Chemical concentrations and fluxes from EPICA ice cores EDML and EDC

Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European Project for Ice Coring in Antarctica) deep ice cores. The joint use of these records from opposite sides of the East Antarctic plateau allows for an estimate of changes in dust transport and emission intensity as well as for the identification of regional differences in the sea salt aerosol source. The mineral dust flux records at both sites show a strong coherency over the last 150 kyr related to dust emission changes in the glacial Patagonian dust source with three times higher dust fluxes in the Atlantic compared to the Indian Ocean sector of the Southern Ocean (SO). Using a simple conceptual transport model this indicates that transport can explain only 40% of the atmospheric dust concentration changes in Antarctica, while factor 5-10 changes occurred. Accordingly, the main cause for the strong glacial dust flux changes in Antarctica must lie in environmental changes in Patagonia. Dust emissions, hence environmental conditions in Patagonia, were very similar during the last two glacials and interglacials, respectively, despite 2-4 °C warmer temperatures recorded in Antarctica during the penultimate interglacial than today. 2-3 times higher sea salt fluxes found in both ice cores in the glacial compared to the Holocene are difficult to reconcile with a largely unchanged transport intensity and the distant open ocean source. The substantial glacial enhancements in sea salt aerosol fluxes can be readily explained assuming sea ice formation as the main sea salt aerosol source with a significantly larger expansion of (summer) sea ice in the Weddell Sea than in the Indian Ocean sector. During the penultimate interglacial, our sea salt records point to a 50% reduction of winter sea ice coverage compared to the Holocene both in the Indian and Atlantic Ocean sector of the SO. However, from 20 to 80 ka before present sea salt fluxes show only very subdued millennial changes despite pronounced temperature fluctuations, likely due to the large distance of the sea ice salt source to our drill sites.

针对两根南极冰芯钻探欧洲计划（European Project for Ice Coring in Antarctica, EPICA）的深冰芯，科研团队已获取连续的海盐气溶胶与矿物粉尘气溶胶观测记录。通过联合分析东南极高原两侧的上述记录，可估算粉尘传输与排放强度的变化，并识别海盐气溶胶源区的区域差异。两处冰芯的矿物粉尘通量记录在过去150千年（kyr）中呈现极强的一致性，该特征与冰期时期巴塔哥尼亚粉尘源区的粉尘排放变化密切相关；南大西洋扇区的粉尘通量较南大洋（Southern Ocean, SO）印度洋扇区高出三倍。借助简单的概念性传输模型分析可知，仅大气传输过程可解释南极大气粉尘浓度40%的变化幅度，但实际浓度变化可达5~10倍。由此可见，南极冰期粉尘通量出现显著波动的核心诱因，必然源自巴塔哥尼亚地区的环境变化。尽管南极在倒数第二次间冰期记录到的温度较现代高出2~4℃，但巴塔哥尼亚的粉尘排放（即当地环境条件）在末次冰期与倒数第二次冰期、全新世与倒数第二次间冰期分别高度相似。冰期阶段两处冰芯的海盐通量较全新世高出2~3倍，这一现象难以通过基本稳定的传输强度与遥远的开阔大洋源区得到合理解释。若假设海冰生成为海盐气溶胶的主要源区，且威德尔海夏季海冰的扩张规模显著大于南大洋印度洋扇区，则可轻松解释冰期阶段海盐气溶胶通量的显著增强。在倒数第二次间冰期，我们的海盐记录显示，南大洋印度洋与大西洋扇区的冬季海冰覆盖面积较全新世减少了50%。然而在距今2万至8万年期间，尽管温度波动显著，海盐通量仅表现出极弱的千年尺度变化，这大概率是由于海冰盐源区与本次钻探点位相距过远所致。