NOAA/WDS Paleoclimatology - Patriot Hills, West Antarctica Late Glacial Blue Ice Biomarker Data

The Southern Ocean occupies 14% of the Earth's surface and plays a fundamental role in the global carbon cycle and climate. It provides a direct connection to the deep ocean carbon reservoir through biogeochemical processes that include surface primary productivity, remineralization at depth and the upwelling of carbon-rich water masses. However, the role of these different processes in modulating past and future air-sea carbon flux remains poorly understood. A key period in this regard is the Antarctic Cold Reversal (ACR, 14.6-12.7 kyr bp), when mid- to high-latitude Southern Hemisphere cooling coincided with a sustained plateau in the global deglacial increase in atmospheric CO2. Here we reconstruct high-latitude Southern Ocean surface productivity from marine-derived aerosols captured in a highly resolved horizontal ice core. Our multiproxy reconstruction reveals a sustained signal of enhanced marine productivity across the ACR. Transient climate modelling indicates this period coincided with maximum seasonal variability in sea-ice extent, implying that sea-ice biological feedbacks enhanced CO2 sequestration and created a substantial regional marine carbon sink, which contributed to the plateau in CO2 during the ACR. Our results highlight the role Antarctic sea ice plays in controlling global CO2, and demonstrate the need to incorporate such feedbacks into climate-carbon models.

南大洋（Southern Ocean）占地球表面积的14%，在全球碳循环与气候系统中发挥着基础性作用。它通过一系列生物地球化学过程与深海碳储库建立直接联系，这些过程包括表层初级生产力、深海再矿化作用以及富碳水团的上升流。然而，学界对上述各类过程调控过去与未来海-气碳通量的具体机制仍知之甚少。就此而言，南极冷反转（Antarctic Cold Reversal, 简称ACR，14.6~12.7千年前）是关键时段：彼时南半球中高纬度出现降温，同时全球冰消期大气二氧化碳浓度的上升过程出现持续平台期。本研究依托高分辨率水平冰芯中捕获的海源气溶胶，重建了南大洋高纬度海域的表层生产力记录。本研究的多代用指标重建结果显示，在南极冷反转期间，海洋生产力持续处于增强状态。瞬变气候模拟结果表明，该时段海冰范围的季节变率达到峰值，这意味着海冰生物反馈过程强化了二氧化碳固存能力，形成了可观的区域性海洋碳汇，进而推动了南极冷反转期间大气二氧化碳浓度的平台期。本研究结果凸显了南极海冰在调控全球二氧化碳浓度中的关键作用，同时表明气候-碳循环模型有必要纳入此类反馈过程。