Surface- and deep-water hydrography and meltwater events in the mid-latitude North Atlantic Ocean over the past 160,000 years
DOI:
https://doi.org/10.4138/1976Abstract
An investigation involving stable oxygen and carbon isotopes on core Ml5612 from the Mid-Atlantic Ridge (445N, 26°W) shows that distinct negative δIRO anomalies punctuate the plank tonic isotope records and correlate with the ice-raftcd detritus (IRD) events. Within most IRD layers, detntal carbonate contributes between 1 and 13% and supports the contention that the layers are the southern equivalents of the northern North Atlantic Ocean's Heinnch events Anomalies are strongest for the Neogloboquadrina pachyderma (sinistral coiling) isotope record. Systematic changes in the δIRO offset between Globigerina bulloides and Globorotalia inflata signify variations in the mid-latitude thermocline structure. In conjunction with negative benthic δIRC anomalies, the data document a stronger contribution of an IRO-depleted, nutrient-rich water mass during the Heinrich events. The δIRC amplitude of >l% between 25 and 57 ka indicates changes between northern-source (North Atlantic Deep Water) and southern-source (Antarctic Bottom Water) water masses at this site. The Heinrich layers in the mid-latitude core arc correlative with those from a core off Portugal. This synchronicity may have resulted from common changes in a North Atlantic thermohaline switch. RÉSUMÉ Une étude touchanl les isotopes lourds d'oxyéene ct de carbone du noyau M156I2 dc la ride médio-allantique (44=nord. 26° ouest) révéle que des anomalies negatives distinctes de δIRO ponctuent les enregistrements d'isotopes planctoniques et les rapprochent avec des phenomènes d'alimcntation en débris glaciels. La contribution du carbonate délrilique varie entre 1 et 13% a l'inteneur de la majorité des couches de débris glaciels, ce qui conforte la théorie que les couches constituent les équivalents méndionaux des phènoménes de Heinrich septentnonaux de I'Atlantique Nord Les anomalies sont les plus prononcées dans le cas de 1'enregislrcmcnt d'isotopes de Neogloboquadrina pachyderma (enroulement sénestre). Les changements systématiques dans le décalage de δIRO entre le Globigerina bulloides et le Globorotalia inflata témoignent de variations dans la structure de la thermocline de latitude moyenne. Conjointement à des anomalies de δIRO benthiques négatives, les données documenient une contribution plus marquée d'une masse d'eau riche en éléments nutrilifs et a faible tcneur en IRO pendant les phènomèncs de Heinrich. L'amplitude de δIRO de >l% entre 25 el 57 Ka révélent des changements entre les masses d'eau d'origme septentrionale (eaux profondes de l'Atlantique Nord) et d'origine méndronale (eaux dc fond de l'Antartique) en cet emplacement. Les couches de Heinrich du noyau dc latitude moyenne se rapprochent de celles d'un noyau au large du Portugal. Cette synchronicité pourrait découler de changements communs dans une substitution thermohaline de l'Allantique Nord Traduit par la rédactionDownloads
Published
2001-10-01
How to Cite
Park, M.-H., Kiefer, T., & Zahn, R. (2001). Surface- and deep-water hydrography and meltwater events in the mid-latitude North Atlantic Ocean over the past 160,000 years. Atlantic Geoscience, 37(2/3). https://doi.org/10.4138/1976
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