Annalisa Bracco, Georgia Institute of Technology and Zachary Handlos, Georgia Institute of Technology

The North Atlantic Ocean has been running a fever for months, with surface temperatures at or near record highs. But cooling along the equator in both the Atlantic and eastern Pacific may finally be starting to bring some relief, particularly for vulnerable coral reef ecosystems.

This cooling is related to two climate phenomena with similar names: La Niña, which forms in the tropical Pacific, and the less well-known Atlantic Niña.

Both can affect the Atlantic hurricane season. While La Niña tends to bring conditions ideal for Atlantic hurricanes, the less powerful Atlantic Niña has the potential to reduce some of the hurricane risk.

We’re ocean and atmospheric scientists who study this type of climate phenomenon. It’s rare to see both Niñas at the same time, yet in August 2024, both appeared to be developing. Let’s take a closer look at what that means.

La Niña and its cousin, Atlantic Niña

La Niña is part of the El Niño–Southern Oscillation, a well-known climate phenomenon that has widespread effects on climate and weather around the world.

During La Niña, sea surface temperatures in the tropical Pacific dip below normal. Easterly trade winds then strengthen, allowing more cool water to well up along the equator off South America. That cooling affects the atmosphere in ways that reverberate across the planet. Some areas become stormier and others drier during La Niña, and the wind shear that can tear apart Atlantic hurricanes tends to weaken.

La Niña and its warmer opposite, El Niño, oscillate every three to four years or so. https://www.youtube.com/embed/wVlfyhs64IY?wmode=transparent&start=0 La Niña and its opposite, El Niño, explained. NOAA.

A similar climate phenomenon, Atlantic Niña, occurs in the Atlantic Ocean but at a much smaller scale and amplitude. It typically peaks around July or August and tends to have a shorter duration than its Pacific cousin, and much more modest and local impacts. Atlantic Niñas generally have the opposite effect of Atlantic Niños, which tend to reduce rainfall over Africa’s Sahel region and increase rainfall in Brazil and the countries that surround the Gulf of Guinea, such as Ghana, Nigeria and Cameroon.

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While much weaker than their Pacific counterpart, Atlantic Niñas can, however, partially counteract La Niñas by weakening summer winds that help drive the upwelling that cools the eastern Pacific.

Why might both happen now?

In July and August 2024, meteorologists noted cooling that suggested an Atlantic Niña might be developing along the equator. The winds at the ocean surface had been weak through most of the summer, and sea surface temperatures there were quite warm until early June, so signs an Atlantic Niña might be emerging were a surprise.

At the same time, waters along the equator in the eastern Pacific were also cooling, with La Niña conditions expected there around October or November.

Getting a Pacific-Atlantic Niña combination is rare but not impossible. It’s like finding two different pendulums that are weakly coupled to swing in opposite directions moving together in time. The combinations of La Niña and Atlantic Niño, or El Niño and Atlantic Niña are more common.

Good news or bad for hurricane season?

An Atlantic Niña may initially suggest good news for those living in hurricane-prone areas.

Cooler than average waters off the coast of Africa can suppress the formation of African easterly waves. These are clusters of thunderstorm activity that can form into tropical disturbances and eventually tropical storms or hurricanes.

Tropical storms draw energy from the process of evaporating water associated with warm sea surface temperatures. So, cooling in the tropical Atlantic could weaken this process. That would leave less energy for thunderstorms, which would reduce the probability of a tropical cyclone forming.

However, NOAA takes all factors into account when it updates its Atlantic hurricane season outlook, released in early August, and it still anticipates an extremely active 2024 season. Tropical storm season typically peaks in early to mid-September.

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Two reasons are behind the busy forecast: The near record-breaking warm sea surface temperatures in much of the North Atlantic can strengthen hurricanes. And the expected development of a La Niña in the Pacific tends to weaken wind shear – the change in wind speed with height that can tear apart hurricanes. La Niña’s much stronger effects can override any impacts associated with the Atlantic Niña.

Exacerbating the problem: Global warming

The past two years have seen exceptionally high ocean temperatures in the Atlantic and around much of the world’s oceans. The two Niñas are likely to contribute some cooling relief for certain regions, but it may not last long.

In addition to these cycles, the global warming trend caused by rising greenhouse gas emissions is raising the baseline temperatures and can fuel major hurricanes.

Annalisa Bracco, Professor of Ocean and Climate Dynamics, Georgia Institute of Technology and Zachary Handlos, Atmospheric Science Educator, Georgia Institute of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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The Polaris Dawn mission has etched its name in the annals of space history, marking a significant milestone in human spaceflight. After a groundbreaking five-day journey, the SpaceX Crew Dragon capsule, carrying a crew of four astronauts, splashed down safely in the Gulf of Mexico at 3:37 a.m. ET on Sunday. This mission not only showcased the capabilities of commercial space travel but also achieved several remarkable feats, including the world’s first commercial spacewalk.

A Historic Splashdown

The Crew Dragon capsule landed off the coast of Dry Tortugas, Florida, concluding a mission that saw its crew reach unprecedented heights. Polaris Dawn achieved an orbital altitude of 870 miles (1,400 kilometers), the highest ever reached by humans since the Apollo program, surpassing the previous record set by NASA’s Gemini 11 mission in 1966, which reached 853 miles (1,373 kilometers).

Upon re-entry, the spacecraft faced extreme temperatures of up to 3,500 degrees Fahrenheit (1,900 degrees Celsius) due to the pressures and friction of traveling at 17,000 miles per hour (27,000 kilometers per hour). However, the Crew Dragon’s advanced heat shield ensured the astronauts remained safe and comfortable throughout the descent. Once the capsule hit the water, it bobbed momentarily before rescue crews aboard a vessel dubbed the “Dragon’s Nest” retrieved it, completing a meticulous safety check before the crew disembarked.

Groundbreaking Achievements

The Polaris Dawn crew consisted of mission commander Jared Isaacman, a billionaire entrepreneur and CEO of Shift4 Payments; former US Air Force pilot Scott “Kidd” Poteet; and SpaceX operations engineers Anna Menon and Sarah Gillis. This mission was the first of three planned in the Polaris program, intended to push the boundaries of human spaceflight.

One of the most significant highlights of the mission was the first-ever commercial spacewalk. Conducted on the third day, both Isaacman and Gillis exited the spacecraft in a groundbreaking extravehicular activity (EVA). With the absence of an airlock in the Crew Dragon, the entire cabin was depressurized, exposing all four crew members to the vacuum of space. Gillis, at just 30 years old, became the youngest person to participate in a spacewalk, while the mission set a new record for the number of individuals simultaneously exposed to space, totaling four.

Scientific Exploration

The Polaris Dawn mission also focused on scientific research, particularly studying the effects of space radiation on the human body. By flying through parts of the Van Allen radiation belt, the crew aimed to gather valuable data that could inform future long-duration space missions, including potential journeys to Mars.

The mission kicked off with a rigorous pre-breathing protocol to reduce nitrogen levels in the crew’s bodies, mitigating the risk of decompression sickness during the planned spacewalk. Over the course of the mission, the cabin pressure was gradually decreased from 14.5 to 8.6 pounds per square inch, while oxygen levels were increased to prepare for the EVA.

Breaking Barriers for Women in Space

Notably, Menon and Gillis broke records by flying further from Earth than any women before them. Their participation in this historic mission highlights the increasing role of women in space exploration, paving the way for future generations of female astronauts.

The Polaris Dawn mission represents a pivotal moment in commercial spaceflight, illustrating the potential of private companies to lead the way in exploring new frontiers. As SpaceX continues to innovate and push the boundaries of what is possible, the accomplishments of the Polaris Dawn crew serve as a reminder of humanity’s enduring quest to explore the cosmos.

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Conclusion

The Polaris Dawn mission has set the stage for a new era in space exploration, showcasing the capabilities of commercial ventures and the resilience of the human spirit. As we look forward to the upcoming missions in the Polaris program, the accomplishments of this crew will undoubtedly inspire future explorers to reach for the stars.

https://www.cnn.com/2024/09/15/science/spacex-polaris-dawn-splashdown-landing/index.html

Sources: Polaris Dawn, SpaceX, Wikipedia, CNN

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Chantal Nguyen, University of Colorado Boulder

Most of us aren’t spending our days watching our houseplants grow. We see their signs of life only occasionally – a new leaf unfurled, a stem leaning toward the window.

But in the summer of 1863, Charles Darwin lay ill in bed, with nothing to do but watch his plants so closely that he could detect their small movements to and fro. The tendrils from his cucumber plants swept in circles until they encountered a stick, which they proceeded to twine around.

“I am getting very much amused by my tendrils,” he wrote.

This amusement blossomed into a decadeslong fascination with the little-noticed world of plant movements. He compiled his detailed observations and experiments in a 1880 book called “The Power of Movement in Plants.”

In one study, he traced the motion of a carnation leaf every few hours over the course of three days, revealing an irregular looping, jagged path. The swoops of cucumber tendrils and the zags of carnation leaves are examples of inherent, ubiquitous plant movements called circumnutations – from the Latin circum, meaning circle, and nutare, meaning to nod.

Circumnutations vary in size, regularity and timescale across plant species. But their exact function remains unclear.

I’m a physicist interested in understanding collective behavior in living systems. Like Darwin, I’m captivated by circumnutations, since they may underlie more complex phenomena in groups of plants.

Sunflower patterns

A 2017 study revealed a fascinating observation that got my colleagues and me wondering about the role circumnutations could play in plant growth patterns. In this study, researchers found that sunflowers grown in a dense row naturally formed a near-perfect zigzag pattern, with each plant leaning away from the row in alternating directions.

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This pattern allowed the plants to avoid shade from their neighbors and maximize their exposure to sunlight. These sunflowers flourished.

Researchers then planted some plants at the same density but constrained them so that they could grow only upright without leaning. These constrained plants produced less oil than the plants that could lean and get the maximum amount of sun.

While farmers can’t grow their sunflowers quite this close together due to the potential for disease spread, in the future they may be able to use these patterns to come up with new planting strategies.

Self-organization and randomness

This spontaneous pattern formation is a neat example of self-organization in nature. Self-organization refers to when initially disordered systems, such as a jungle of plants or a swarm of bees, achieve order without anything controlling them. Order emerges from the interactions between individual members of the system and their interactions with the environment.

Somewhat counterintuitively, noise – also called randomness – facilitates self-organization. Consider a colony of ants.

Ants secrete pheromones behind them as they crawl toward a food source. Other ants find this food source by following the pheromone trails, and they further reinforce the trail they took by secreting their own pheromones in turn. Over time, the ants converge on the best path to the food, and a single trail prevails.

But if a shorter path were to become possible, the ants would not necessarily find this path just by following the existing trail.

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If a few ants were to randomly deviate from the trail, though, they might stumble onto the shorter path and create a new trail. So this randomness injects a spontaneous change into the ants’ system that allows them to explore alternative scenarios.

Eventually, more ants would follow the new trail, and soon the shorter path would prevail. This randomness helps the ants adapt to changes in the environment, as a few ants spontaneously seek out more direct ways to their food source.

In biology, self-organized systems can be found at a range of scales, from the patterns of proteins inside cells to the socially complex colonies of honeybees that collectively build nests and forage for nectar.

Randomness in sunflower self-organization

So, could random, irregular circumnutations underpin the sunflowers’ self-organization?

My colleagues and I set out to explore this question by following the growth of young sunflowers we planted in the lab. Using cameras that imaged the plants every five minutes, we tracked the movement of the plants to see their circumnutatory paths.

We saw some loops and spirals, and lots of jagged movements. These ultimately appeared largely random, much like Darwin’s carnation. But when we placed the plants together in rows, they began to move away from one another, forming the same zigzag configurations that we’d seen in the previous study.

We analyzed the plants’ circumnutations and found that at any given time, the direction of the plant’s motion appeared completely independent of how it was moving about half an hour earlier. If you measured a plant’s motion once every 30 minutes, it would appear to be moving in a completely random way.

We also measured how much the plant’s leaves grew over the course of two weeks. By putting all of these results together, we sketched a picture of how a plant moved and grew on its own. This information allowed us to computationally model a sunflower and simulate how it behaves over the course of its growth.

A sunflower model

We modeled each plant simply as a circular crown on a stem, with the crown expanding according to the growth rate we measured experimentally. The simulated plant moved in a completely random way, taking a “step” every half hour.

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We created the model sunflowers with circumnutations of lower or higher intensity by tweaking the step sizes. At one end of the spectrum, sunflowers were much more likely to take tiny steps than big ones, leading to slow, minimal movement on average. At the other end were sunflowers that are equally as likely to take large steps as small steps, resulting in highly irregular movement. The real sunflowers we observed in our experiment were somewhere in the middle.

Plants require light to grow and have evolved the ability to detect shade and alter the direction of their growth in response.

We wanted our model sunflowers to do the same thing. So, we made it so that two plants that get too close to each other’s shade begin to lean away in opposite directions.

Finally, we wanted to see whether we could replicate the zigzag pattern we’d observed with the real sunflowers in our model.

First, we set the model sunflowers to make small circumnutations. Their shade avoidance responses pushed them away from each other, but that wasn’t enough to produce the zigzag – the model plants stayed stuck in a line. In physics, we would call this a “frustrated” system.

Then, we set the plants to make large circumnutations. The plants started moving in random patterns that often brought the plants closer together rather than farther apart. Again, no zigzag pattern like we’d seen in the field.

But when we set the model plants to make moderately large movements, similar to our experimental measurements, the plants could self-organize into a zigzag pattern that gave each sunflower optimal exposure to light.

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So, we showed that these random, irregular movements helped the plants explore their surroundings to find desirable arrangements that benefited their growth.

Plants are much more dynamic than people give them credit for. By taking the time to follow them, scientists and farmers can unlock their secrets and use plants’ movement to their advantage.

Chantal Nguyen, Postdoctoral Associate at the BioFrontiers Institute, University of Colorado Boulder

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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