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| Titel |
Nutrient utilisation and weathering inputs in the Peruvian upwelling region since the Little Ice Age |
| VerfasserIn |
C. Ehlert, P. Grasse, D. Gutiérrez, R. Salvatteci, M. Frank |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 2 ; Nr. 11, no. 2 (2015-02-10), S.187-202 |
| Datensatznummer |
250117163
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| Publikation (Nr.) |
 copernicus.org/cp-11-187-2015.pdf |
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| Zusammenfassung |
For this study two sediment cores from the Peruvian shelf covering the time
period between the Little Ice Age (LIA) and present were examined for changes
in productivity (biogenic opal concentrations (bSi)), nutrient utilisation
(stable isotope compositions of silicon (δ30Siopal) and
nitrogen (δ15Nsed)), as well as in ocean circulation and
material transport (authigenic and detrital radiogenic neodymium
(ϵNd) and strontium (87Sr/86Sr)
isotopes).
For the LIA the proxies recorded weak primary productivity and nutrient
utilisation reflected by low average bSi concentrations of ~10%,
δ15Nsed values of ~5‰ and intermediate
δ30Siopal values of ~0.9‰. At the same
time, the radiogenic isotope composition of the detrital sediment fraction
indicates dominant local riverine input of lithogenic material due to higher
rainfall in the Andean hinterland. These patterns were most likely caused by
permanent El Niño-like conditions characterised by a deeper nutricline,
weak upwelling and low nutrient supply. At the end of the LIA, δ
30Siopal dropped to low values of +0.6‰ and opal
productivity reached its minimum of the past 650 years. During the following
transitional period of time the intensity of upwelling, nutrient supply and
productivity increased abruptly as marked by the highest bSi contents of up
to 38%, by δ15Nsed of up to ~7‰,
and by the highest degree of silicate utilisation with
δ30Siopal reaching values of +1.1‰. At the
same time, detrital ϵNd and 87Sr/86Sr
signatures documented increased wind strength and supply of dust to the shelf
due to drier conditions. Since about 1870, productivity has been high but
nutrient utilisation has remained at levels similar to the LIA, indicating
significantly increased nutrient availability.
Comparison between the δ30Siopal and δ15Nsed signatures suggests that during the past 650 years the
δ15Nsed signature in the Peruvian upwelling area has to a
large extent been controlled by surface water utilisation and not, as
previously assumed, by subsurface nitrogen loss processes in the water
column, which only had a significant influence during modern times (i.e.
since ~AD 1870). |
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