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Atlantic hurricane season 2023: El Niño and extreme Atlantic Ocean heat are about to clash

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Atlantic hurricane season 2023: El Niño and extreme Atlantic Ocean heat are about to clash

Hurricane Florence, seen from the International Station in 2018. Atlantic hurricane season runs from June 1 to Nov. 30.
NASA

Christina Patricola, Iowa State University

The Atlantic hurricane season starts on June 1, and forecasters are keeping a close eye on rising ocean temperatures, and not just in the Atlantic.

Globally, warm sea surface temperatures that can fuel hurricanes have been off the charts in the spring of 2023, but what really matters for Atlantic hurricanes are the ocean temperatures in two locations: the North Atlantic basin, where hurricanes are born and intensify, and the eastern-central tropical Pacific Ocean, where El Niño forms.

This year, the two are in conflict – and likely to exert counteracting influences on the crucial conditions that can make or break an Atlantic hurricane season. The result could be good for the Caribbean and Atlantic coasts: a near-average hurricane season. But forecasters are warning that that hurricane hinges on El Niño panning out.

Ingredients of a hurricane

In general, hurricanes are more likely to form and intensify when a tropical low-pressure system encounters an environment with warm upper-ocean temperatures, moisture in the atmosphere, instability and weak vertical wind shear.

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Warm ocean temperatures energy for a hurricane to develop. Vertical wind shear, or the difference in the strength and direction of winds between the lower and upper regions of a tropical storm, disrupts the organization of convection – the thunderstorms – and brings dry into the storm, inhibiting its growth.

How hurricanes form. National Geographic.

The Atlantic Ocean's role

The Atlantic Ocean's role is pretty straightforward. Hurricanes draw energy from warm ocean water beneath them. The warmer the ocean temperatures, the better for hurricanes, all else being equal.

Tropical Atlantic Ocean temperatures were unusually warm during the most active Atlantic hurricane seasons on recent record. The 2020 Atlantic hurricane season produced a record 30 named tropical cyclones, while the 2005 Atlantic hurricane season produced 28 named storms, a record 15 of which became hurricanes, .

Two maps showing tropical cyclone tracks. The tracks correspond with warmer water temperatures in the sea surface temperature maps below.
The top images show where Atlantic tropical storms traveled in 2005, on the left, and in 2020, on the right. The lower images show the corresponding sea surface temperature anomalies for the August-October peak of the hurricane season compared with the August-October 1991-2020 average in degrees Celsius.
NOAA

How the Pacific Ocean gets involved

The tropical Pacific Ocean's role in Atlantic hurricane formation is more complicated.

You may be wondering, how can ocean temperatures on of the Americas influence Atlantic hurricanes? The answer lies in teleconnections. A teleconnection is a chain of processes in which a change in the ocean or atmosphere in one region to large-scale changes in atmospheric circulation and temperature that can influence the weather elsewhere.

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Sea surface temperature anomalies in degrees Celsius observed during three El Niño events show differences in location and strength of ocean warming.
Three examples of of how sea surface temperatures in the tropical Pacific change during El Niño .
Christina Patricola

One recurring pattern of tropical Pacific climate variability that initiates teleconnections is the El Niño-Southern Oscillation.

When the tropical eastern-central Pacific Ocean is unusually warm, El Niño can form. During El Niño events, the warm upper-ocean temperatures change the vertical and east-west atmospheric circulation in the tropics. That initiates a teleconnection by affecting the east-west winds in the upper atmosphere throughout the tropics, ultimately resulting in stronger vertical wind shear in the Atlantic basin. That wind shear can tamp down hurricanes.

Two illustrations of Walker Circulation patterns. El Niño reverses direction and strength compared with a neutral ENSO, or El Niño-Southern Oscillation.
How El Niño conditions affect the Walker Circulation's air flow, which can affect weather around the world.
Fiona Martin/NOAA Climate.gov

That's what forecasters are expecting to happen this summer. The latest forecasts show a 90% likelihood that El Niño will develop by August and stay strong through the fall peak of the hurricane season.

A tug of war between Atlantic and Pacific influences

My research and work by other atmospheric scientists has shown that a warm Atlantic and a warm tropical Pacific tend to counteract each other, leading to near-average Atlantic hurricane seasons.

Both observations and climate model simulations have shown that outcome. The National Oceanic and Atmospheric Administration's 2023 forecast calls for a near-average 12 to 17 named storms, five to nine hurricanes and one to four major hurricanes. An earlier outlook from Colorado State University forecasters anticipates a slightly below-average season, with 13 named storms, compared with a climatological average of 14.4.

Map showing warmer than normal temperatures across the Gulf of Mexico and Atlantic Ocean south of the Virginia.
Sea surface temperature anomaly in degrees Celsius forecast for August to October 2023 shows a warm season relative to the 1991-2020 average for the same months.
Based on NCEP Climate Forecast System version 2 (CFSv2)

The wild cards to watch

Although tropical Atlantic and Pacific Ocean temperatures often inform skillful seasonal hurricane forecasts, there are other factors to consider and monitor.

First, will the forecast El Niño and Atlantic warming pan out? If one or the other does not, that could tip the balance in the tug of war between the influences.

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The Atlantic Coast should be rooting for El Niño to develop as forecast, since such events often reduce hurricane impacts there. If this year's expected Atlantic Ocean warming were instead paired with La Niña – El Nino's opposite, characterized by cool tropical Pacific waters – that could have led to a record-breaking active season instead.

Two other factors are also important. The Madden-Julian Oscillation, a pattern of clouds and rainfall that travels eastward through the tropics on a time scale of 30 to 90 days, can either encourage or suppress tropical storm formation. And dust storms from the Saharan air layer, which contains warm, dry and dusty air from Africa, can suppress tropical cyclones.The Conversation

Christina Patricola, Assistant Professor of Atmospheric Sciences, Iowa State University

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

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Do hormonal contraceptives increase depression risk? A neuroscientist explains how they affect your mood, for better or worse

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theconversation.com – Natalie C. Tronson, Associate Professor of Psychology, of Michigan – 2024-06-24 07:20:05

Hormonal contraceptives have functions that go beyond just birth control.

Mindful Media/E+ via Getty Images

Natalie C. Tronson, University of Michigan

More than 85% of women – and more than 300 million people worldwide at any given time – use hormonal contraceptives for at least five years of their . Although primarily taken for birth control, many people also use hormonal contraceptives to manage a variety of symptoms related to menstruation, from cramps and acne to mood swings.

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For up to 10% of women, however, hormone contraceptives can increase their risk of depression. Hormones, estrogen and progesterone, are crucial for brain . So, how does modifying hormone levels with hormone contraceptives affect mental health?

I am a researcher studying the neuroscience of stress and emotion-related processes. I also study sex differences in vulnerability and resilience to mental health disorders. Understanding how hormone contraceptives affect mood can help researchers predict who will experience positive or negative effects.

How do hormone contraceptives work?

In the U.S. and other western countries, the most common form of hormonal contraceptive is “the pill” – a combination of a synthetic estrogen and a synthetic progesterone, two hormones involved in regulation of the menstrual cycle, ovulation and pregnancy. Estrogen coordinates the timed release of other hormones, and progesterone maintains a pregnancy.

This may seem counterintuitive – why do naturally occurring hormones required for pregnancy also prevent pregnancy? And why does taking a hormone reduce the levels of that same hormone?

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Line graph plotting rising estrogen levels peaking at day one of the menstrual cycle before decreasing, and progestorone levels peaking at day eight before dereasing

When estrogen and progesterone reach a certain threshold level, the body decreases their production.

Dharani Kalidasan/R.I. McLachlan et al. 1987 via Wikimedia Commons, CC BY-SA

Hormone cycles are tightly controlled by the hormones themselves. When progesterone levels increase, it activates processes in cells that shut off production of more progesterone. This is called a negative feedback loop.

Estrogen and progesterone from the pill, or other common forms of contraceptives such as implants or vaginal rings, cause the body to decrease production of those hormones, reducing them to levels observed outside the fertile window of the cycle. This disrupts the tightly orchestrated hormonal cycle required for ovulation, menstruation and pregnancy.

Brain effects of hormonal contraceptives

Hormonal contraceptives affect more than just the ovaries and uterus.

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The brain, specifically an area called the hypothalamus, controls the synchronization of ovarian hormone levels. Although they're called “ovarian hormones,” estrogen and progesterone receptors are also present throughout the brain.

Estrogen and progesterone have broad effects on neurons and cellular processes that have nothing to do with reproduction. For example, estrogen plays a role in processes that control memory formation and protect the brain against . Progesterone helps regulate emotion.

By changing the levels of these hormones in the brain and the body, hormonal contraceptives may modulate mood – for better or for worse.

Hormonal contraceptives interact with stress

Estrogen and progesterone also regulate the stress response – the body's “fight-or-flight” reaction to physical or psychological challenges.

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The main hormone involved in the stress response – cortisol in humans and corticosterone in rodents, both abbreviated to CORT – is primarily a metabolic hormone, meaning that increasing blood levels of these hormones during stressful conditions results in more energy mobilized from fat stores. The interplay between stress and reproductive hormones is a crucial link between mood and hormone contraceptives, as energy regulation is extremely important during pregnancy.

So what happens to someone's stress response when they're on hormonal contraceptives?

When exposed to a mild stressor – sticking an arm in cold , for example, or standing to give a public speech – women using hormone contraceptives show a smaller increase in CORT than people not on hormone contraceptives.

Stressed person looking at laptop with elbows leaning on surface and clasped hands over mouth

Chronic stress can worsen mood.

Vera Livchak/Moment via Getty Images

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Researchers saw the same effect in rats and mice – when treated daily with a combination of hormones that mimic the pill, female rats and mice also show a suppression of the stress response.

Hormonal contraceptives and depression

Do hormonal contraceptives increase depression risk? The short answer is it varies from person to person. But for most people, probably not.

It's important to note that neither increased nor decreased stress responses are directly related to risk for or resilience against depression. But stress is closely related to mood, and chronic stress substantially increases risk for depression. By modifying stress responses, hormone contraceptives change the risk for depression after stress, leading to “protection” against depression for many people and “increased risk” for a minority of people. More than 9 out of 10 people who use hormonal contraceptives will not experience decreased mood or depression symptoms, and many will experience improved mood.

But researchers don't yet know who will experience increased risk. Genetic factors and previous stress exposures increase risk for depression, and it seems that similar factors contribute to mood changes related to hormone contraception.

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Currently, hormone contraceptives are usually prescribed by trial and error – if one type causes side effects in a patient, another with a different dose, delivery method or formulation might be better. But the of “try-and-see” is inefficient and frustrating, and many people give up instead of switching to a different option. Identifying the specific factors that increase depression risk and better communicating the benefits of hormone contraception beyond birth control can help patients make more informed decisions.The Conversation

Natalie C. Tronson, Associate Professor of Psychology, University of Michigan

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

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Why do some planets have moons? A physics expert explains why Earth has only one moon while other planets have hundreds

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theconversation.com – Nicole Granucci, Instructor of Physics, Quinnipiac – 2024-06-24 07:18:47

Some planets, such as Saturn, have more than a hundred moons, while others, such as Venus, have none.

NASA/JPL-Caltech/Space Science Institute via AP

Nicole Granucci, Quinnipiac University

Curious Kids is a for of all ages. If you have a question you'd like an expert to answer, send it to curiouskidsus@theconversation.com.

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Why do some planets have moons and some don't? – Siddharth, age 6,


On Earth, you can look up at night and see the Moon shining bright from hundreds of thousands of miles away. But if you went to Venus, that wouldn't be the case. Not every planet has a moon – so why do some planets have several moons, while others have none?

I'm a physics instructor who has followed the current theories that describe why some planets have moons and some don't.

First, a moon is called a natural satellite. Astronomers refer to satellites as objects in space that orbit larger bodies. Since a moon isn't human-made, it's a natural satellite.

Currently, there are two main theories for why some planets have moons. Moons are either gravitationally captured if they are within what's called a planet's Hill sphere radius, or they're formed along with a solar system.

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The Hill sphere radius

Objects exert a gravitational force of attraction on other nearby objects. The larger the object is, the greater the force of attraction.

This gravitational force is the reason we all stay grounded to Earth instead of floating away.

The solar system is dominated by the Sun's large gravitational force, which keeps all of the planets in orbit. The Sun is the most massive object in our solar system, which means it has the most gravitational influence on objects such as planets.

In order for a satellite to orbit a planet, it has to be close enough for the planet to exert enough force to keep it in orbit. The minimum distance for a planet to keep a satellite in orbit is called the Hill sphere radius.

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The Hill sphere radius is based on the mass of both the larger object and the smaller object. The Moon orbiting Earth is a good example of how the Hill sphere radius works. The Earth orbits around the Sun, but the Moon is close enough to Earth that Earth's gravitational pull captures it. The moon orbits around the Earth, rather than the Sun, because it is within Earth's Hill sphere radius.

A diagram showing Earth, with a long radius around it and a circle representing the Moon within that radius, and Mercury, with a short radius around it.

Earth has a larger Hill sphere radius than Mercury.

Nicole Granucci

Small planets like Mercury and Venus have a tiny Hill sphere radius, since they can't exert a large gravitational pull. Any potential moons would likely get pulled in by the Sun instead.

Many scientists are still looking to see whether these planets may have had small moons in the past. Back during the formation of the solar system, they may have had moons that got knocked away by collisions with other objects.

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Mars has two moons, Phobos and Deimos. Scientists still debate whether these came from asteroids that passed close into Mars' Hill sphere radius and got captured by the planet, or if they were formed at the same time as the solar system. More evidence supports the first theory, because Mars is close to the asteroid belt.

Jupiter, Saturn, Uranus and Neptune have larger Hill sphere radii, because they are much larger than Earth, Mars, Mercury and Venus and they're farther from the Sun. Their gravitational pulls can attract and keep more natural satellites such as moons in orbit. For example, Jupiter has 95 moons, while Saturn has 146.

Moons forming with a solar system

Another theory suggests that some moons formed at the same time as their solar system.

Solar start out with a big disk of gas rotating around a sun. As the gas rotates around the sun, it condenses into planets and moons that rotate around them. The planets and moons then all rotate in the same direction.

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This animation shows how the planets in our solar system formed. The dark rings in the disk represent the formation of the planets and moons. Eventually, the gas condenses into planets, natural satellites and asteroids.

But only a few moons in our solar system were likely created this way. Scientists predict that Jupiter's and Saturn's inner moons formed during the emergence of our solar system because they're so old. The rest of the moons in our solar system, Jupiter's and Saturn's outer moons, were probably gravitationally captured by their planets.

Earth's Moon is special because it likely formed in a different way. Scientists believe that long ago, a large, Mars-sized object collided with the Earth. During that collision, a big chunk flew off the Earth and into its orbit and became the Moon.

This animation from NASA shows a simulation of how our Moon was formed during the collision.

Scientists guess that the Moon formed this way because they've found a type of rock called basalt in soil on the Moon's surface. The Moon's basalt looks the same as basalt found inside the Earth.

Ultimately, the question of why some planets have moons is still widely debated, but factors such as a planet's size, gravitational pull, Hill sphere radius and how its solar system formed may play a role.

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Hello, curious kids! Do you have a question you'd like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the where you .

And since curiosity has no age limit – adults, let us know what you're wondering, too. We won't be able to answer every question, but we will do our best.The Conversation

Nicole Granucci, Instructor of Physics, Quinnipiac University

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

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Rocks on Rapa Nui tell the story of a small, resilient population − countering the notion of a doomed overpopulated island

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theconversation.com – Carl Lipo, Professor of Anthropology and Associate Dean for Research, Binghamton , State University of New York – 2024-06-21 13:05:50
Covering the ground with rocks is actually a good way to grow some crops in poor soil.
Carl Lipo

Carl Lipo, Binghamton University, State University of New York

Conventional wisdom that the island of Rapa Nui, also known as Easter Island, once had a large population that crashed after living beyond its means and stripping the island of resources. A new research study my colleagues and I conducted has struck another blow to this notion by using artificial intelligence to analyze satellite data about piles of rocks on this tiny island in the middle of the Pacific Ocean.

Our study looked at rock gardens, a form of subsistence farming, and determined that the island – just 15.3 miles (24.6 km) long by 7.6 miles (12.3 km) at its widest point – likely never held many more than the 3,000 or so people European explorers encountered in 1722.

The conventional wisdom grew out of speculation about another set of stone structures on the island: the iconic massive statues, called moai, that ancestors of Rapanui people carved. The statues tower as high as a three-story building and weigh up to 70 tons. There are nearly 1,000 of them across the island.

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For an archaeologist, the mystery of what led people to invest so much time and energy in building these colossal figures begs for an explanation. For the past 24 years, my colleagues and I have been searching for one.

Some of the earliest European visitors assumed that the island must have hosted a much larger population at one point to account for the number and magnitude of the moai. This assumption has been repeated for generations and forms the basis of a collapse narrative.

The collapse story holds that the island must have once had tens of thousands of inhabitants needed for the labor involved in carving and transporting the massive statues. Such a large population was not sustainable, and ultimately shortfalls in food resulted in starvation, warfare and even cannibalism. Consequently, the population plummeted to the meager numbers observed by the early European explorers.

large stone carved heads sit on a grassy treeless aside
Did it really take an excessively large population to carve and transport these giant stone statues centuries ago?
AP Photo/Karen Schwartz

In our previous studies of the island my colleagues and I asked ourselves, if there were so many people living on the island at some point before European arrival, where is the evidence? We undertook a new study to examine whether such a large population was possible, given how Rapanui people used rock gardens to grow much of their food. From our evaluation of the available data, our best estimate is that there were never more than 3,000 to 4,000 people, and they lived sustainably on the island.

What rocks say about farming

In this study, we examined the archaeological record of how the Rapanui used rock gardening to grow their main crop, the sweet potato. Rock gardening is a form of cultivation in which broken pieces of bedrock are added to the soil to enrich it. Extensive rock garden cultivation plots are found across the island and would have provided a critical food source augmented by marine resources.

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Previous studies have noted the extent of these gardens and concluded that these efforts might have supported up to 16,000 people. Our fieldwork, however, found that many of the that this study identified as rock gardens were misidentified. So we needed to conduct a more detailed analysis to get a better estimate of rock gardening, which would give us a more reliable source of information about maximum possible population sizes.

We combined fieldwork with new analyses of satellite imagery. During our fieldwork, we looked on the ground for clear examples of rock gardening. We knew we were at locations of rock gardening when we found patches covered with rocks in places that could not be easily explained as the result of erosion. Obsidian artifacts among the rocks confirmed that the areas were used for cutting and processing sweet potatoes. Often, these areas have another root crop, taro, growing in them even . We also identified places that might resemble rock mulch gardens but were just bedrock outcrops or random scatters of cobbles and boulders.

We then acquired WorldView-3 satellite imagery for the entire island. The WorldView-3 satellite collects high-resolution visible light photos of the Earth's surface and images that record shortwave infrared information. Shortwave infrared includes wavelengths that range between 900 nm and 2,500 nm, longer than are visible to the human eye. Shortwave infrared is helpful for distinguishing materials that look identical to the unaided eye. In particular, shortwave infrared is sensitive to differences in moisture, an essential attribute of productive agricultural fields.

Using our field data, we trained machine learning models to distinguish rock mulch gardening areas from those that are not. Machine learning generates an algorithm that can detect subtle differences – and can do so repeatedly and systematically. In this way, we could examine nearly the entire island quickly and without spending years doing field mapping.

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A map of a triangular shaped island
Red dots indicate rock gardens detected by satellite imagery.
Dylan Davis, CC BY

Our analyses dramatically reduced the island's total area that can be associated with rock gardening, from a range of 1.6 to 8.1 square miles (4.3 to 21.1 square kilometers) down to 0.29 square miles (0.76 square kilometers). When we entered estimates for the productivity of these areas, our calculations showed that the maximum number of people this form of cultivation can is about 3,000, quite similar to the conclusions we reached with other sources of information.

Resilience rather than hubris

Over the past 20 years, researchers have generated significant new evidence about the archaeological record of Rapa Nui, contributing to reframing the island's narrative away from the idea of collapse. For example, studies from my team demonstrate that the statues were moved in a walking fashion from the quarry to their final locations on platforms called ahu. We have also tackled the question of how the islanders placed giant multiton hats called pukao on the tops of these statues.

However, the idea that there were much larger numbers of people on the island remains embedded in the academic and popular literature. The persistence of this idea has consequences outside of the field of Rapa Nui archaeology. Despite archaeological evidence to the contrary, it is not uncommon, for example, for ecologists to use Rapa Nui as a case study of so-called Malthusian demographics, where the population is assumed to have reached a massive peak that momentarily outstripped the island's resources and triggered an ecological catastrophe.

While my colleagues and I agree that it is essential to be concerned about the potential for exploitation of natural resources, catastrophe is not the only possibility. Human history offers many examples demonstrating how it is possible to sustainably despite constraints.

On Rapa Nui, we have learned that its people did not experience a population collapse before the arrival of Europeans but instead succeeded due to their ingenuity. Rapanui people found clever ways of adapting to the island and practiced sustainable farming to support themselves. This research adds details about the capacity of rock gardens to grow food and support the population of the island.

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A pile of rocks on a sunny treeless hillside
Rock gardens add nutrients and retain moisture in poor soil.
Carl Lipo

Our increasing understanding of the island has critical implications for the future. In learning how to thrive in a limited , society can adopt strategies used by people in the past. The archaeological record of Rapa Nui points to the idea that efforts that bring communities together in cooperative and competitive ways, such as moai carving and transport, to greater resiliency in times of shortfall.

In the end, the history of Rapa Nui is not a cautionary tale but a source of inspiration that may be key to humanity's future.The Conversation

Carl Lipo, Professor of Anthropology and Associate Dean for Research, Binghamton University, State University of New York

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

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