Flux of ice-rafted detritus in the Fram Strait

A three-year particle flux record from the eastern Fram Strait, between Greenland and Svalbard, revealed a rather untypical seasonal flux pattern compared to other particle flux studies from the Nordic Seas. In the eastern Fram Strait this pattern is characterised by a sudden four- to six-fold increase of the particle flux in January, when no daylight is available to support any biological productivity. Comparison with sea-ice distribution maps led to the conclusion that the sudden increase in the flux is due to ice-rafted detritus released from sea ice, which originated from the Svalbard archipelago and from the northern Barents Sea. Detailed grain size analyses of the silt fraction indicated the >10 µm fraction of the lithogenic matter to be clearly enriched due to IRD input. Even more important is the observation that lithogenic material >40 µm occurs exclusively during the ice-rafting event and, therefore, appears to be a suitable indicator for IRD transported on sea ice. Thus, in addition to coarse IRD (e.g. >500 µm), which is mainly derived from icebergs, the analysis of fine IRD >40 µm in deep-sea sediments can be used to reconstruct paleo-sea-ice extensions.

对格陵兰与斯瓦尔巴群岛之间的弗拉姆海峡东部海域开展的为期三年的颗粒通量观测记录显示，其季节通量模式与北欧海域其他同类颗粒通量研究结果相比，呈现出显著的非典型特征。弗拉姆海峡东部海域的该非典型模式表现为：在全年无日照、无法支撑任何生物生产活动的1月份，颗粒通量会出现4至6倍的突增。通过与海冰分布图对比分析，研究人员得出结论：此次通量突增源自海冰释放的冰筏碎屑（ice-rafted detritus, IRD），这些海冰来源于斯瓦尔巴群岛与巴伦支海北部海域。对粉砂组分开展的详细粒度分析结果显示，受IRD输入的影响，陆源物质中粒径大于10微米的组分出现了显著富集。更为关键的观测结果是：粒径大于40微米的陆源物质仅在冰筏碎屑运移事件期间出现，因此该组分可作为海冰携带IRD的有效示踪指标。据此，除了主要源自冰山的粗粒IRD（如粒径大于500微米的组分）之外，对深海沉积物中粒径大于40微米的细粒IRD开展分析，可用于重建古海冰的分布范围。