Large changes in oceanic nutrient inventories from glacial to interglacial periods

Ganeshram, Raja S.; Pedersen, Thomas F.; Calvert, S. E.; Murray, James W.

doi:10.1038/376755a0

Cited by 304 publications

(252 citation statements)

References 24 publications

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“…Broecker [1982] and Ganeshram et al [1995] suggested large changes in oceanic nutrient inventories during glacial time, whereas Boyle [1988] proposed a transfer of nutrients from intermediate waters into deeper waters without changes in the inventory, which requires an increase of alkalinity. The increase in salinity [Broecker, 1982] due to storage of fresh water in ice caps affects both the alkalinity and the total carbon inventory by about 3%.…”

Section: Glacial Ocean Chemistrymentioning

confidence: 99%

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO₂ concentrations

Lefèvre¹,

Watson²

1999

Global Biogeochemical Cycles

113

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Abstract. Iron occurs at very low concentrations in seawater and seems to be a limiting factor for primary production in the equatorial Pacific and the Southern Ocean. The global distribution of iron is still not well understood because of a lack of data and the complex chemistry of iron. We develop a 1 O-box model to study the oceanic distribution of iron and its effect on atmospheric CO2 concentration. Subject to our assumptions, we find that a lack of interocean fractionation of deep sea iron concentrations, as suggested by Johnson et al.[1997a], is not readily explained by a balance of eolian deposition, scavenging, and regeneration. Incorporation of organic complexation in the model, as suggested by Johnson et al., to reduce the scavenging rate of iron when concentrations fall below some ligandstabilized concentration, is one solution to this difficulty. Alternatively, the deep-sea concentration may be more variable than the current, rather sparse data coverage suggests. In the model, deep-sea iron concentrations are responsive to the atmospheric source, even if we adopt stabilization of concentrations by a ligand as modeled by Johnson et al. [1997a]. In the Southern Ocean, where the model suggests iron supply has an important limiting effect on the biota, more than 99% of the iron supply to the surface in the present day comes from upwelling and not from the local atmospheric flux. In the context of glacial-interglacial changes to atmospheric CO2 the model suggests that increasing atmospheric iron to the entire global ocean by a factor of 2, leads to decreases in atmospheric CO2 of 10-30 ppm, depending on assumptions. However, in our model, CO2 concentrations are almost unaffected by changes in Southern Ocean atmospheric fluxes alone, unless these are unrealistically large (> 100 times present day). The effect on atmospheric carbon dioxide is slightly stronger if accompanied by increased stratification of the Southern Ocean. The model suggests that eolian "iron fertilization" of the ocean could have importantly influenced glacial atmospheric CO2 concentrations but that other processes must also be at work to account for the full magnitude of the glacial-interglacial change.

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Section: Glacial Ocean Chemistrymentioning

confidence: 99%

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO₂ concentrations

Lefèvre¹,

Watson²

1999

Global Biogeochemical Cycles

113

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“…Fluxes of barium and organic matter, based on sediment trap data of different oceanic regions have been used to develop algorithms, which link the barium flux to export production (Dymond et al, 1992;Francois et al, 1995;Nürnberg et al, 1997). Solid phase barium -or more precisely biogenic barite -may therefore be used to trace changes in recent and past primary production (e.g., Gingele and Dahmke, 1994;Francois et al, 1995;Ganeshram et al, 1995;Paytan et al, 1996;Ganeshram and Pedersen, 1998;Kasten et al, 2001;Pfeifer et al, 2001). However there are limiting factors which impact on the application of Ba as a productivity tracer.…”

Section: Bariummentioning

confidence: 99%

Geochemical distribution patterns as indicators for productivity and terrigenous input off NW Africa

Plewa

Meggers

Kuhlmann

et al. 2012

Deep Sea Research Part I: Oceanographic Research Papers

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a b s t r a c tOne hundred and twenty-eight surface-sediment samples collected off North-West Africa were studied geochemically to detect the expressions of different meridional climate regimes and zonal productivity gradients in the surface sediments. This geochemical multi-tracer approach, coupled with additional information on the bulk carbonate and TOC contents makes it possible to characterise the sedimentological regime in detail. Typical terrigenous elements like Al, K and Fe mirror the importance of the humid (fluvial) influence in the north of the study area and the dominance of aeolian input in the south. Furthermore, the distributions of Ti and Fe in the surface sediments serve as tracers for the supply of eolian volcanic material from the Canary Islands. The spatial variability of the TOC contents in the surface sediments closely follows the ocean surface productivity patterns, whereas the CaCO 3 contents are mainly controlled by dilution with terrigenous matter. The potential productivity proxy Ba is not a reliable tracer for productivity in this region, since it is mainly supplied by terrigenous input (coupled with aluminosilicates).

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“…Kao (sjkao@gate.sinica.edu.tw) Thus, there is a growing interest in the interaction between climate and N biogeochemistry. Evidence for strong links between climate and key N cycling processes -N 2 fixation and denitrification -has been accumulating (Altabet et al, 1995;Ganeshram et al, 1995;Falkowski, 1997), and several researchers have hypothesized indirect influences of the marine fixed N inventory on paleo-climate (McElroy, 1983;Ganeshram et al, 1995Ganeshram et al, , 2000Pedersen and Bertrand, 2000;Suthhof et al, 2001;Altabet et al, 2002). However, considerable uncertainty still remains regarding changes in global ocean nitrate inventory, particularly during the last glacial period (Deutsch et al, 2004;Altabet, 2007).…”

Section: Introductionmentioning

confidence: 99%

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

et al. 2008

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Abstract. Sedimentary δ 15 N records in two IMAGES cores (MD012404 and MD012403) retrieved from the Okinawa Trough (OT) in the western North Pacific reveal deglacial increases with two peaks occurring during the Bølling/Allerød and the Preboreal/early Holocene periods. These peaks are synchronous with previously reported δ 15 N peaks in the Eastern Tropical North Pacific, although the amplitudes (from 3.8 to 5.8‰) are much smaller in the OT. Similar δ 15 N values for the last glacial maximum and the late-Holocene observed by us at a site far from the present-day zones of water-column denitrification (WCD) indicate that the mean 15 N/ 14 N of nitrate in the upper ocean did not differ much between the two climate states. The accumulation rate of organic carbon and total sulfur content are used as indices of the local WCD potential. The results suggest that enhancement of global WCD rather than local denitrification should be responsible for the deglacial maxima of sedimentary δ 15 N in the Okinawa Trough. Our data could provide additional constraints to better understand changes in nitrogen budget during the glacial to interglacial transition.

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Large changes in oceanic nutrient inventories from glacial to interglacial periods

Cited by 304 publications

References 24 publications

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO₂ concentrations

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO₂ concentrations

Geochemical distribution patterns as indicators for productivity and terrigenous input off NW Africa

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

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Large changes in oceanic nutrient inventories from glacial to interglacial periods

Cited by 304 publications

References 24 publications

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO2 concentrations

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO2 concentrations

Geochemical distribution patterns as indicators for productivity and terrigenous input off NW Africa

North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific

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Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO₂ concentrations

Modeling the geochemical cycle of iron in the oceans and its impact on atmospheric CO₂ concentrations