Impact of paleoclimatic and paleoceanographic changes on the stability of the late Miocene to present West Antarctic Ice Sheet

古气候和古海洋变化对中新世晚期至今南极西部冰盖稳定性的影响

• 批准号: 528400537
• 负责人: Professor Dr. Thorsten Bauersachs
• 金额: --
• 依托单位: Lehrstuhl für Organische Biogeochemie in Geo-Systemen (OBG)
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/528400537?language=en
• 关键词: Impact; paleoclimatic; paleoceanographic; changes; stability

West Antarctica is the fastest melting region of the Antarctic continent and the West Antarctic Ice Sheet (WAIS) currently contributes about 90% to the total ice loss. The unique geological setting with a landward dipping shelf in combination with the upwelling of warm circumpolar deep water (CDW) that is trapped below the ice sheet, which is grounded several hundred meters below sea level, results in increased basal melting and is considered primarily responsible for the rapidly accelerating ice loss observed in West Antarctica over the recent past. There is particular concern that this process - within two to three decades after initiation - is irreversible and will result in the partial to full collapse of the WAIS within the next centuries. Given that the WAIS holds about 10% of Antarctica’s ice volume, this will equal a global sea level rise of 3.3 to 4.3 m. While recent instrumental and satellite-derived observations clearly demonstrate that the WAIS is particularly vulnerable to rapid melting, proxy records that can be employed to (1) establish causal and temporal links between the upwelling of warm CDW and ice sheet melting and (2) ground truth model simulations of ice sheet advances and retreats under different climate scenarios are entirely missing from this most vulnerable region of our planet. Sediments recovered during IODP Expedition 379 "West Antarctic Ice Sheet History" can close this gap. They provide the first continuous and undisturbed sedimentary sequence, spanning the late Miocene to present, from the continental rise of the Amundsen Sea; an area that is most strongly affected by ice melting and key to investigate the WAIS history. The here proposed project will, for the first time, investigate the complex interplay between paleoclimatic and paleoceanographic changes in West Antarctica and their impetus for the ice sheet dynamic of the WAIS using a multi-proxy approach consisting of bulk-geochemical and lipid biomarker investigations that are complemented by the application of organic temperature proxies. Specifically, the project will establish the first long-term paleotemperature record from the West Antarctic (covering the past ~6.8 Ma), which will allow a differential comparison of West Antarctic climate variability with those of other Antarctic regions. Through high-resolution studies of intervals considered to have experienced a partial to full collapse of the WAIS, including the mid-Pliocene Warm Period and Marine Isotope Stage 31, the project will also provide first temporal constraints on the velocity and extent of ice sheet retreat in response to climate warming and/or the upwelling of CDW onto the Amundsen Sea shelf. The here proposed research will thus provide important new insights into the climate and ice sheet dynamics of an area of the Antarctic continent that is most susceptible for ice sheet loss but for which rates and magnitudes of ice loss are largely terra incognita.

南极洲西部是南极大陆融化最快的地区，南极西部冰盖（WAIS）目前约占总冰损失的90%。独特的地质环境，包括一个向陆地倾斜的大陆架，加上被困在海平面以下数百米的冰盖之下的温暖的环极深水（CDW）的上涌，导致基底融化增加，并被认为是最近在西南极洲观测到的冰损失迅速加速的主要原因。特别令人关切的是，这一进程- -在启动后的二、三十年内- -是不可逆转的，并将导致西海生态系统在今后几个世纪内部分或完全崩溃。考虑到西洋带的冰量约占南极洲冰量的10%，这将相当于全球海平面上升3.3至4.3米。虽然最近的仪器和卫星观测清楚地表明，WAIS特别容易受到快速融化的影响，但可以用来(1)建立温暖的CDW上升流与冰盖融化之间的因果关系和时间联系的代理记录，以及(2)在不同气候情景下冰盖推进和退缩的地面真值模式模拟，在我们星球上这个最脆弱的地区完全缺失。IODP 379考察队“南极西部冰原史”期间回收的沉积物可以弥补这一差距。它们提供了第一个连续的、不受干扰的沉积序列，从晚中新世到现在，从阿蒙森海的大陆隆起开始；这是一个受冰融化影响最强烈的地区，也是研究WAIS历史的关键。本文提出的项目将首次使用多代理方法，包括体积地球化学和脂质生物标志物调查，并辅以有机温度代理的应用，研究西南极洲古气候和古海洋变化之间的复杂相互作用及其对WAIS冰盖动力学的推动作用。具体而言，该项目将建立南极西部的第一个长期古温度记录（覆盖过去~6.8 Ma），这将使南极西部的气候变率与南极其他地区的气候变率进行差异比较。通过高分辨率的研究，包括上新世中期暖期和海洋同位素阶段31，该项目还将首次提供冰盖退缩的速度和程度的时间限制，以响应气候变暖和/或CDW上涌到阿蒙森海大陆架。因此，这里提出的研究将为南极大陆一个地区的气候和冰盖动力学提供重要的新见解，该地区最容易受到冰盖损失的影响，但其冰损失的速度和幅度在很大程度上是未知的。