Variations in export production, lithogenic sediment transport and iron fertilization in the Pacific sector of the Drake Passage over the past 400 kyr
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Published:2022-01-27
Issue:1
Volume:18
Page:147-166
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ISSN:1814-9332
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Container-title:Climate of the Past
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language:en
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Short-container-title:Clim. Past
Author:
Toyos María H.ORCID, Winckler Gisela, Arz Helge W., Lembke-Jene LesterORCID, Lange Carina B.ORCID, Kuhn GerhardORCID, Lamy Frank
Abstract
Abstract. Changes in Southern Ocean export production have broad
biogeochemical and climatic implications. Specifically, iron fertilization
likely increased subantarctic nutrient utilization and enhanced the
efficiency of the biological pump during glacials. However, past export
production in the subantarctic southeastern Pacific is poorly documented, and
its connection to Fe fertilization, potentially related to Patagonian Ice
Sheet dynamics, is unknown. We report biological productivity changes over
the past 400 kyr, based on a combination of 230Thxs-normalized and
stratigraphy-based mass accumulation rates of biogenic barium, organic
carbon, biogenic opal and calcium carbonate as indicators of paleo-export
production in a sediment core upstream of the Drake Passage
(57.5∘ S, 70.3∘ W). In addition, we use
fluxes of iron and lithogenic material as proxies for terrigenous input, and
thus potential micronutrient supply. Stratigraphy-based mass accumulation
rates are strongly influenced by bottom-current dynamics, which result in
variable sediment focussing or winnowing at our site. Carbonate is virtually
absent in the core, except during peak interglacial intervals of the
Holocene, and Marine Isotope Stages (MIS) 5 and 11, likely caused by
transient decreases in carbonate dissolution. All other proxies suggest that
export production increased during most glacial periods, coinciding with
high iron fluxes. Such augmented glacial iron fluxes at the core site were
most likely derived from glaciogenic input from the Patagonian Ice Sheet
promoting the growth of phytoplankton. Additionally, glacial export
production peaks are also consistent with northward shifts of the
Subantarctic and Polar Fronts, which positioned our site south of the
Subantarctic Front and closer to silicic acid-rich waters of the Polar
Frontal Zone. However, glacial export production near the Drake Passage was
lower than in the Atlantic and Indian sectors of the Southern Ocean, which
may relate to complete consumption of silicic acid in the study area. Our
results underline the importance of micro-nutrient fertilization through
lateral terrigenous input from South America rather than eolian transport
and exemplify the role of frontal shifts and nutrient limitation for past
productivity changes in the Pacific entrance to the Drake Passage.
Funder
Comisión Nacional de Investigación Científica y Tecnológica Fondo de Financiamiento de Centros de Investigación en Áreas Prioritarias Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research
Publisher
Copernicus GmbH
Subject
Paleontology,Stratigraphy,Global and Planetary Change
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