Behind the record high temperature in Antarctica
China News Weekly Reporter / Li Xiangtai
Issued in the 943th issue of China News Weekly, 2020.4.13
The overall temperature in Antarctica this summer is higher than the average of previous years, and there has been a record high temperature. On February 7, the National Weather Service of Argentina announced on its official Twitter account that Esperanza, the Argentine research base at the northern tip of the Antarctic Peninsula, set a new record of 18.3 ° C on February 6, exceeding March 2015 A record of 17.5 ° C on the 24th.
On the same day, Claire Nouris, a spokesman for the World Meteorological Organization, said that experts from the World Meteorological Organization will now verify whether this extreme temperature will be defined as a new high-temperature record for the Antarctic continent, the main landmass of the earth. During this process, the weather station on Seymour Island, Antarctica heard another news that the station recorded a high temperature of 20.75 ℃ on February 9.
Data map: Ice surface near Antarctica.
If this data from the Seymour Island Weather Station is confirmed, this will be the first time in the history of Antarctica meteorological observations that temperatures have exceeded 20 ° C.
How does the high temperature of Seymour Island occur?
Li Xichen, a researcher at the Institute of Atmospheric Physics of the Chinese Academy of Sciences, told China News Weekly that in the past three months, the temperature in Antarctica has been higher than the average temperature in the same period in previous years. In fact, this year is indeed the year when the temperature in Antarctica is generally high, but it has not broken the record.
He explained that the two weather stations in Esperanza and Seymour Island are very close to each other, both located at the northern end of the Antarctic Peninsula, with relatively low latitudes. The temperature gap between the Antarctic inland and the peninsula is very large. In summer, the temperature in the peninsula area can reach more than ten degrees Celsius, but the temperature in the inland area is still mostly below zero. Therefore, the temperature of individual weather stations on the peninsula cannot be used to represent the overall temperature of the Antarctic continent.
However, Claire Nullis, a spokesman for the World Meteorological Organization, also pointed out: "The northern Antarctic Peninsula is one of the fastest warming regions on earth, and this region is rapidly warming. Over the past 50 years, the temperature here has risen Nearly 3 ° C. "
The organization said it will study the meteorological conditions surrounding the Antarctic high temperature event, especially whether it is related to the "foehn" weather phenomenon. "Fengfeng" is a common feature of high mountain areas, usually involving strong winds and air at high altitudes that rapidly heat up when descending along slopes or mountain tops due to the obvious difference in air pressure.
In a small area like the Antarctic Peninsula, the topography has a strong influence on temperature. The high temperatures recorded at the two weather stations on the Antarctic Peninsula are the result of the Antarctic warming superimposed on the local circulation and the effect of the wind, and the superimposed coupling of the two warming signals caused a record temperature.
"January and February each year is a period of high temperature in the Antarctic. This time, the smoky wind effect occurred in Seymour Island in early February, so pushing the highest temperature in February is equivalent to pushing the highest temperature throughout the year." Li Xichen Say.
Glacier collapse caused by deeper seawater warming
Ding Yihui, an academician of the Chinese Academy of Engineering and the first director of the National Climate Center, told China News Weekly that on the one hand, climate change in Antarctica is affected by human activities. At the same time, the heat caused by fluctuations in the Pacific Ocean will also affect Antarctic temperatures. Warming is the coupled superposition of natural factors and human activities.
Antarctica is divided into southeastern and southwestern poles, of which the temperature increase occurs more in the southwestern poles. The warming in the Antarctic is mainly caused by natural factors, because the Pacific Ocean facing here has the world's largest warm pool and the most intense warm ocean current. The warming in the Antarctic is mainly affected by human activities. The glaciers in the Antarctic are now melting, but at a slower rate.
Li Xichen said that the Antarctic warming is related to global warming, and the local warming in Antarctica is much faster than the average level of global warming. The average rate of increase in global warming is 0.1 to 0.15 ° C every 10 years, while the winter surface temperature observed at several weather stations in Antarctica from 1980 to 2010 is 3 to 5 ° C. Among them, some weather stations in the Antarctic may reach five times the average level of global warming, and individual stations may even reach ten times the global level in specific seasons and specific time periods. However, the overall warming rate of the Antarctic is relatively slow, and sometimes local areas will also cool down in certain seasons.
Antarctic warming has further led to the melting of Antarctic glaciers. According to the European Space Agency, the Sentinel 1 satellite recorded the apparent collapse of the front of the Songdao glacier in the southwestern pole. The collapse first formed a huge iceberg over 300 square kilometers, with an area approximately equal to the European country Malta. Subsequently, the big iceberg soon split into many small icebergs. Many icebergs floated in Songdo Bay, the largest of which was code-named B-49, and its area was about twice that of Washington, DC. The collapse of the Songdao Glacier ended on February 9-the same day when extremely high temperatures appeared on Seymour Island.
World Meteorological Organization spokesman Claire Nullis pointed out that, as temperatures continue to rise, the annual amount of ice lost by the Antarctic ice sheet has increased at least six times between 1979 and 2017. She warned: "In the past 50 years, about 87% of the glaciers on the west coast of the Antarctic Peninsula have melted, and most of them have accelerated in the past 12 years."
Li Xichen said that the glaciers in the east and southwest poles have very different flow rates, and the main melting of the glaciers in the south pole is in the southwest pole. The two major glaciers in the Antarctic, Songdo and White, and the Totten Glacier, which began to melt faster after 2010, accounted for more than 70% of the total water lost in the Antarctic continent in recent years.
Ding Yihui pointed out that from the perspective of paleoclimatology, historical changes in Antarctic ice sheets are the most important reason for sea level changes. Scientists hope that more than 30 models have been tested based on the coupled ocean hydrological model and climate model. The prediction result is that by the end of this century, sea level will rise by 0.5 ~ 2 meters. But the range of change in this range is still very large, which will cause completely different effects. In order to make the threshold more accurate, the scientists are continuing to study.
Ding Yihui said that apart from China ’s east coast, the east coast of the United States and the Gulf of Mexico, and the Thames in the United Kingdom will be the areas most affected by sea level rise. The United Kingdom is responding to sea level rise by transforming the Thames dam, raising sluices to block flooding, and increasing the height of the bridge.
Northwest China will get wet
Antarctica is often regarded as the “spokesperson” for climate change. In fact, for human beings, global warming is not without harm and without benefit.
In the 1980s, Shi Yafeng, an academician of the Chinese Academy of Sciences, discovered and began to pay attention to the increase in precipitation in northwest China. Accordingly, Shi Yafeng proposed that the climate of northwest China may be transitioning from warm to dry to warm and wet.
Ding Yihui told China News Weekly that the data of the past 40 years confirmed Shi Yafeng's inference that the temperature and precipitation in northwest China have increased in the past 40 years. According to predictions of global climate models, this trend will continue at least until the middle of this century.
According to the results of climate change, scientists have found that the global trend is that “the drier gets drier and the wet gets wetter”, that is, the subtropical regions with less precipitation will become drier, while the middle and high latitudes with more precipitation More and more moist. The area south of the Yangtze River in China belongs to the subtropical zone. Because the area is significantly affected by the monsoon, precipitation is relatively abundant.
However, as subtropical regions of the same latitude around the world are generally drier, the climate change trend in the south of the Yangtze River is also consistent with other subtropical regions. According to the data, in the last 5-15 years, the precipitation in southern China, especially in the Yangtze River Basin, has decreased compared with the past. At present, the precipitation is smaller, but the trend of drought may increase in the future.
The "wet one gets wetter" performance in China is that the precipitation belt is moving northward, and rain will increase in mid-latitudes in North China and Northeast China. Current data has shown that precipitation in Northeast China has increased significantly, as has North China.
On a larger time scale, climate change experienced by humans is an extremely short-term event. Hu Yongyun, a professor in the Department of Atmospheric and Marine Sciences at Peking University, explained that there are three time scales for the climate change of the earth. The largest of these is the geological time scale, which is a change from one million years to ten million years, mainly related to the earth ’s own continental drift and geological activities.
From 250 million years ago to 30 million years ago, the earth was in a very warm state. At this time, the north and south poles did not have ice sheets, and may be covered with lush vegetation. Starting from 30 million years ago, the global temperature dropped, and the ice caps on the north and south poles gradually formed. This is the climate change on the geological time scale.
The cycle of the middle scale is in ten thousand years. Antarctic ice core records indicate that due to changes in the eccentricity of the Earth ’s orbit, the angle of yellow and red, and the precession, the Earth ’s climate has experienced glacial and interglacial cycles with a 100,000-year cycle. When the ice age came, the global low temperature continued and the continental ice sheet extended significantly towards the equator. The interglacial period was between two ice ages, when the global temperature increased and the continental ice sheet melted and receded.
The smallest scale is the millennium scale. Scientists generally believe that climate change on this time scale is related to ocean circulation. Hu Yongyun said that since 12,000 years ago, after the end of the last glacial period, humans are currently in the interglacial period. Adding the factors of human activities, in the long run, global temperatures will continue to warm.
"China News Weekly" No.13, 2020
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