The New Technique Shows That Ancient Temperatures Were Much Higher Than We Thought

In a paper recently published in Science, Professor Nele Meckler of the University of Bergen and his colleagues argue that the climate between about 35 and 60 million years ago may have been much warmer than previously thought . Their findings indicate that a given level of CO2 can cause more warming than previous work suggested, and imply that the ocean circulated differently during this warm, ice-free climate. Their conclusions come from new measurements of carbon and oxygen isotopes found in the shells of tiny creatures, called benthic foraminifera, or “foraminifera,” that lived on the sea floor at the time. Previous work with similar samples had estimated temperatures using oxygen isotopes — a technique that could be confounded by changes in how much water was locked in ice at the poles and, to a lesser extent, by variations in ocean salinity. The new study used a technique that records temperatures more reliably and produced much warmer numbers.

A newer, cleaner thermometer

Benthic foramin oxygen isotopes have been a mainstay of ancient global climate studies, with the most recent most detailed record extending back to 60 million years ago. Deep ocean temperatures reflect surface ocean temperatures on time scales longer than about 1,000 years because the global “conveyor belt” of ocean circulation reverses on this time scale. The oxygen isotopes in this water reflect ocean surface temperature, and by extension global climate, because water with the heavier oxygen-18 isotope is slightly more difficult to evaporate than water with oxygen-16. When the sea is warmer and there is more evaporation, oxygen-18 builds up in the oceans. Advertising
This accumulation of isotopes is calibrated to temperature, but this calibration requires knowing the salinity of the oceans and how much water is locked in the ice sheets. “The global [oxygen isotope] The curve … has always had this semi-hidden uncertainty due to the dual influences of temperature and ice volume that we can now resolve using clustered isotopes,” said Sierra Petersen of the University of Michigan, who was not involved in Meckler’s study. . The clustered isotope method removes the need to make this assumption about how much water is locked in the ice because it simultaneously measures the levels of carbon-13 found in the same sample of calcium carbonate in a drill casing. Thermodynamics favors the “clumping” of heavier isotopes into calcium carbonate in cold water, but as the water warms, entropy increasingly exerts its influence and the heavier isotopes become more dispersed in the shell material. The degree of isotope accumulation is temperature-calibrated in the laboratory for a variety of materials, allowing measurements of accumulated isotopes to yield temperature measurements over time. The new method shows that between 57 and 52 million years ago, the North Atlantic abyss was about 20°C. This is a big difference from the oxygen isotope data, which yielded temperatures of 12–14°C. “It’s a lot warmer,” Meckler said. For comparison, today’s equivalent temperature is about 1–2°C.

title: “The New Technique Shows That Ancient Temperatures Were Much Higher Than We Thought Klmat” ShowToc: true date: “2022-12-14” author: “Michael Brown”

In a paper recently published in Science, Professor Nele Meckler of the University of Bergen and his colleagues argue that the climate between about 35 and 60 million years ago may have been much warmer than previously thought . Their findings indicate that a given level of CO2 can cause more warming than previous work suggested, and imply that the ocean circulated differently during this warm, ice-free climate. Their conclusions come from new measurements of carbon and oxygen isotopes found in the shells of tiny creatures, called benthic foraminifera, or “foraminifera,” that lived on the sea floor at the time. Previous work with similar samples had estimated temperatures using oxygen isotopes — a technique that could be confounded by changes in how much water was locked in ice at the poles and, to a lesser extent, by variations in ocean salinity. The new study used a technique that records temperatures more reliably and produced much warmer numbers.

A newer, cleaner thermometer

Benthic foramin oxygen isotopes have been a mainstay of ancient global climate studies, with the most recent most detailed record extending back to 60 million years ago. Deep ocean temperatures reflect surface ocean temperatures on time scales longer than about 1,000 years because the global “conveyor belt” of ocean circulation reverses on this time scale. The oxygen isotopes in this water reflect ocean surface temperature, and by extension global climate, because water with the heavier oxygen-18 isotope is slightly more difficult to evaporate than water with oxygen-16. When the sea is warmer and there is more evaporation, oxygen-18 builds up in the oceans. Advertising
This accumulation of isotopes is calibrated to temperature, but this calibration requires knowing the salinity of the oceans and how much water is locked in the ice sheets. “The global [oxygen isotope] The curve … has always had this semi-hidden uncertainty due to the dual influences of temperature and ice volume that we can now resolve using clustered isotopes,” said Sierra Petersen of the University of Michigan, who was not involved in Meckler’s study. . The clustered isotope method removes the need to make this assumption about how much water is locked in the ice because it simultaneously measures the levels of carbon-13 found in the same sample of calcium carbonate in a drill casing. Thermodynamics favors the “clumping” of heavier isotopes into calcium carbonate in cold water, but as the water warms, entropy increasingly exerts its influence and the heavier isotopes become more dispersed in the shell material. The degree of isotope accumulation is temperature-calibrated in the laboratory for a variety of materials, allowing measurements of accumulated isotopes to yield temperature measurements over time. The new method shows that between 57 and 52 million years ago, the North Atlantic abyss was about 20°C. This is a big difference from the oxygen isotope data, which yielded temperatures of 12–14°C. “It’s a lot warmer,” Meckler said. For comparison, today’s equivalent temperature is about 1–2°C.

title: “The New Technique Shows That Ancient Temperatures Were Much Higher Than We Thought Klmat” ShowToc: true date: “2022-12-04” author: “Lorraine Dunbar”

In a paper recently published in Science, Professor Nele Meckler of the University of Bergen and his colleagues argue that the climate between about 35 and 60 million years ago may have been much warmer than previously thought . Their findings indicate that a given level of CO2 can cause more warming than previous work suggested, and imply that the ocean circulated differently during this warm, ice-free climate. Their conclusions come from new measurements of carbon and oxygen isotopes found in the shells of tiny creatures, called benthic foraminifera, or “foraminifera,” that lived on the sea floor at the time. Previous work with similar samples had estimated temperatures using oxygen isotopes — a technique that could be confounded by changes in how much water was locked in ice at the poles and, to a lesser extent, by variations in ocean salinity. The new study used a technique that records temperatures more reliably and produced much warmer numbers.

A newer, cleaner thermometer

Benthic foramin oxygen isotopes have been a mainstay of ancient global climate studies, with the most recent most detailed record extending back to 60 million years ago. Deep ocean temperatures reflect surface ocean temperatures on time scales longer than about 1,000 years because the global “conveyor belt” of ocean circulation reverses on this time scale. The oxygen isotopes in this water reflect ocean surface temperature, and by extension global climate, because water with the heavier oxygen-18 isotope is slightly more difficult to evaporate than water with oxygen-16. When the sea is warmer and there is more evaporation, oxygen-18 builds up in the oceans. Advertising
This accumulation of isotopes is calibrated to temperature, but this calibration requires knowing the salinity of the oceans and how much water is locked in the ice sheets. “The global [oxygen isotope] The curve … has always had this semi-hidden uncertainty due to the dual influences of temperature and ice volume that we can now resolve using clustered isotopes,” said Sierra Petersen of the University of Michigan, who was not involved in Meckler’s study. . The clustered isotope method removes the need to make this assumption about how much water is locked in the ice because it simultaneously measures the levels of carbon-13 found in the same sample of calcium carbonate in a drill casing. Thermodynamics favors the “clumping” of heavier isotopes into calcium carbonate in cold water, but as the water warms, entropy increasingly exerts its influence and the heavier isotopes become more dispersed in the shell material. The degree of isotope accumulation is temperature-calibrated in the laboratory for a variety of materials, allowing measurements of accumulated isotopes to yield temperature measurements over time. The new method shows that between 57 and 52 million years ago, the North Atlantic abyss was about 20°C. This is a big difference from the oxygen isotope data, which yielded temperatures of 12–14°C. “It’s a lot warmer,” Meckler said. For comparison, today’s equivalent temperature is about 1–2°C.

title: “The New Technique Shows That Ancient Temperatures Were Much Higher Than We Thought Klmat” ShowToc: true date: “2022-11-22” author: “Edward Gantt”

In a paper recently published in Science, Professor Nele Meckler of the University of Bergen and his colleagues argue that the climate between about 35 and 60 million years ago may have been much warmer than previously thought . Their findings indicate that a given level of CO2 can cause more warming than previous work suggested, and imply that the ocean circulated differently during this warm, ice-free climate. Their conclusions come from new measurements of carbon and oxygen isotopes found in the shells of tiny creatures, called benthic foraminifera, or “foraminifera,” that lived on the sea floor at the time. Previous work with similar samples had estimated temperatures using oxygen isotopes — a technique that could be confounded by changes in how much water was locked in ice at the poles and, to a lesser extent, by variations in ocean salinity. The new study used a technique that records temperatures more reliably and produced much warmer numbers.

A newer, cleaner thermometer

Benthic foramin oxygen isotopes have been a mainstay of ancient global climate studies, with the most recent most detailed record extending back to 60 million years ago. Deep ocean temperatures reflect surface ocean temperatures on time scales longer than about 1,000 years because the global “conveyor belt” of ocean circulation reverses on this time scale. The oxygen isotopes in this water reflect ocean surface temperature, and by extension global climate, because water with the heavier oxygen-18 isotope is slightly more difficult to evaporate than water with oxygen-16. When the sea is warmer and there is more evaporation, oxygen-18 builds up in the oceans. Advertising
This accumulation of isotopes is calibrated to temperature, but this calibration requires knowing the salinity of the oceans and how much water is locked in the ice sheets. “The global [oxygen isotope] The curve … has always had this semi-hidden uncertainty due to the dual influences of temperature and ice volume that we can now resolve using clustered isotopes,” said Sierra Petersen of the University of Michigan, who was not involved in Meckler’s study. . The clustered isotope method removes the need to make this assumption about how much water is locked in the ice because it simultaneously measures the levels of carbon-13 found in the same sample of calcium carbonate in a drill casing. Thermodynamics favors the “clumping” of heavier isotopes into calcium carbonate in cold water, but as the water warms, entropy increasingly exerts its influence and the heavier isotopes become more dispersed in the shell material. The degree of isotope accumulation is temperature-calibrated in the laboratory for a variety of materials, allowing measurements of accumulated isotopes to yield temperature measurements over time. The new method shows that between 57 and 52 million years ago, the North Atlantic abyss was about 20°C. This is a big difference from the oxygen isotope data, which yielded temperatures of 12–14°C. “It’s a lot warmer,” Meckler said. For comparison, today’s equivalent temperature is about 1–2°C.