DEFIANT: Drivers and Effects of Fluctuations in sea Ice in the ANTarctic

自工业革命开始以来，大气中的二氧化碳浓度一直在稳步上升。科学家们已经证实，最近北极海冰在夏季的消失直接伴随着人类活动导致的二氧化碳排放量的增加，从20世纪70年代末的约700万平方公里减少到2010年的约350万平方公里。尽管气候模型表明南极海冰的面积也应该随着二氧化碳的增加而减少，但卫星观测表明，1979-2015年间的情况恰恰相反。南极海冰面积的趋势是每十年小幅增加约1.5%。然而，在2016年，海冰面积的急剧减少突然中断了这一增长，而海冰面积远远超出了之前的观测范围。自2016年极端事件以来，南极海冰面积几乎恢复到2016年前的值，突显出南极海冰状况可能从一年发生到下一年的显著变化。海冰的这些变化对整个地球的气候很重要，因为它们影响到冰川南极冰盖的融化，以及南大洋对大气热量和二氧化碳的捕获。最近南极海冰范围的极端波动，以及准确预测、理解和模拟它们的挑战，强调了以下需要：(I)增加我们对驱动南极海冰变化的过程(包括极端事件)的了解，以及(Ii)了解南极海冰在从几周到几十年的不同时间尺度上消失的驱动因素和气候影响。为了解决这一知识差距，需要一个重要的研究计划，这个计划需要进行全年观测，包括整个严寒的南极冬季，并有效地改进最新计算机气候模型中的基本过程。我们的项目名为Defiant(南极海冰波动的驱动因素和影响)，将启动最雄心勃勃的观测活动之一，旨在了解南极海冰的可变性。德国极地考察船Polarstein、英国新极地考察船David Attenborough爵士、英国南极调查局Rothera考察站的科学测量、飞机飞越和卫星将与尖端机器人技术(包括水下机器人Boaty McBoatFaces和一套冰上浮标)无缝合作，为我们提供全面的、全年的大气、海冰和海洋测量。从这些观测中获得的知识将使我们的团队能够开发新的海洋和气候模型，以便更准确地描述南极海冰过程。对这些改进的模型的分析将使我们更好地了解南极海冰突然减少的潜在驱动因素，确定这些极端事件对全球海洋环流的影响，并预测热和二氧化碳通过气候系统移动的影响。通过开发新的观测、新的卫星记录和新的模型，Defiant将在我们对南极海冰系统及其对全球气候的更广泛影响的理解方面取得重大进展。

Since the start of the industrial revolution the CO2 concentration in the atmosphere has steadily risen. Scientists have confirmed that the recent loss of Arctic sea ice in summer directly follows this rise in human-induced CO2 emissions, reducing from about 7 million km2 of Arctic sea ice in the late 1970s to around 3.5 million km2 in the 2010s.While climate models suggest Antarctic sea ice extent should also reduce in response to rising CO2, satellite observations reveal that during 1979-2015 the opposite was in fact true. The trend in Antarctic sea ice extent has been a small increase of approximately 1.5% per decade. In 2016, however, this increase was abruptly interrupted by a dramatic reduction in sea ice extent that was far outside the previously observed range. Since the extreme event in 2016, Antarctic sea ice extent has almost returned to its pre-2016 values, highlighting the significant variability in Antarctic sea ice conditions that can occur from one year to the next. These variations in sea ice are important to the whole Earth's climate, because they affect the melting of the glacial Antarctic Ice Sheet, and the capture of atmospheric heat and CO2 by the Southern Ocean.The recent extreme swings in Antarctic sea ice extent, and the challenge of accurately predicting, understanding and modelling them, emphasise the need to: (i) increase our knowledge of the processes that drive Antarctic sea ice variations, including extreme events, and (ii) understand the drivers and climate implications of Antarctic sea ice loss over different time-scales, from weeks to decades. To address this knowledge gap requires a significant research programme, one that takes year-round observations, including throughout the harsh Antarctic winter, and is effective in improving the underlying processes in the latest computer climate models.Our project, known as DEFIANT (Drivers and Effects of Fluctuations in sea Ice in the ANTarctic), will embark on one of the most ambitious observational campaigns aimed at understanding Antarctic sea ice variability. Scientific measurements from the German research ship Polarstern, the UK's new polar research ship Sir David Attenborough, the British Antarctic Survey's Rothera research station, aircraft overflights and satellites will work seamlessly together with cutting-edge robotic technologies (including the underwater vehicle Boaty McBoatface and a suite of on-ice buoys) to provide us with comprehensive, year-round measurements of atmosphere, sea ice and ocean. The knowledge gained from these observations will enable our team to develop new ocean and climate models in order to more accurately represent Antarctic sea ice processes.The analysis of these improved models will allow us to better understand the underlying drivers of the sudden decrease in Antarctic sea ice, determine the impact of these extreme events on the global ocean circulation, and forecast the implications for the movements of heat and CO2 through the climate system. By developing new observations, new satellite records, and new models, DEFIANT will deliver a major advance in our understanding of the Antarctic sea ice system and its wider impacts on global climate.