Climate-related variations in denitrification in the Arabian Sea from sediment 15N/14N ratios

Altabet, Mark A.; François, Roger; Murray, David; Prell, Warren L

doi:10.1038/373506a0

Cited by 400 publications

(316 citation statements)

References 29 publications

Supporting

Mentioning

296

Contrasting

Unclassified

Order By: Relevance

“…While these insolation conditions were optimal for the development of strong summer and winter monsoons, maximum summer monsoon strength did not develop until 10-8 ka. This time lag between insolation and monsoon strength is consistent with lags observed in several studies of long time-series from the Arabian Sea (Clemens and Prell, 1990;Shimmield et al, 1990;Clemens et al, 1991;Murray and Prell, 1992;Altabet et al;Reichart et al, 1998). This lag has been attributed to a number of different factors, including the timing of maximum cross-equatorial heat transport (Clemens and Prell, 2003, and references therein), changes in the intensity of insolation late in the upwelling season (Reichart et al, 1998), and changes in the position and structure of the Findlater Jet (Anderson and Prell, 1993).…”

Section: Residualsupporting

confidence: 67%

Tropical climate variability from the last glacial maximum to the present

Dahl¹

2005

View full text Add to dashboard Cite

This thesis evaluates the nature and magnitude of tropical climate variability from the Last Glacial Maximum to the present. The temporal variability of two specific tropical climate phenomena is examined. The first is the position of the Intertropical Convergence Zone (ITCZ) in the Atlantic basin, which affects sea surface temperature (SST) and precipitation patterns throughout the tropical Atlantic. The second is the strength of the Indian Monsoon, an important component of both tropical and global climate.Long-term variations in the position of the ITCZ in the Atlantic region are determined using both organic geochemical techniques and climate modeling. Upwelling in Cariaco Basin is reconstructed using chlorin steryl esters as proxies for phytoplankton community structure. We find that the diatom population was larger during the Younger Dryas cold event, indicating that upwelling was enhanced and the mean position of the ITCZ was farther south during the Younger Dryas than it is today. A climate simulation using an ocean-atmosphere general circulation model confirms these results by demonstrating that the ITCZ shifts southward in response to high-latitude cooling.The climate of the Arabian Sea region is dominated by the Indian Monsoon. Results from modern sediments from a suite of cores located throughout the Arabian Sea suggest that wind strength is well represented by the accumulation rate and carbon isotopic composition of terrestrially-derived plant waxes in sediments. Arabian Sea SST patterns, reconstructed from a suite of sediment cores representing four time slices utilizing the Mg/Ca SST proxy, suggest that both the summer and winter monsoons were enhanced 8,000 yr BP relative to today while the summer monsoon was weaker and the winter monsoon stronger at 15,000 and 20,000 yr. These results are confirmed by a time-series reconstruction of SST on the Oman Margin that reveals that SST at this site is sensitive to both regional and global climate processes. The results of this thesis demonstrate that tropical climate, as evaluated by a number of different proxies as well as climate models, has varied substantially over the past 20,000 years and is closely coupled to climate at high-latitudes. sharing ideas, opinions, and enthusiasm. Dan Repeta was the first to offer me the opportunity to come to WHOI and for that opportunity I will always be grateful. This thesis would have taken me double the time if not for the help of many assistants.

show abstract

Section: Residualsupporting

confidence: 67%

Tropical climate variability from the last glacial maximum to the present

Dahl¹

2005

View full text Add to dashboard Cite

show abstract

“…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

View full text Add to dashboard Cite

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.

show abstract

“…Paulmier and RuizPino, 2008), these processes are limited to very low oxygen concentrations and lead to a loss of fixed nitrogen. There is evidence that the intensity of this nitrogen loss has varied in concert with the extension of suboxic waters in the past (Altabet et al, 1995;Ganeshram et al, 2002), and there is concern that ongoing global change may lead to both the recent decline of oxygen levels in the tropical oceans (Stramma et al, 2008) and to a substantial increase in denitrification during this century .…”

Section: Introductionmentioning

confidence: 99%

Stoichiometries of remineralisation and denitrification in global biogeochemical ocean models

2009

View full text Add to dashboard Cite

Abstract. Since the seminal paper of Redfield (1934), constant stoichiometric elemental ratios linking biotic carbon and nutrient fluxes are often assumed in marine biogeochemistry, and especially in coupled biogeochemical circulation models, to couple the global oxygen, carbon and nutrient cycles. However, when looking in more detail, some deviations from the classical Redfield stoichiometry have been reported, in particular with respect to remineralization of organic matter changing with depth or with ambient oxygen levels. We here compare the assumptions about the stoichiometry of organic matter and its remineralization that are used explicitly and implicitly in common biogeochemical ocean models. We find that the implicit assumptions made about the hydrogen content of organic matter can lead to inconsistencies in the modeled remineralization and denitrification stoichiometries. It is suggested that future marine biogeochemical models explicitly state the chemical composition assumed for the organic matter, including its oxygen and hydrogen content.

show abstract

Climate-related variations in denitrification in the Arabian Sea from sediment 15N/14N ratios

Cited by 400 publications

References 29 publications

Tropical climate variability from the last glacial maximum to the present

Tropical climate variability from the last glacial maximum to the present

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

Stoichiometries of remineralisation and denitrification in global biogeochemical ocean models

Contact Info

Product

Resources

About