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Orbital and suborbital variations of productivity and sea surface conditions in the Gulf of Alaska during the past 54,000 years: Impact of iron fertilization by icebergs and meltwater
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  • Oscar E. Romero,
  • Leah J. LeVay,
  • Erin L. L. McClymont,
  • Juliane Müller,
  • Ellen A. Cowan
Oscar E. Romero
MARUM - Center for Marine Environmental Sciences

Corresponding Author:[email protected]

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Leah J. LeVay
International Ocean Discovery Program, Texas A&M University
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Erin L. L. McClymont
Durham University
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Juliane Müller
Alfred Wegener Institute
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Ellen A. Cowan
Appalachian State University
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As a high-nutrient and low-chlorophyll region, the modern Gulf of Alaska (GoA) is strongly impacted by the limitation of iron. Paleostudies along the Alaskan slope have mainly focused on reconstructing environmental conditions over the past 18 ka. Based on micropaleontological, biogeochemical and sedimentological parameters, we explore a sediment record covering the past 54 ka at Integrated Ocean Drilling Program Site U1419 to understand the impact of orbital and suborbital-scale climate variability on productivity and sea-surface conditions. Close to the Cordilleran Ice Sheet (CIS), Site U1419 is ideally located to elucidate how the evolution of a large ice mass and glacial processes affected orbital- and suborbital-scale changes in nutrients-(e.g., iron) supply. Meltwater discharge from the northern CIS impacted sea surface dynamics of GoA coastal waters. The corresponding increase in bulk biogenic concentrations during Marine Isotope Stage (MIS) 3 and MIS 2 (54 – 17.3 ka) suggests a direct impact from iron fertilization. Cooling of surface waters played no primary role in the occurrence of primary producers. The inundation of the subaerially exposed continental shelf during the last deglacial (17.3-10 ka) warming could have served as a major micronutrients source. Low productivity after the last deglaciation suggests reduced iron availability. Our multiproxy approach reveals a more complete picture of late Quaternary productivity variations compared to earlier studies along the Alaskan margin. The impact of tidewater glaciers and meltwater discharge on past marine productivity and nutrient budget dynamics of high-latitude coastal regions is discussed.