3万年以来挪威海南部冰岛-苏格兰溢流变化及其对海冰活动的响应

北欧海南部沉积物所记录的末次冰盛期以来千年尺度快速气候事件下的溢流水变化特征,对研究历史上热盐环流与气候的相互作用机制有着重要意义.本文基于冰岛东北部陆架IS-1B岩芯(65°36.357′N, 8°59.045′W)上部130 cm的沉积物粒度组成、颜色反射率和高分辨率XRF元素地球化学扫描测试数据,结合有孔虫AMS 14C测年数据和邻近海区站位沉积资料,利用因子分析等方法,重建了研究区3万年(HS 3期)以来的沉积记录,并重点研究了冰岛-苏格兰溢流水(ISOW)的历史变化特征及其对海冰活动的响应.研究结果显示, ISOW在末次冰盛期初期、 HS1末期到 B/A 暖期和全新世时期强度较高,在HS 3期末期、末次冰盛期中后期到HS 1初期和YD时期强度较弱,其中粒度和地球化学证据都指示ISOW在末次冰盛期和YD时期受北冰洋底层水入侵和海平面下降的影响可能发生了多次停滞.总体来说,挪威海南部ISOW强度的变化与表层海水温度有较强的相关性,表现为冰期减弱,间冰期增强的变化趋势.挪威海北部海冰的覆盖范围自HS 3末期至末次冰盛期开始逐渐南移,并在HS 2初期越过冰岛-苏格兰海脊,在冰岛海盆北部形成常年的冰覆盖. HS 1期中后期到B/A暖期,海冰影响范围开始逐渐下降,但在 B/A 暖期末期到YD时期海冰活动便快速恢复,直至进入全新世后,挪威海南部海冰活动强度才逐渐下降,一直保持相对稳定的季节性海冰活动状态.

Changes of Iceland-Scotland Overflow Water in Southern Norwegian Sea and the responses to sea ice activities since 30ka B. P.

The Southern Norwegian Sea sediments record the characteristics of overflow water which experienced the rapid millennium scale climatic events since 31 ka and play a critical role in studying the interaction between thermohaline circulation and climate in history. The gravity core IS-1B (65°36.357'N, 8°59.045'W) recovered from the Northeast shelf of Iceland is mainly composed of yellow-brown clay with uniform lithology and bioclastic. The core's samples were soft with strong viscosity, and was analyzed to reconstruct the sedimentary record, based on the AMS14C data of foraminifers in the top 130 cm (the full length of core IS-1B is 630 cm) combined with the grain size composition, color reflectance, high-resolution XRF scanning. Meanwhile, factor analysis was used to extract the signals of overflow and sea ice transport from the particle size data and element geochemistry data, combining with the research of biological productivity, salinity and REDOX environment characteristics, to reveal the Iceland-Scotland Overflow Water (ISOW) changes and its response to the sea-ice activities from 31 ka to the Late Holocene. The results show that ISOW is strongly affected by the invasion of the Arctic Bottom Water and the sea level drop in the Last Glacial Maximum and the YD period, and even stopped. However, biological productivity and oxidation-deoxidation characteristics all indicate that ISOW is relatively strong during the B/A warm period, late HCO and middle to late Holocene. And the overall trend is that the glacial period decreases and the interglacial period increases. As for the sea ice cover in the northern part of the Norwegian sea, it gradually moved southward from the late stage of HS3, and crossed the Iceland-Scotland Ridge in the early HS2, forming perennial ice cover in the northern part of the Icelandic basin. From HS1 to B/A warm period, sea ice extent began to decline gradually, but recovered rapidly from the end of B/A warming period to YD period. At last the sea ice activity decreased slowly during the Holocene and became the seasonal sea ice activity.