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Fertilization of the ocean by eolian dust and icebergs is an effective mechanism to enhance primary productivity. In particular, high-nutrient, low-chlorophyll (HNLC) areas where phytoplankton growth is critically iron-limited, such as the subarctic Pacific Ocean and the Southern Ocean, are proposed to respond to increases in bioavailable Fe supply with enhanced phytoplankton productivity and carbon export to the seafloor. While Fe-fertilization from dust is widely acknowledged to explain a higher export production during glacial periods in the Southern Ocean, paleoceanographic records supporting links between productivity and eolian dust and/or icebergs in the North Pacific are scarce. By combining independent proxies indicative of ice-sheet dynamics and ocean productivity from a single marine sedimentary record (Integrated Ocean Drilling Program [IODP] Site U1417), we present a comprehensive data set of phytoplankton response to different fertilization mechanisms in the subarctic northeast Pacific between 1.5 and 0.5 Ma, including the Mid Pleistocene Transition. Importantly, the timing of the fertilization events is more strongly controlled by local ice-sheet extent than by glacial-interglacial climate variability. Our findings indicate that fertilization by glacigenic debris results in productivity events in HNLC areas adjacent to ice sheets, and that this mechanism may represent an important, yet rarely considered, driver of phytoplankton growth. [ABSTRACT FROM AUTHOR]

Ground-penetrating radar and luminescence dating studies of a large, complex, linear dune in the northern part of the Namib Sand Sea provide new information on the age and internal sedimentary structures of these dunes, with important implications for interpretations of paleoclimates and the rock record of eolian sandstones. The dune is a composite feature formed during several episodes of construction, including a hiatus of almost 2000 yr. The oldest sands within the dune are 5700 yr old, indicating complete turnover of sand during the Holocene. The dune has moved laterally by ∼300 m during the past 2500 yr, proving lateral migration of a large linear dune. Dune construction has been affected by climate change, and we attribute the hiatus to increased rainfall and vegetation, which largely halted sand movement and dune building in the Namib Desert during the middle Holocene. [ABSTRACT FROM AUTHOR]