only goes so deep; between 50 and 300 meters deep, the researchers found, the ocean’s salty, denser layers act to insulate water from frictional effects, allowing eddies to swirl year-round.

The results highlight a new connection between eddy activity, Arctic ice, and ocean stratification, that can now be factored into climate models to produce more accurate predictions of Arctic evolution with climate change.

“As the Arctic warms up, this dissipation mechanism for eddies, i.e. the presence of ice, will go away, because the ice won’t be there in summer and will be more mobile in the winter,” says John Marshall, professor of oceanography at MIT. “So what we expect to see moving into the future is an Arctic that is much more vigorously unstable, and that has implications for the large-scale dynamics of the Arctic system.”

Marshall’s co-authors on the paper include lead author Gianluca Meneghello, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences, along with Camille Lique, Pal Erik Isachsen, Edward Doddridge, Jean-Michel Campin, Healther Regan, and Claude Talandier.

This image shows the activity of eddies simulated in the Arctic Ocean. The left panel shows seasonal changes in eddy activity at the surface of the ocean, compared to the right panel, where eddy behavior is unaffected by the seasons, and remains the same at deeper levels of the ocean. Courtesy of: Gianluca Meneghello

Beneath the surface

For their study, the researchers assembled data on Arctic ocean activity that were made available by the Woods Hole Oceanographic Institution. The data were collected between 2003 and 2018, from sensors measuring the velocity of the water at different depths throughout the water column.

The team averaged the data to produce a time series to produce a typical year of the Arctic Ocean’s velocities with depth. From these observations, a clear seasonal trend emerged: During the summer months with very little ice cover, they saw high velocities and more eddy activity at all depths of the ocean. In the winter, as ice grew and increased in thickness, shallow waters ground to a halt, and eddies disappeared, whereas deeper waters continued to show high-velocity activity.

“In most of the ocean, these eddies extend all the way to the surface,” Marshall says. “But in the Arctic winter, we find that eddies are kind of living beneath the surface, like submarines hanging out at depth, and they don’t get all the way up to the surface.”

To see what might be causing this curious seasonal change in eddy activity, the researchers carried out a “baroclinic instability analysis.” This model uses a set of equations describing the physics of the ocean, and determines how instabilities, such as weather systems in the atmosphere and eddies in the ocean, evolve under given conditions.

An icy rub

The researchers plugged various conditions into the model, and for each condition they introduced small perturbations similar to ripples from surface winds or a passing boat, at various ocean depths. They then ran the model forward to see whether the perturbations would evolve into larger, faster eddies.

The researchers found that when they plugged in both the frictional effect of sea ice and the effect of stratification, as in the varying density layers of the Arctic waters, the model produced water velocities that matched what the researchers initially saw in actual observations. That is, they saw that without friction from ice, eddies formed freely at all ocean depths. With increasing friction and ice thickness, waters slowed and eddies disappeared in the ocean’s first 50 meters. Below this boundary, where the water’s density, i.e. its stratification, changes dramatically, eddies continued to swirl.

When they plugged in other initial conditions, such as a stratification that was less representative of the real Arctic ocean, the model’s results were a weaker match with observations.

“We’re the first to put forward a simple explanation for what we’re seeing, which is that subsurface eddies remain vigorous all year round, and surface eddies, as soon as ice is around, get rubbed out because of frictional effects,” Marshall explains.

Now that they have confirmed that ice friction and stratification have an effect on Arctic eddies, the researchers speculate that this relationship will have a large impact on shaping the Arctic in the next few decades. There have been other studies showing that summertime Arctic ice, already receding faster year by year, will completely disappear by the year 2050. With less ice, waters will be free to swirl up into eddies, at the surface and at depth. Increased eddy activity in the summer could bring in heat from other parts of the world, further warming the Arctic.

At the same time, the wintertime Arctic will be ice covered for the foreseeable future, notes Meneghello. Whether a warming Arctic will result in more ocean turbulence throughout the year or in a stronger variability over the seasons will depend on sea ice’s strength.

Regardless, “if we move into a world where there is no ice at all in the summer and weaker ice during winter, the eddy activity will increase,” Meneghello says. “That has important implications for things moving around in the water, like tracers and nutrients and heat, and feedback on the ice itself.”

This research is supported, in part, by the National Science Foundation.

Provided by MIT

What Caused the Ice Ages? Tiny Ocean Fossils Offer Key Evidence (Biology)

The ocean’s role in past atmospheric carbon dioxide change comes into focus.

The last million years of Earth history have been characterized by frequent “glacial-interglacial cycles,” large swings in climate that are linked to the growing and shrinking of massive, continent-spanning ice sheets. These cycles are triggered by subtle oscillations in Earth’s orbit and rotation, but the orbital oscillations are too subtle to explain the large changes in climate.

Since the discovery that atmospheric carbon dioxide (CO2) concentrations were lower during past ice ages, the cause has been a mystery. Now, scientists have discovered that a weakening in upwelling in the Antarctic Ocean, the ocean around Antarctica, kept more CO2 in the deep ocean during the ice ages. This diatom species, Fragilariopsis kerguelensis, photographed both alive (left) and fossilized (right), is a floating algae that is abundant in the Antarctic Ocean and was the major species in the samples collected for this study. Nitrogen isotopes in their shells vary with the amount of unused nitrogen in the surface water. Researchers used that to trace nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods. Image of live diatom by Philipp Assmy (Norwegian Polar Institute) and Marina Montresor (Stazione Zoologica Anton Dohrn); fossilized diatoms (c) Michael Kloster, Alfred-Wegener-Institute

“The cause of the ice ages is one of the great unsolved problems in the geosciences,” said Daniel Sigman, the Dusenbury Professor of Geological and Geophysical Sciences. “Explaining this dominant climate phenomenon will improve our ability to predict future climate change.”

In the 1970s, scientists discovered that the concentration of the atmospheric greenhouse gas carbon dioxide (CO2) was about 30% lower during the ice ages. That prompted theories that the decrease in atmospheric CO2 levels is a key ingredient in the glacial cycles, but the causes of the CO2 change remained unknown. Some data suggested that, during ice ages, CO2 was trapped in the deep ocean, but the reason for this was debated.

Now, an international collaboration led by scientists from Princeton University and the Max Planck Institute for Chemistry (MPIC) have found evidence indicating that during ice ages, changes in the surface waters of the Antarctic Ocean worked to store more CO2 in the deep ocean. Using sediment cores from the Antarctic Ocean, the researchers generated detailed records of the chemical composition of organic matter trapped in the fossils of diatoms — floating algae that grew in the surface waters, then died and sank to the sea floor. Their measurements provide evidence for systematic reductions in wind-driven upwelling in the Antarctic Ocean during the ice ages. The research appears in the current issue of the journal Science.

For decades, researchers have known that the growth and sinking of marine algae pumps CO2 deep into the ocean, a process often referred to as the “biological pump.” The biological pump is driven mostly by the tropical, subtropical and temperate oceans and is inefficient closer to the poles, where CO2 is vented back to the atmosphere by the rapid exposure of deep waters to the surface. The worst offender is the Antarctic Ocean: the strong eastward winds encircling the Antarctic continent pull CO2-rich deep water up to the surface, “leaking” CO2 to the atmosphere.

This diatom species, Fragilariopsis kerguelensis, is a floating algae that is abundant in the Antarctic Ocean and was the major species in the samples collected for the study by Princeton University and the Max Planck Institute for Chemistry. These microscopic organisms live near the sea surface, then die and sink to the sea floor. The nitrogen isotopes in their shells vary with the amount of unused nitrogen in the surface water. The researchers used that to trace nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods. ©Philipp Assmy (Norwegian Polar Institute) and Marina Montresor (Stazione Zoologica Anton Dohrn)

The potential for a reduction in wind-driven upwelling to keep more CO2 in the ocean, and thus to explain the ice age atmospheric CO2 drawdown, has also been recognized for decades. Until now, however, scientists have lacked a way to unambiguously test for such a change.

The Princeton-MPIC collaboration has developed such an approach, using tiny diatoms. Diatoms are floating algae that grow abundantly in Antarctic surface waters, and their silica shells accumulate in deep sea sediment. The nitrogen isotopes in diatoms’ shells vary with the amount of unused nitrogen in the surface water. The Princeton-MPIC team measured the nitrogen isotope ratios of the trace organic matter trapped in the mineral walls of these fossils, which revealed the evolution of nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods.

“Analysis of the nitrogen isotopes trapped in fossils like diatoms reveals the surface nitrogen concentration in the past,” said Ellen Ai, first author of the study and a Princeton graduate student working with Sigman and with the groups of Alfredo Martínez-García and Gerald Haug at MPIC. “Deep water has high concentrations of the nitrogen that algae rely on. The more upwelling that occurs in the Antarctic, the higher the nitrogen concentration in the surface water. So our results also allowed us to reconstruct Antarctic upwelling changes.”

The data were made more powerful by a new approach for dating the Antarctic sediments. Surface water temperature change was reconstructed in the sediment cores and compared with Antarctic ice core records of air temperature.

This diatom species, Fragilariopsis kerguelensis, is a floating algae that is abundant in the Antarctic Ocean and was the major species in the samples collected for the study by Princeton University and the Max Planck Institute for Chemistry. These microscopic organisms live near the sea surface, then die and sink to the sea floor. The nitrogen isotopes in their shells vary with the amount of unused nitrogen in the surface water. The researchers used that to trace nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods. (c) Michael Kloster, Alfred-Wegener-Institute

“This allowed us to connect many features in the diatom nitrogen record to coincident climate and ocean changes from across the globe,” said Martínez-García. “In particular, we are now able to pin down the timing of upwelling decline, when climate starts to cool, as well as to connect upwelling changes in the Antarctic with the fast climate oscillations during ice ages.”

This more precise timing allowed the researchers to home in on the winds as the key driver of the upwelling changes.

The new findings also allowed the researchers to disentangle how the changes in Antarctic upwelling and atmospheric CO2 are linked to the orbital triggers of the glacial cycles, bringing scientists a step closer to a complete theory for the origin of the ice ages.

“Our findings show that upwelling-driven atmospheric CO2 change was central to the cycles, but not always in the way that many of us had assumed,” said Sigman. “For example, rather than accelerating the descent into the ice ages, Antarctic upwelling caused CO2 changes that prolonged the warmest climates.”

Their findings also have implications for predicting how the ocean will respond to global warming. Computer models have yielded ambiguous results on the sensitivity of polar winds to climate change. The researchers’ observation of a major intensification in wind-driven upwelling in the Antarctic Ocean during warm periods of the past suggests that upwelling will also strengthen under global warming. Stronger Antarctic upwelling is likely to accelerate the ocean’s absorption of heat from ongoing global warming, while also impacting the biological conditions of the Antarctic Ocean and the ice on Antarctica.

“The new findings suggest that the atmosphere and ocean around Antarctica will change greatly in the coming century,” said Ai. “However, because the CO2 from fossil fuel burning is unique to the current times, more work is needed to understand how Antarctic Ocean changes will affect the rate at which the ocean absorbs this CO2.”

“Southern Ocean upwelling, Earth’s obliquity, and glacial-interglacial atmospheric CO2 change” by Xuyuan Ellen Ai, Anja S. Studer, Daniel M. Sigman, Alfredo Martínez-García, François Fripiat, Lena M. Thöle, Elisabeth Michel, Julia Gottschalk, Laura Arnold, Simone Moretti, Mareike Schmitt, Sergey Oleynik, Samuel L. Jaccard and Gerald H. Haug appears in the Dec. 11 issue of Science (DOI: 10.1126/science.abd2115). The research was supported by the National Science Foundation (grant PLR-1401489 to D.M.S.), ExxonMobil through the Andlinger Center for Energy and the Environment at Princeton University, the Swiss National Science Foundation (grant PBEZP2_145695 to A.S.S. and grants PP00P2_144811 and PP00P2_172915 to S.L.J.), a Global Research Fellowship from the German Research Foundation (DFG grant GO 2294/2-1 to J.G.), and the Max Planck Society. Other Princeton connections: Anja Studer and Francois Fripiat were both postdoctoral researchers in Sigman’s lab, and Sergey Oleynik is the isotope lab manager for Princeton’s Department of Geosciences.

Provided by Princeton University

Satellite Tag Tracks Activity Levels of Highly Migratory Species Across the Vast Ocean (Biology)

New technology helps scientists better understand how highly migratory species are responding to a changing ocean.

Scientists at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science and Wildlife Computers, Inc. today announced the release of a new activity data product application for marine animal tracking. The technology is designed to remotely track and transmit data gathered on an animal’s activity levels over several months along with the temperatures and depths they experienced.

Cobia (Rachycentron canadum) equipped with ATS enabled PSAT during captive validation trials. Photo: Matt Bernanke – Sharktagging.com

Determining if and how marine animals change their activity levels in response to varying environmental conditions like temperature is important for understanding and predicting their responses to global warming and other environmental changes.

“The new feature available on the Wildlife Computers MiniPAT pop-up tag has an integrated accelerometer for measuring activity, and its onboard software computes a summarized value of overall activity level, which can be transmitted to satellites,” said Rachel Skubel, the study’s lead author and a Doctoral student at UM’s Abess Center for Ecosystem Science & Policy. “The Activity Time Series (ATS) data product allows us to determine when the tagged animal is switching from slow to fast swimming and vice versa.”

Wide-ranging ocean species, such as sharks, tunas, and billfish, lead complex lives hidden under the ocean surface. This makes studying activity levels in these species very challenging for scientists. While some tags have integrated accelerometers capable of measuring animal activity levels, the amount of raw data generated is generally too large to transmit via satellite, which required scientists to somehow retrieve the tags and download the accelerometer data. This has been a major limitation for gathering key data on how these species use their environment.

“Along with changes in activity level, the tag also collects and transmits data on the animal’s swimming depth and the temperatures they encounter with a user-programmable resolution,” said Kenady Wilson, Ph.D. research scientist, Wildlife Computers and a co-author of the study. “These data are transmitted via our MiniPAT (pop-up archival transmitting tag) with a tracking period of up to three months.”

This was truly a collaborative effort with the University of Miami and professor Hammerschlag’s team,” said Melinda Holland, CEO of Wildlife Computers. “This project demonstrates exactly what we do with the research community–design, develop, test, and deliver a tag that meets the project’s goals and objectives.”

To test the new ATS technology, researchers attached MiniPAT tags to cobia (Rachycentron canadum) housed at the University of Miami’s Experimental Fish Hatchery. Using cameras to record the actual behaviors of the tagged cobia, researchers evaluated how changes in activity levels measured and transmitted by the ATS satellite tags matched the actual activity levels of the cobia recorded on camera. To see how well the tag performed in the wild, the team attached MiniPAT tags enabled with the ATS data product to sandbar sharks. After one month, the tags popped off as programed and successfully transmitted the sharks’ activity data along with their environmental conditions and locations.

“The ability to now remotely track how animals are behaviorally responding to changes in environmental conditions over several months and across vast expanses of open ocean really opens up a lot of new research opportunities” said Neil Hammerschlag, research associate professor at the UM Rosenstiel School of Marine & Atmospheric Science and UM Abess Center for Ecosystem Science & Policy. “This is especially important for understanding if and how these species respond to climate change”

The study, titled “A scalable, satellite-transmitted data product for monitoring high-activity events in mobile aquatic animals” was published on 22 November 2020 in the journal Animal Biotelemetry.

The study’s authors include: Rachel Skubel, Daniel Benetti and Neil Hammerschlag at the University of Miami Rosenstiel School of Marine and Atmospheric Science, Kenady Wilson at Wildlife Computers, Yannis Papastamatiou at Florida International University, and Hannah Verkampp and James Sulikowski at Arizona State University.

Rachel Skubel is supported by an NSERC PGS-D scholarship from the Government of Canada, a UM Fellowship from the University of Miami, and a Guy Harvey Scholarship from Florida Sea Grant and the Guy Harvey Ocean Foundation. This study was supported by a University of Miami Provost Grant.

Reference: Skubel, R.A., Wilson, K., Papastamatiou, Y.P. et al. A scalable, satellite-transmitted data product for monitoring high-activity events in mobile aquatic animals. Anim Biotelemetry 8, 34 (2020). https://animalbiotelemetry.biomedcentral.com/articles/10.1186/s40317-020-00220-0 https://doi.org/10.1186/s40317-020-00220-0

Provided by University of Miami’s Rosenstiel School

Researchers Discover Life in Deep Ocean Sediments At Or Above Water’s Boiling Point (Oceanography)

3 URI researchers part of international research team.

An international research team that included three scientists from the University of Rhode Island’s Graduate School of Oceanography has discovered single-celled microorganisms in a location where they didn’t expect to find them.

Microbial cells in sediment; microbial cells are green, sediment particles are yellow. (Image courtesy of JAMSTEC)

“Water boils on the (Earth’s) surface at 100 degrees Celsius, and we found organisms living in sediments at 120 degrees Celsius,” said URI Professor of Oceanography Arthur Spivack, who led the geochemistry efforts of the 2016 expedition organized by the Japan Agency for Marine-Earth Science and Technology and Germany’s MARUM-Center for Marine and Environmental Sciences at the University of Bremen. The study was carried out as part of the work of Expedition 370 of the International Ocean Discovery Program.

The research results from a two-month-long expedition in 2016 will be published today in the journal Science.

The news follows an announcement in October that microbial diversity below the seafloor is as rich as on Earth’s surface. Researchers on that project from the Japan marine-earth science group, Bremen University, the University of Hyogo, University of Kochi and University of Rhode Island, discovered 40,000 different types of microorganisms from core samples from 40 sites around the globe.

The research published in Science today focused on the Nankai Trough off the coast of Japan, where the deep-sea scientific vessel, Chinkyu, drilled a hole 1,180 meters deep to reach sediment at 120 degrees Celsius. The leader of the study is Professor Kai-Uwe Hinrichs of MARUM.

Spivack, who was joined by recent Ph.D. graduates, Kira Homola and Justine Sauvage, on the URI team, said one way to identify life is to look for evidence of metabolism.

“We found chemical evidence of the organisms’ use of organic material in the sediment that allows them to survive,” Spivack said. The URI team also developed a model for the temperature regime of the site.

“This research tells us that deep sediment is habitable in places that we did think possible,” he added.

While this is exciting news on its own, Spivack said the research could point to the possibility of life in harsh environments on other planets.

According to the study, sediments that lie deep below the ocean floor are harsh habitats. Temperature and pressure steadily increase with depth, while the energy supply becomes increasingly scarce. It has only been known for about 30 years that, in spite of these conditions, microorganisms do inhabit the seabed at depths of several kilometers. The deep biosphere is still not well understood, and this brings up fundamental questions: Where are the limits of life, and what factors determine them? To study how high temperatures affect life in the low-energy deep biosphere over the long-term, extensive deep-sea drilling is necessary.

“Only a few scientific drilling sites have yet reached depths where temperatures in the sediments are greater than 30 degrees Celsius,” explains study leader Hinrichs of MARUM. “The goal of the T-Limit Expedition, therefore, was to drill a thousand-meter deep hole into sediments with a temperature of up to 120 degrees Celsius – and we succeeded.”

Like the search for life in outer space, determining the limits of life on the Earth is fraught with great technological challenges, the research study says.

“Surprisingly, the microbial population density collapsed at a temperature of only about 45 degrees,” says co-chief scientist Fumio Inagaki of JAMSTEC. “It is fascinating – in the high-temperature ocean floor, there are broad depth intervals that are almost lifeless. But then we were able to detect cells and microbial activity again in deeper, even hotter zones – up to a temperature of 120 degrees.”

Spivack said the project was like going back to his roots, as he and David Smith, professor of oceanography and associate dean of URI’s oceanography school, where they were involved in a drilling expedition at the same site about 20 years ago, an expedition that helped initiate the study of the deeply buried marine biosphere.

As for the current project, Spivack said studies will continue on the samples the team collected. “The technology to examine samples collected from the moon took several years to be developed, and the same will be true for these samples from deep in the ocean sediments. We are developing the technology now to continue our research.”

References: Verena B. Heuer, Fumio Inagaki, Yuki Morono, Yusuke Kubo, Arthur J. Spivack, Bernhard Viehweger, Tina Treude, Felix Beulig, Florence Schubotz, Satoshi Tonai, Stephen A. Bowden, Margaret Cramm, Susann Henkel, Takehiro Hirose, Kira Homola, Tatsuhiko Hoshino, Akira Ijiri, Hiroyuki Imachi, Nana Kamiya, Masanori Kaneko, Lorenzo Lagostina, Hayley Manners, Harry-Luke McClelland, Kyle Metcalfe, Natsumi Okutsu, Donald Pan, Maija J. Raudsepp, Justine Sauvage, Man-Yin Tsang, David T. Wang, Emily Whitaker, Yuzuru Yamamoto, Kiho Yang, Lena Maeda, Rishi R. Adhikari, Clemens Glombitza, Yohei Hamada, Jens Kallmeyer, Jenny Wendt, Lars Wörmer, Yasuhiro Yamada, Masataka Kinoshita, Kai-Uwe Hinrichs, “Temperature limits to deep subseafloor life in the Nankai Trough subduction zone”, Science 04 Dec 2020: Vol. 370, Issue 6521, pp. 1230-1234. https://science.sciencemag.org/content/370/6521/1230
DOI: 10.1126/science.abd7934

Provided by University of Rhode Island

Could Kelp Help Relieve Ocean Acidification? (Earth Science)

Ethereal, swaying pillars of brown kelp along California’s coasts grow up through the water column, culminating in a dense surface canopy of thick fronds that provide homes and refuge for numerous marine creatures. There’s speculation that these giant algae may protect coastal ecosystems by helping alleviate acidification caused by too much atmospheric carbon being absorbed by the seas.

Aerial drone photo of the kelp forest canopy on the protected side of Cabrillo Point. Hopkins Marine Station is on the point in the upper left corner. Image credit: Heidi Hirsh

A new on-site, interdisciplinary analysis of giant kelp in Monterey Bay off the coast of California sought to further investigate kelp’s acidification mitigation potential. “We talk about kelp forests protecting the coastal environment from ocean acidification, but under what circumstances is that true and to what extent?” said study team member Heidi Hirsh, a PhD student at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “These kinds of questions are important to investigate before trying to implement this as an ocean acidification mitigation strategy.”

The team’s findings, published on Oct. 22 in the journal JGR Oceans, show that near the ocean’s surface, the water’s pH was slightly higher, or less acidic, suggesting the kelp canopy does reduce acidity. However, those effects did not extend to the ocean floor, where sensitive cold-water corals, urchins and shellfish dwell and the most acidification has occurred.

“One of the main takeaways for me is the limitation of the potential benefits from kelp productivity,” said Hirsh, the lead author on the study.

Why kelp?

Kelp is an ecologically and economically important foundation species in California, where forests line nutrient-rich, rocky bottom coasts. One of the detrimental impacts of increased carbon in the atmosphere is its subsequent absorption by the planet’s oceans, which causes acidification – a chemical imbalance that can negatively impact the overall health of marine ecosystems, including animals people depend on for food.

Kelp has been targeted as a potentially ameliorating species in part because of its speedy growth – up to 5 inches per day – during which it undergoes a large amount of photosynthesis that produces oxygen and removes carbon dioxide from the water. In Monterey Bay, the effects of giant kelp are also influenced by seasonal upwelling, when deep, nutrient-rich, highly acidic water from the Pacific is pulled toward the surface of the bay.

“It’s this very complicated story of disentangling where the benefit is coming from – if there is a benefit – and assessing it on a site-by-site basis, because the conditions that we observe in southern Monterey Bay may not apply to other kelp forests,” Hirsh said.

Giant kelp (Macrocystis pyrifera) surface canopy in Monterey Bay, California. (Image credit: Christy Varga)

The researchers set up operations at Stanford’s Hopkins Marine Station, a marine laboratory in Pacific Grove, California, and collected data offshore from the facility in a 300-foot-wide kelp forest. Co-author Yuichiro Takeshita of the Monterey Bay Aquarium Research Institute (MBARI) provided pH sensors that were distributed throughout the area to understand chemical and physical changes in conjunction with water sampling.

“We are moving beyond just collecting more chemistry data and actually getting at what’s behind the patterns in that data,” said co-principal investigator Kerry Nickols, an assistant professor at California State University, Northridge. “If we didn’t look at the water properties in terms of how they’re changing and the differences between the top and the bottom of the kelp forests, we really wouldn’t understand what’s going on.”

With the new high-resolution, vertical measurements of pH, dissolved oxygen, salinity and temperature, the researchers were able to distinguish patterns in the seawater chemistry around the kelp forest. At night, when they expected to see more acidic water, the water was actually less acidic relative to daytime measurements – a result they hypothesize was caused by the upwelling of acidic, low oxygen water during the day.

“It was wild to see the pH climb during the night when we were expecting increased acidity as a function of kelp respiration,” Hirsh said. “That was an early indicator of how important the physical environment was for driving the local biogeochemical signal.”

Designing a nature-based solution

While this project looked at kelp’s potential to change the local environment on a short-term basis, it also opens the doors to understanding long-term impacts, like the ability to cultivate “blue carbon,” the underwater sequestration of carbon dioxide.

“One of the reasons for doing this is to enable the design of kelp forests that might be considered as a blue carbon option,” said co-author Stephen Monismith, the Obayashi Professor in the School of Engineering. “Understanding exactly how kelp works mechanistically and quantitatively is really important.”

Although the kelp forests’ mitigation potential in the canopy didn’t reach the sensitive organisms on the sea floor, the researchers did find an overall less acidic environment within the kelp forest compared to outside of it. The organisms that live in the canopy or could move into it are most likely to benefit from kelp’s local acidification relief, they write.

A model for future study

The research also serves as a model for future investigation about the ocean as a three-dimensional, fluid habitat, according to the co-authors.

“The current knowledge set is pretty large, but it tends to be disciplinary – it’s pretty rare bringing all these elements together to study a complex coastal system,” said co-PI Rob Dunbar, the W.M. Keck Professor at Stanford Earth. “In a way, our project was kind of a model for how a synthetic study pulling together many different fields could be done.”

Monismith is also a member of Bio-X and an affiliate of the Stanford Woods Institute for the Environment. Dunbar is also a member of Bio-X and a senior fellow with Stanford Woods Institute for the Environment. Co-authors on the study include Sarah Traiger from California State University, Northridge and David Mucciarone from Stanford’s Department of Earth System Science.

References: Hirsh, H. K., Nickols, K. J., Takeshita, Y., Traiger, S. B., Mucciarone, D. A., Monismith, S., & Dunbar, R. B. (2020). Drivers of biogeochemical variability in a central California kelp forest: Implications for local amelioration of ocean acidification. Journal of Geophysical Research: Oceans, 125, e2020JC016320. Accepted Author Manuscript. https://doi.org/10.1029/2020JC016320

Provided by Stanford University

Did We Find Water World In Another Planetary System? (Planetary Science)

An international team led by the Center for Astrobiology (CAB, CSIC-INTA) has studied in detail the LHS1140 planetary system. The results confirm the existence of two planets and suggest the presence of two more. One of the planets, LHS1140 b, located in the habitable zone, appears to have a large ocean of liquid water, making it an ideal target to search for biomarkers.

Artistic illustration of the planet LHS 1140 b and its parent star. Credit: J. Lillo-Box.

LHS1140 is a planetary system located in the constellation of Cetus, about 41 light years from Earth, in which two planets were already known, LHS1140 b and LHS1140 c, the first of them located in the so-called habitable zone of its star, a red dwarf five times smaller than our Sun. The closest planet, LHS1140 c, orbits the star every 3.8 days, while LHS1140 b does so every 24.7 days.

This study, led by researchers from the Center for Astrobiology (CAB, CSIC-INTA) and published in the journal Astronomy & Astrophysics, has been carried out using the data obtained with the state-of-the-art instrument ESPRESSO, installed in the Very Large Telescope of the European Southern Observatory in Chile, and with the NASA’s space-based observatory TESS. The data have served to obtain very precise values of the masses and radii of both planets (6.5 Earth masses and 1.7 Earth radii for LHS1140 b; and 1.8 Earth masses and 1.3 Earth radii for LHS1140 c) allowing the authors to calculate not only their density (exactly the same as that of the Earth on both planets), but also characterize their internal composition (that is, the distribution of the core, mantle and crust of the planets, as well as the amount of liquid water they can have). In the case of LHS1140 b, the calculations point to a surface covered by an ocean of liquid water. Jorge Lillo-Box, CAB researcher and lead author of the study, points out that “it is the habitable zone planet where the potential amount of liquid water present has been more precisely quantified, which makes LHS1140 b one of the best planets to the search for biomarkers ”.

The high precision of the data has also allowed the researchers to find another potential planet in the system, LHS1140 d, with a mass of 4.8 Earth masses and an orbital period of 78.9 days. This planet is located slightly further from the star’s habitable zone and has a composition on the frontier between rocky and gaseous. Finally, and as part of the TROY project (www.troy-project.com) a detailed study of the data was carried out in search for co-orbital or exotrojan companions, this is planets sharing the same orbital path. The study suggests that the innermost planet (LHS1140 c) could have one of these co-orbital partners. It is one of the first exotrojan candidates discovered so far, but more detailed study and additional observations are needed to confirm this exotic scenario.

“The LHS1140 planetary system is ideal on our path towards atmospheric characterization of rocky planets. The innermost planet must have a high content of water vapor, while the planet in the habitable zone must show very different atmospheric characteristics and perhaps allow the search for biomarkers such as ozone or methane”, says Lillo-Box.

The LHS1140 planetary system contains the type of planets that the KOBE experiment will look for, a legacy program of the Calar Alto Observatory (CAHA) of which Lillo-Box is the Principal Investigator, and that will search for planets in the habitable zone of stars slightly hotter than LHS1140, although cooler than our Sun. These stars offer a unique opportunity to search for life because, although their activity is much less than in colder stars, their zone of habitability is closer than in the solar-type stars. The program, which will begin in 2021 and end in 2023, will use the CARMENES instrument installed on the CAHA’s 3.5-meter telescope.

For David Barrado Navascués, CAB researcher and co-author of the study, “the LHS1140 planetary system should be a Rosetta stone for exoplanetary atmospheric studies. In this sense, the new James Webb Space Telescope, scheduled to launch in 2021, will play a fundamental role in these future studies, due to its size and instrumentation. Specifically, the Mid InfraRed Instrument (MIRI), developed by a European consortium in which the National Institute of Aerospace Technology (INTA) has a relevant participation, will be key to achieving this objective”.

References: J. Lillo Box et al., “Planetary system LHS 1140 revisited with ESPRESSO and TESS”, A&A 642, A121 (2020) link: https://www.aanda.org/articles/aa/full_html/2020/10/aa38922-20/aa38922-20.html

Provided by CSIC

Deep Sea Coral Time Machines Reveal Ancient CO2 Burps (Archeology)

The fossilised remains of ancient deep-sea corals may act as time machines providing new insights into the effect the ocean has on rising CO2 levels, according to new research carried out by the Universities of Bristol, St Andrews and Nanjing and published in Science Advances.

©University Of Bristol

Rising CO2 levels helped end the last ice age, but the cause of this CO2 rise has puzzled scientists for decades. Using geochemical fingerprinting of fossil corals, an international team of scientists has found new evidence that this CO2 rise was linked to extremely rapid changes in ocean circulation around Antarctica.

The team collected fossil remains of deep-sea corals that lived thousands of metres beneath the waves. By studying the radioactive decay of the tiny amounts of uranium found in these skeletons, they identified corals that grew at the end of the ice age around 15,000 years ago.

Further geochemical fingerprinting of these specimens – including measurements of radiocarbon – allowed the team to reconstruct changes in ocean circulation and compare them to changes in global climate at an unprecedented time resolution.

©University Of Bristol

Professor Laura Robinson, Professor of Geochemistry at Bristol’s School of Earth Sciences who led the research team, said: “The data show that deep ocean circulation can change surprisingly rapidly, and that this can rapidly release CO2 to the atmosphere.”

Dr James Rae at St Andrew’s School of Earth and Environmental Sciences, added: “The corals act as a time machine, allowing us to see changes in ocean circulation that happened thousands of years ago.

“They show that the ocean round Antarctica can suddenly switch its circulation to deliver burps of CO2 to the atmosphere.”

Scientists have suspected that the Southern Ocean played an important role in ending the last ice age and the team’s findings add weight to this idea.

Dr Tao Li of Nanjing University, lead author of the new study, said: “There is no doubt that Southern Ocean processes must have played a critical role in these rapid climate shifts and the fossil corals provide the only possible way to examine Southern Ocean processes on these timescales.”

©University Of Bristol

In another study published in Nature Geoscience this week the same team ruled out recent speculation that the global increase in CO2 at the end of the ice age may have been related to release of geological carbon from deep sea sediments.

Andrea Burke at St Andrew’s School of Earth and Environmental Sciences, added: “There have been some suggestions that reservoirs of carbon deep in marine mud might bubble up and add CO2 to the ocean and the atmosphere, but we found no evidence of this in our coral samples.”

Dr Tianyu Chen of Nanjing University said: “Our robust reconstructions of radiocarbon at intermediate depths yields powerful constraints on mixing between the deep and upper ocean, which is important for modelling changes in circulation and carbon cycle during the last ice age termination.

Dr James Rae added: “Although the rise in CO2 at the end of the ice age was dramatic in geological terms, the recent rise in CO2 due to human activity is much bigger and faster. What the climate system will do in response is pretty scary.”

References: (1) Tao Li, Laura F. Robinson, Tianyu Chen et al., “Rapid shifts in circulation and biogeochemistry of the Southern Ocean during deglacial carbon cycle events”, Science Advances 16 Oct 2020: Vol. 6, no. 42, eabb3807
DOI: 10.1126/sciadv.abb3807 (2) Chen, T., Robinson, L.F., Burke, A. et al. Persistently well-ventilated intermediate-depth ocean through the last deglaciation. Nat. Geosci. (2020). https://doi.org/10.1038/s41561-020-0638-6

Provided by University Of Bristol

In The Beginning, There Was Sugar (Chemistry / Planetary Science)

Organic molecules formed the basis for the evolution of life. But how could inorganic precursors have given rise to them? LMU chemist Oliver Trapp now reports a reaction pathway in which minerals catalyze the formation of sugars in the absence of water.

Prebiotic organic molecules could have been formed in such a setting at the dawn of life: Yellowstone Parc, USA. Photo: Oliver Trapp

More than 4 billion years ago, the Earth was very far from being the Blue Planet it would later become. At that point it had just begun to cool and, in the course of that process, the concentric structural zones that lie ever deeper beneath our feet were formed. The early Earth was dominated by volcanism, and the atmosphere was made up of carbon dioxide, nitrogen, methane, ammonia, hydrogen sulfide and water vapor. In this decidedly inhospitable environment the building blocks of life were formed. How then might this have come about?

Researchers have puzzled over the question for decades. The first breakthrough was made in 1953 by two chemists, named Stanley Miller and Harold C. Urey, at the University of Chicago. In their experiments, they simulated the atmosphere of the primordial Earth in a closed reaction system that contained the gases mentioned above. A miniature ‘ocean’ was heated to provide water vapor, and electrical discharges were passed through the system to mimic the effects of lightning. When they analyzed the chemicals produced under these conditions, Miller and Urey detected amino acids – the basic constituents of proteins – as well as a number of other organic acids.

It is now known that the conditions employed in these experiments did not reflect those that prevailed on the early Earth. Nevertheless, the Miller-Urey experiment initiated the field of prebiotic chemical evolution. However, it not throw much light on how other classes of molecules found in all biological cells – such as sugars, fats and nucleic acids – might have been generated. These compounds are however indispensable ingredients of the process that led to the first bacteria and subsequently to photosynthetic cyanobacteria that produced oxygen. This is why Oliver Trapp, Professor of Organic Chemistry at LMU, decided to focus his research on the prebiotic synthesis of these substances.

From formaldehyde to sugar

The story of synthetic routes from smaller precursors to sugars goes back almost a century prior to the Miller-Urey experiment. In 1861, the Russian chemist Alexander Butlerov showed that formaldehyde could give rise to various sugars via what became known as the formose reaction. Miller und Urey in fact found formic acid in their experiments, and it can be readily reduced to yield formaldehyde. Butlerov also discovered that the formose reaction is promoted by a number of metal oxides and hydroxides, including those of calcium, barium, thallium and lead. Notably calcium is abundantly available on and below the Earth’s surface.

However, the hypothesis that sugars could have been produced via the formose reaction runs into two difficulties. The ‘classical’ formose reaction produces a diverse mixture of compounds, and it takes place only in aqueous media. These requirements are at odds with the fact that sugars have been detected in meteorites.

Together with colleagues at LMU and the Max Planck Institute for Astronomy in Heidelberg, Trapp therefore decided to explore whether formaldehyde could give rise to sugars in a solid-phase system. With a view to simulating the kinds of mechanical forces to which solid minerals would have been subjected, all the reaction components were combined in a ball mill – in the absence of solvents, but adding enough formaldehyde to saturate the powdered solids

And indeed, the formose reaction was observed and several different minerals were found to catalyze it. The formaldehyde was adsorbed onto the solid particles, and the interaction resulted in the formation of the formaldehyde dimer (glycolaldehyde) – and ribose, the 5-carbon sugar that is an essential constituent of ribonucleic acid (RNA). RNA is thought to have merged prior to DNA, and it serves as the repository of genetic information in many viruses, as well as providing the templates for protein synthesis in all cellular organisms. More complex sugars were also obtained in the experiments, together with a few byproducts, such as lactic acid and methanol.

“Our results provide a plausible explanation for the formation of sugars in the solid phase, even under extraterrestrial settings in the absence of water,” says Trapp. They also prompt new questions that may point to new and unexpected prebiotic routes to the basic components of life as we know it, as Trapp affirms. “We are convinced that these new insights will open up entirely new perspectives for research on prebiotic, chemical evolution,” he says.

References: Haas, M., Lamour, S., Christ, S.B. et al. Mineral-mediated carbohydrate synthesis by mechanical forces in a primordial geochemical setting. Commun Chem 3, 140 (2020). https://doi.org/10.1038/s42004-020-00387-w

Provided by LMU Munich

Mesozoic Era Part 2: Cretaceous Period (Paleontology)

The name Cretaceous is derived from creta, Latin for chalk, and was first proposed by Omalius d’Halloy in 1822. D’Halloy had been commissioned to make a geologic map of France, and part of his task was to decide upon the geologic units to be represented by it. One of his units, the Terrain Crétacé, included chalks and underlying sands. The Cretaceous Period lasted about 80 million years from 145 million to 65 million years ago.

Cretaceous limestone

Chalk is a soft, fine-grained type of limestone composed predominantly of the armour-like plates of tiny floating algae that flourished during the Late Cretaceous. Most Cretaceous rocks are not chalks, but most chalks were deposited during the Cretaceous. Many of these rocks provide clear details of the period because they have not been deformed or eroded and are relatively close to the surface. An example is the White Cliffs of Dover between France and England. Continents were moving during the Cretaceous, busy remodeling life on earth. At the start of the period, dinosaurs ruled the remnants of the supercontinent Pangaea. Rodents scurried around the roots of forests of ferns and conifers.

Oceans filled huge gaps between isolated continents almost as they are today. See the map to the left above. In general, world oceans were about 300 to 600 feet higher in the Early Cretaceous and roughly 600 to 800 feet higher in the Late Cretaceous than they are today. Sea levels were higher during the Cretaceous than at any other time in earth’s history. The high Cretaceous sea levels were thought to be the result of water in the ocean basins being displaced by the growth of mid-ocean ridges.

Cretaceous period map

Approximately one-third of today’s landmass was underwater back then. For example, note on the map that the Rocky Mountains were not attached to the central part of the U.S., so, many mid-west states were under water. Also, most of Arabia as well as half of India (next to South Africa) were under water.

The Cretaceous picked up where the Jurassic left off: Gigantic sauropods (huge four legged monsters, see the picture below) led parades of dinosaurs through the forests, over plains, and along the coasts. Long-necked and toothy marine reptiles terrorized fish and mollusks in the seas. Hairy feathered birds filled the skies. In general, the climate of the Cretaceous Period was much warmer than at present, perhaps the warmest of any time in the earth’s history. The climate was also more equable in that the temperature differences between the poles and the Equator were about one-half that of the present difference.

Sauropod

Though dinosaurs ruled throughout the Cretaceous, the dominant groups shifted and many new types evolved. Sauropods dominated the southern continents but were rare in the north. Herd dwelling Iguanodon (four legged beasts with short stubby tails given below) spread everywhere but Antarctica. Toward the close of the Cretaceous, vast herds of horned beasts such as Triceratops (medium four legged beasts with two horns on heir heads) munched low-lying plants on the northern continents. The carnivore Tyrannosaurus rex dominated the late Cretaceous in the north while monstrous meat-eaters like Spinosaurus (big two legged dinosaurs, similar to T-rex only larger) that had a huge sail-like fin on their backs, thrived in the south. Dinosaurs roamed Antarctica, even with its long winter nights.

Iguanodon

Other creatures, such as frogs, salamanders, turtles, crocodiles, and snakes, proliferated on the expanded coasts. Shrew-like mammals scurried about the forests. The huge pterosaur flying reptile soared overhead, though the group as a whole faced ever stiffening competition from fast diversifying birds. Ancestors to modern pelicans and sandpipers all showed up in the Cretaceous. However, it was the rapid dispersal of flowering plants that stole the show in the Cretaceous. They spread with the help of insects from bees and wasps to ants and beetles. Magnolia, ficus, and sassafras quickly outnumbered ferns, conifers, gingkoes, and cycads.

To be continued..