Ocean scientists confront the invisible inferno
By Camille Richir |
February 16, 2024
Month after month, year after year, water surface temperatures are setting new records. As of February 12, 2024, the global average reached 21.1°C, nearly one degree higher than the average from 1980 to 2011. This warming trend extends deep below the surface: the amount of energy absorbed by the oceans has also shattered all previous records, according to two studies published back-to-back in January by the American National Oceanic and Atmospheric Administration and the Chinese Institute of Atmospheric Physics.
To put it in perspective, in 2023, the heat content in the oceans from the surface down to 2,000 meters increased by between 9 and 15 zettajoules—a stark contrast to the annual human energy consumption of 0.5 zettajoule.
Despite these staggering figures, they barely capture the magnitude of the upheaval in this vast body of water that covers 70% of the Earth's surface. How do we narrate a world turned upside down when it remains out of reach for most humans? How do we describe an ocean that "burns" when most of its impacts seem invisible?
In an effort to grasp what's at stake, without claiming to cover every aspect, La Croix spoke to three oceanographers. Through their dives, measurements at sea or from the sky, they stand as sentinels of ocean warming, sharing their concerns about the changes unfolding before their eyes. Yet, they avoid fatalism, emphasizing the collective and individual actions that can be taken to reduce greenhouse gas emissions.
Ocean warming affects terrestrial climate too
Alban Lazar, a lecturer and researcher in oceanography and climatology at Sorbonne University, observes "alarming" ocean surface temperature data on a daily basis in the LOCEAN-IPSL laboratory in Paris. Despite nearly thirty years of work on the subject, he recalls the shock he felt two years ago during a trip in the Mediterranean. "The readings matched the upper range of scenarios, but it felt like a tipping point," he says.
Since April 2023, temperature curves have been soaring well beyond the norms: the water surface temperature average breaks its monthly record every month. Although it warms slower than continents, the ocean is particularly vulnerable to climate warming because it captures 90% of the excess heat.
Last year, El Niño – a natural and recurring climatic phenomenon – also contributed to the average temperature increase at the water's surface, but it's far from the sole culprit. Record highs are also hitting ocean areas unaffected by El Niño, like the North Atlantic and the Mediterranean.
Beyond their levels, Lazar and other scientists are particularly concerned about the persistence of these high temperatures. On a satellite map, the researcher points out a yellow spot off the coast of Senegal, indicating temperatures 3°C above normal: "We are closely monitoring this area because the water there has been abnormally warm for five years," he explains. "These few degrees are enough to impact local fishing, as certain fish now avoid the area."
He emphasizes: "Ocean warming has consequences on land." This affects food security, as fish account for nearly one-fifth of global protein intake, and also influences weather events. A warmer ocean can, in turn, heat surface air masses and, through complex mechanisms, lead to heavy rainfall episodes. For instance, the warming of the Mediterranean contributed to the torrential rains in Greece, Bulgaria, and Libya in the summer of 2023.
Biodiversity: "I never thought I'd announce the extinction of a species"
Thierry Pérez, research director at the Mediterranean Institute of Biodiversity and Marine and Continental Ecology (IMBE), paints a picture of the underwater landscapes of the Mediterranean. "Imagine animal forests: reefs of multiple colors, fish in impressive quantities," describes Pérez. Yet, marine heatwaves are wiping out entire landscapes, leaving behind nothing but trunks, akin to the aftermath of a wildfire.
After more than 30 years of diving and laboratory research, Pérez still considers himself an "optimist." "Honestly, I never thought I'd announce the extinction of a species," he admits. Yet, that's exactly what happened in a scientific article published in 2023. Following record temperatures in the Mediterranean in the summer of 2022, sometimes up to 5°C above normal at the surface, all bath sponges disappeared between 0 and 20 meters deep, and several other species are on the brink of extinction. These sponges are considered "engineer species," hosting a vast number of species, from worms to mollusks, similar to the red gorgonians, coral relatives whose populations in the Mediterranean are declining.
In this transformation of landscapes, there's what's visible... and then there's the rest. "For years, we've been observing in some species the absence of limbs, size reductions, or mortalities that aren't necessarily visible to the naked eye, even for divers," explains the expert.
For now, the primary damage concerns the first few meters of depth. "The physiognomy of landscapes has been modified over the past two years, but we still have very beautiful, healthy forests," Pérez adds. "There's still time to act: by reducing greenhouse gas emissions and protecting the most fragile ecosystems to avoid additional pressures."
Besides the marine heatwaves showcasing the most impressive temperatures, long-term warming also permanently affects species distribution in the ocean: breeding periods change, invasive species colonize new territories, and disrupt ecosystems. The scientist concludes: "Yet, all these manifestations are invisible, and that's the great tragedy of the ocean."
Plankton: "Parts of the ocean are becoming deserts"
Marina Levy, an oceanographer, research director at the CNRS, and deputy director of the Oceans, Climate, and Resources Department at the Research Institute for Development, reminds us that plankton, despite its microscopic size, constitutes more than 95% of the mass of living beings in the ocean. These microorganisms, mostly invisible to the naked eye, are observable from space thanks to satellites that measure the presence of plant plankton, or phytoplankton. On the images, the richest areas appear as vast green swirls, while the poorer zones are deep blue.
Levy has been studying these photographs for about twenty years. Over the phone, her voice conveys wonder as she recalls 1997, the year the satellite launched that allowed for the study of phytoplankton activity across all oceans. "Our goal was to study its natural variation," she says. "At the time, I couldn't imagine we'd see such clear changes related to warming."
To clarify, the scientist explains the complex mechanics of this microscopic world: phytoplankton needs light to grow, which is why it's found only in the first 150 meters of depth. But it also needs nitrogen, found below. It thrives in areas of vertical currents that allow for water mass exchanges, providing the "food" from the bottom that phytoplankton needs.
However, as surface waters warm, they mix less with the lower layer... Lacking nitrogen, plankton no longer develops in certain areas. While the downward trend is measured on some regional scales, it's still difficult to estimate on a global level. This reduction is partly offset by the resurgence of plankton in the poles, favored by ice melting.
"In the Mediterranean, the downward trend is clear, as it is in the tropical oceans, where areas low in biomass are expanding," Levy notes. "Entire parts of the ocean are becoming deserts." This development is particularly alarming since phytoplankton is at the base of the ocean's food chain, with chain reactions whose full impact is still hard to predict.
Read more at: https://international.la-croix.com/news/environment/ocean-scientists-confront-the-invisible-inferno/19188
By Camille Richir |
February 16, 2024
Month after month, year after year, water surface temperatures are setting new records. As of February 12, 2024, the global average reached 21.1°C, nearly one degree higher than the average from 1980 to 2011. This warming trend extends deep below the surface: the amount of energy absorbed by the oceans has also shattered all previous records, according to two studies published back-to-back in January by the American National Oceanic and Atmospheric Administration and the Chinese Institute of Atmospheric Physics.
To put it in perspective, in 2023, the heat content in the oceans from the surface down to 2,000 meters increased by between 9 and 15 zettajoules—a stark contrast to the annual human energy consumption of 0.5 zettajoule.
Despite these staggering figures, they barely capture the magnitude of the upheaval in this vast body of water that covers 70% of the Earth's surface. How do we narrate a world turned upside down when it remains out of reach for most humans? How do we describe an ocean that "burns" when most of its impacts seem invisible?
In an effort to grasp what's at stake, without claiming to cover every aspect, La Croix spoke to three oceanographers. Through their dives, measurements at sea or from the sky, they stand as sentinels of ocean warming, sharing their concerns about the changes unfolding before their eyes. Yet, they avoid fatalism, emphasizing the collective and individual actions that can be taken to reduce greenhouse gas emissions.
Ocean warming affects terrestrial climate too
Alban Lazar, a lecturer and researcher in oceanography and climatology at Sorbonne University, observes "alarming" ocean surface temperature data on a daily basis in the LOCEAN-IPSL laboratory in Paris. Despite nearly thirty years of work on the subject, he recalls the shock he felt two years ago during a trip in the Mediterranean. "The readings matched the upper range of scenarios, but it felt like a tipping point," he says.
Since April 2023, temperature curves have been soaring well beyond the norms: the water surface temperature average breaks its monthly record every month. Although it warms slower than continents, the ocean is particularly vulnerable to climate warming because it captures 90% of the excess heat.
Last year, El Niño – a natural and recurring climatic phenomenon – also contributed to the average temperature increase at the water's surface, but it's far from the sole culprit. Record highs are also hitting ocean areas unaffected by El Niño, like the North Atlantic and the Mediterranean.
Beyond their levels, Lazar and other scientists are particularly concerned about the persistence of these high temperatures. On a satellite map, the researcher points out a yellow spot off the coast of Senegal, indicating temperatures 3°C above normal: "We are closely monitoring this area because the water there has been abnormally warm for five years," he explains. "These few degrees are enough to impact local fishing, as certain fish now avoid the area."
He emphasizes: "Ocean warming has consequences on land." This affects food security, as fish account for nearly one-fifth of global protein intake, and also influences weather events. A warmer ocean can, in turn, heat surface air masses and, through complex mechanisms, lead to heavy rainfall episodes. For instance, the warming of the Mediterranean contributed to the torrential rains in Greece, Bulgaria, and Libya in the summer of 2023.
Biodiversity: "I never thought I'd announce the extinction of a species"
Thierry Pérez, research director at the Mediterranean Institute of Biodiversity and Marine and Continental Ecology (IMBE), paints a picture of the underwater landscapes of the Mediterranean. "Imagine animal forests: reefs of multiple colors, fish in impressive quantities," describes Pérez. Yet, marine heatwaves are wiping out entire landscapes, leaving behind nothing but trunks, akin to the aftermath of a wildfire.
After more than 30 years of diving and laboratory research, Pérez still considers himself an "optimist." "Honestly, I never thought I'd announce the extinction of a species," he admits. Yet, that's exactly what happened in a scientific article published in 2023. Following record temperatures in the Mediterranean in the summer of 2022, sometimes up to 5°C above normal at the surface, all bath sponges disappeared between 0 and 20 meters deep, and several other species are on the brink of extinction. These sponges are considered "engineer species," hosting a vast number of species, from worms to mollusks, similar to the red gorgonians, coral relatives whose populations in the Mediterranean are declining.
In this transformation of landscapes, there's what's visible... and then there's the rest. "For years, we've been observing in some species the absence of limbs, size reductions, or mortalities that aren't necessarily visible to the naked eye, even for divers," explains the expert.
For now, the primary damage concerns the first few meters of depth. "The physiognomy of landscapes has been modified over the past two years, but we still have very beautiful, healthy forests," Pérez adds. "There's still time to act: by reducing greenhouse gas emissions and protecting the most fragile ecosystems to avoid additional pressures."
Besides the marine heatwaves showcasing the most impressive temperatures, long-term warming also permanently affects species distribution in the ocean: breeding periods change, invasive species colonize new territories, and disrupt ecosystems. The scientist concludes: "Yet, all these manifestations are invisible, and that's the great tragedy of the ocean."
Plankton: "Parts of the ocean are becoming deserts"
Marina Levy, an oceanographer, research director at the CNRS, and deputy director of the Oceans, Climate, and Resources Department at the Research Institute for Development, reminds us that plankton, despite its microscopic size, constitutes more than 95% of the mass of living beings in the ocean. These microorganisms, mostly invisible to the naked eye, are observable from space thanks to satellites that measure the presence of plant plankton, or phytoplankton. On the images, the richest areas appear as vast green swirls, while the poorer zones are deep blue.
Levy has been studying these photographs for about twenty years. Over the phone, her voice conveys wonder as she recalls 1997, the year the satellite launched that allowed for the study of phytoplankton activity across all oceans. "Our goal was to study its natural variation," she says. "At the time, I couldn't imagine we'd see such clear changes related to warming."
To clarify, the scientist explains the complex mechanics of this microscopic world: phytoplankton needs light to grow, which is why it's found only in the first 150 meters of depth. But it also needs nitrogen, found below. It thrives in areas of vertical currents that allow for water mass exchanges, providing the "food" from the bottom that phytoplankton needs.
However, as surface waters warm, they mix less with the lower layer... Lacking nitrogen, plankton no longer develops in certain areas. While the downward trend is measured on some regional scales, it's still difficult to estimate on a global level. This reduction is partly offset by the resurgence of plankton in the poles, favored by ice melting.
"In the Mediterranean, the downward trend is clear, as it is in the tropical oceans, where areas low in biomass are expanding," Levy notes. "Entire parts of the ocean are becoming deserts." This development is particularly alarming since phytoplankton is at the base of the ocean's food chain, with chain reactions whose full impact is still hard to predict.
Read more at: https://international.la-croix.com/news/environment/ocean-scientists-confront-the-invisible-inferno/19188