Was Subantarctic Dust a Major Driver of Past CO2 Variability?

智力优势：海水中铁的稀缺会限制全球海洋中主要营养物浓度高但浮游植物生长低的地区从表层向深水出口的碳量。其中，南大洋是铁含量变化对地球影响最大的地区。美国碳循环通过其对海洋生态系统的施肥作用。PIs建议在亚南极太平洋的五个地点测量生物生产力和尘埃通量，其中包括一个高分辨率地点，以重建这些参数在突变气候变化事件中的变动性。这些重建将使pi能够测试亚南极太平洋的尘埃通量变化和生物生产力变化是否与亚南极大西洋相关。如果确实如此，结果将支持目前对铁施肥对降低二氧化碳的影响的估计。然而，如果他们没有在南太平洋发现铁施肥的证据，那么铁施肥对冰期二氧化碳循环的估计影响必须减少，而其他与铁施肥无关的过程将需要被引用来解释较低的冰川二氧化碳水平。这项研究的结果可能会改变人们对南大洋在调节大气二氧化碳中的作用的认识。更广泛的影响：该项目将促进强有力的国际合作，并将培养一名博士后研究员和两名本科生。这项研究将评估过去对南大洋最大区域铁输入的自然变化的反应。

Intellectual Merit: The scarcity of iron in seawater can limit the amount of carbon exported from surface to deep waters in areas of the global ocean where the concentration of major nutrients is high, yet phytoplankton growth is low. Of these, the Southern Ocean is the region where variations in iron availability have the largest effect on Earth?s carbon cycle through its fertilizing effect on marine ecosystems. The PIs propose to measure biological productivity and dust flux at five sites spanning the breadth of the Subantarctic Pacific, including one high-resolution site to reconstruct variability of these parameters across abrupt climate change events. These reconstructions will allow the PIs to test whether or not variations in dust flux and changes in biological productivity are correlated in the Subantarctic Pacific as they are in the Subantarctic Atlantic. If they are, results will support current estimates of the iron fertilization effect on lowering CO2. However, if they do not find evidence for iron fertilization in the South Pacific, then the estimated impact of iron fertilization on ice-age CO2 cycles must be reduced and other non- iron fertilization related processes would need to be invoked to account for lower glacial CO2 levels. The results of this study could transform understanding of the role of the Southern Ocean in regulating atmospheric CO2.Broader impacts: This project will foster a strong international collaboration and will train a postdoctoral researcher and two undergraduate students. This research will assess the past response to natural variability of iron input in the largest sector of the Southern Ocean.