Scientists recorded two parts of the climate link between the North Atlantic and Antarctica.

Scientists recorded two parts of the climate link between the North Atlantic and Antarctica.

Scientists have recorded two climatic links between the North Atlantic and Antarctica, one is a fast atmospheric passage, and the other is a much slower ocean passage, which led to the rapid climate change in the last ice age-and it may happen again.

In a new study published in Nature this week, an international team of scientists described an extremely sudden climate change event. From 60,000 to 65,438+0,2000 years ago, ocean currents from the ocean strengthened and weakened, and Greenland and Europe sent warm seawater from the tropics into the North Atlantic through the Gulf of Mexico. This ocean current is called Atlantic meridional overturning circulation (AMOC). New research records how the North Atlantic spread these extreme events to Antarctica on the other side of the globe. "The North Atlantic sends information to Antarctica on two different time scales," said Christopher BuEzelle, a climate change expert at Oregon State University and the lead author of the study. "This atmospheric connection is like a short message that will arrive soon, and the ocean connection is more like a postcard, which takes time to arrive-in this case, it takes 200 years. In contrast, the postal service looks good. " "When the North Atlantic warms up because of the strengthening of AMOC, the whole Antarctica will eventually become cold because of the changes in the ocean." It started with the wind, but two centuries later, the ocean brought more influence.

In the last ice age, this AMOC current was usually very weak, dragging the North Atlantic into a cold environment. But researchers say that occasionally it will increase rapidly, leading to a sudden warming in Greenland. Whenever Greenland gets warmer, the climate in Antarctica on the other side of the globe changes twice. The global atmospheric conditions changed immediately, and the westerly wind blowing around the Antarctic was far away from the land, which led to the warming of some parts of the Antarctic and the cooling of some parts. The influence of the second half is much slower, and the cooling effect of the southern hemisphere ocean has not appeared in Antarctica for 200 years.

Justin Weierstein, an atmospheric scientist at Oregon State University, is a co-author of the study. He said that this study explains why the climate of Greenland and Antarctica has not been exactly the same for a long time. "This is the first time you have seen the details of how the climate works on a time scale so clearly, not our meteorological observations," Weierstein said. "It shows us how Greenland and Antarctica are connected in time and space-before people ran around with thermometers to measure the temperature."

In order to rebuild the climate, the researchers examined the ice cores in five different locations in Antarctica and synchronized the dates by observing the volcanic ash layer. They measure the change of temperature by analyzing the ratio of water isotopes. Then, they compared these data with the date of the so-called "Dansgard-Oschiger" event in the Greenland ice core to determine the connection between the two hemispheres. The researchers said that during the last ice age of 654.38 million to 20,000 years ago, these extreme emergencies occurred about 25 times. "When the Gulf Stream reaches its maximum intensity, Greenland will increase its temperature by 65,438+00 to 65,438+05 degrees Celsius in ten years," Bouizett said. "This change is sudden and huge. When the ocean transports heat to the north, the rest of the global ocean begins to get cold. Antarctica finally "noticed" that the ocean was getting cold, but that was 200 years later. Buizert said that the past atmospheric changes in Antarctica have a specific pattern, that is, where it is warmer and where it is colder-this is a temperature fingerprint. Buizert said: "By observing modern observation data, we can find the similarities of what happened in the past, which is really great." "Just like forensic detectives, we can compare the temperature fingerprints of ice cores and modern winds. "That's how we identified the culprit-the westerly wind in the southern hemisphere.

Observations and climate models show that today's AMOC current is weakening due to global climate change, so what happened in the last ice age may happen again. Researchers say that if the past can be used as a guide to future climate change, then the weakening of the Asian monsoon may reduce the intensity of the Asian monsoon, and the livelihood of billions of people will depend on rainfall. The change of wind direction in the southern hemisphere will also reduce the ocean's ability to absorb carbon dioxide, which means that more carbon dioxide emissions will remain in the atmosphere, thus strengthening the greenhouse effect. "We know that our world is warming on average, but regional changes also depend on the response of the atmosphere and ocean circulation," Wettstein said. "Climate models are still divided on this point." This study provides us with a real example of periodic changes in the past, which we can use to test and improve our models.

The researchers warned that besides AMOC, other factors will also affect climate change-the temperature rise caused by greenhouse gases is a major factor in the world, and the change of ozone layer will affect the wind pattern and climate in Antarctica. Bousette has made many scientific expeditions to Antarctica and Greenland. He said that the study "is really exciting for climate geeks like us to figure out how the various parts of the climate are related." He pointed out: "These findings may also have an impact on the future." "Due to global warming and meltwater in Greenland, AMOC is weakening." SMS "is being sent, and atmospheric conditions are changing. Postcards are on their way.