在上一次冰川消融期间，南大洋在大气中二氧化碳的快速增加中发挥了关键作用,000 to 10,000 years ago, according to a new report 由电子游戏软件地球化学家王星辰(Tony)和一个国际团队在 Science Advances.
In this new study, Wang and his coauthors analyzed deep-sea coral fossils from 20,000 to 10,000 years ago, when atmospheric carbon dioxide was on the rise.
通过检查珊瑚化石中氮和碳的化学特征, 电子游戏正规平台人员发现，由于浮游植物无法吞噬南大洋上升流提供的大量营养物质，并将二氧化碳困在深海中，海洋碳固存能力下降. 由于人类活动(主要是化石燃料的消耗)导致大气二氧化碳水平上升，这一发现引发了人们对海洋吸收人为二氧化碳的能力及其环境后果的质疑, including global warming, rising sea levels, and more frequent wildfires, according to Wang.
BC researcher Tony Wang
自工业革命以来人类活动所排放的二氧化碳, roughly 50 percent stayed in the atmosphere, 大约四分之一被海洋吸收，大约25%被陆地生态系统隔离. To better predict the fate of anthropogenic carbon dioxide in the future, 王和他的合作者们电子游戏正规平台了在任何重大人类活动之前大气中二氧化碳的变化, from 20,000 to 10,000 years ago when the Earth was moving out of the last ice age.
“对过去二氧化碳变化的更清晰的了解，为未来人为二氧化碳的命运提供了重要的见解,” said Wang, 地球与环境科学系的助理教授, who also holds a courtesy appointment to the Department of Chemistry.
By studying air bubbles trapped in ancient ice from Antarctic, 科学家们了解到，在冰河时期，大气中的二氧化碳浓度比工业化前的水平低了大约30%. 这种较低的二氧化碳水平促使北美大冰原的生长，并使冰河时代的地球降温. However, 关于为什么二氧化碳浓度在冰河时期较低一直存在激烈的争论. In a previous study led by Wang, 他发现了强有力的证据，表明南大洋是冰河时期二氧化碳浓度降低的主要原因.
The remotely-operated vehicle used to collect deep-sea corals.
Phytoplankton growth in the ocean, supported by macronutrients nitrogen and phosphorus, 从大气中吸收二氧化碳并将其转化为有机碳. When these organisms die, 它们的生物量沉入深海并分解成二氧化碳.
This process, called the “biological pump,将二氧化碳从大气和海洋表面转移到黑暗中, deep ocean. In most parts of the modern ocean, 浮游植物消耗了提供给阳光照射的海洋的所有营养物质，“生物泵”达到了最高效率. However, in the Southern Ocean, phytoplankton growth is limited by the supply of the key nutrient iron, as well as sunlight. As a result, large amounts of nitrogen and phosphorus remain in this ocean region, 代表着浪费了大气中二氧化碳封存的机会.
By analyzing the isotopic composition of nitrogen in deep-sea coral fossils, 王发现，在最后一个冰河时期，南大洋的生物泵效率更高, 从大气中吸收更多的二氧化碳，从而降低大气中二氧化碳的浓度.
Nitrogen has two stable isotopes, Nitrogen-14 and Nitrogen-15, with Nitrogen-15 representing approximately 0.4 percent of the total nitrogen atoms in nature. 天然样品中氮-15和氮-14比例的微小变化包含了有关海洋中氮循环的有用信息. For example, when phytoplankton assimilates nitrogen to build their biomass, they prefer Nitrogen-14 to Nitrogen-15, leaving behind nitrogen that is enriched in Nitrogen-15.
Wang之前开发了一种高度敏感和精确的方法，用质谱仪测量珊瑚骨架中氮同位素的比例. 这种能力使他能够测量来自南大洋的深海珊瑚化石中氮的同位素组成.
“Deep-sea corals are a wonderful archive for studying the ocean’s history. You can find them in a lot of places in the deep ocean. And their ages can be known very precisely using radiometric dating methods,” said Nanjing University’s Tao Li, first author of the new study, 题为“在冰期碳循环事件期间南大洋环流和生物地球化学的快速变化”."
Ancient pieces of coral—species Desmophyllum dianthus—used in the study.
In this new study, Wang and his coauthors focused on well-dated deep-sea coral fossils from 20,000 to 10,000 years ago, 当大气中的二氧化碳从冰河时代的水平上升到工业化前的水平. 深海珊瑚化石的精确年代使得直接比较南大洋的变化与南极冰芯的二氧化碳记录成为可能.
“If you look closely at the carbon dioxide record during the deglaciation, you will see that there are a few sudden jumps,” said Wang. “在100到200年的时间里，每一次跳跃都是百万分之10-15的二氧化碳增加. That’s pretty fast but we didn’t quite understand why these jumps happened.”
The new data from deep-sea coral fossils, including nitrogen isotopes and radiocarbon, 表明南大洋也是二氧化碳快速跳跃的主要原因,000-10,000 years ago. When these rapid carbon dioxide changes happened, 南大洋的生物泵效率较低，而南大洋的通风速度更快, the study found.
“However, 应该指出的是，目前人为增加的二氧化碳至少比上次冰川消融期间自然快速增加的二氧化碳快10倍. We are changing our planet at an unprecedented rate,” said Wang.
Wang joined BC last year, 在完成了普林斯顿大学的博士学位和加州理工学院的博士后培训之后. 他计划利用深海珊瑚继续电子游戏正规平台过去大气中二氧化碳的变化.
王说:“使用遥控车辆收集深海珊瑚是非常令人兴奋的。. “We plan to go to the Brazil margin for the next phase of our research.”
Ed Hayward | University Communications | November 2020