Arctic-Tropical Teleconnections in the climate system (ArcTrop)

持续不断的气候变化伴随着大气、海洋、回旋体和陆地表面条件的快速、部分混乱的变化，这些变化不仅影响气温，而且影响水文循环、海冰和冰盖、海平面、包括沿海洋流在内的海洋环流。虽然观测技术能够在人为强迫下对气候系统进行高分辨率的空间和时间监测，但系统的“前人类”状态和自然变异性为探索气候系统在极端条件下的行为提供了机会，无论是比现在更暖或更冷的条件，以及在诸如导致撒哈拉荒漠化的重要过渡期间，直到大约6,000-5,000年前，撒哈拉一直被各种植被覆盖。在这里，我们旨在研究北极和热带气候之间潜在的相互反馈。我们将结合气候和不同复杂性的强迫海洋模型模拟和古气候档案，深入研究导致全球海平面上升120米的最后一次冰川消融的快速冰川融化阶段，以及大约11,700年前开始的当前间冰期。在所关注的时间间隔内，北极和热带地区的区域和半球尺度上都不时出现突然的气候变化，例如，年轻的仙女木(12 900-11 700年前)伴随着西欧接近8摄氏度的降温，以及非洲湿润时期(14 500-5 000年前)撒哈拉草原森林植被的开始和消失。这些事件的发生速度远远快于所强调的外部强迫(太阳辐射的变化)，不仅突出了气候系统中关键临界点的存在，而且还暗示了高纬度和低纬度之间的潜在反馈。因此，在这方面，通过将建模和古气候数据结合起来，该项目的总体目标是揭示北极和热带之间的主要远场联系，因为它们可以在放大高纬度的气候变化和冰融化以及改变低纬度的季风降水和干旱方面发挥关键作用。

Ongoing climate change is accompanied by rapid, partly chaotic, variations in atmospheric, ocean, cyrospheric and land surface conditions that affect not only air temperature, but also the hydrological cycle, sea ice and ice sheets, sea level, ocean circulation including coastal currents. While observation techniques allow high resolution spatial and temporal monitoring of the climate system under anthropogenic forcing, the "pre-anthropogenic" state and natural variability of the system offer the opportunity to explore the behavior of the climate system under extreme conditions, warmer or colder than present, and during important transitions such as the one that led to the desertification of the Sahara, which was covered by a diverse vegetation until about 6,000-5,000 years ago. Here we aim at investigating potential mutual feedbacks between Arctic and tropical climate. We will use a combination of climate and forced ocean model simulations of different complexity and paleoclimate archives to delve into the rapid ice melting phase of the last deglaciation that led to > 120 m global sea-level rise and the current interglacial period that started about 11,700 years ago. The time interval of interest has been punctuated by abrupt climate change at regional as well as hemispheric scale both in the Arctic and in the tropical regions, like for example the Younger Dryas (12,900 - 11,700 years ago) that was accompanied by cooling close to 8°C in western Europe and the inception and withdrawal of the steppe-forest vegetation in the Sahara during the African Humid Period (14,500 - 5,000 years ago). These events occurred at a pace much faster than the underlining external forcing (changes in solar insolation) not only highlighting the presence of critical tipping points in the climate system but also suggesting potential feedbacks between high and low latitudes. Hence, in this context, by combining modeling and paleoclimate data, the overall goal of this project is to unravel key far-field connections between the Arctic and tropical latitude as they could play a key role in amplifying climate change and ice melt at high latitudes, and in altering monsoonal precipitation and droughts at low latitudes.