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Circulación profunda del Atlántico Norte durante los últimos 200.000 años: evidencia geoquímica
Science (New York, N.Y.)
|November 19, 1982
Resumen
Las conchas fósiles revelan los niveles de nutrientes de las aguas profundas del Atlántico Norte durante más de 200.000 años. El suministro de agua empobrecida de nutrientes disminuyó durante las glaciaciones, lo que sugiere un carbono continental menos variable.
Área de la Ciencia:
- La paleoceanografía es la paleoceanografía.
- La geoquímica marina es la geoquímica marina.
- Estudios de las foraminiferas.
Sus antecedentes:
- Las relaciones cadmio/calcio en las conchas bentónicas de foraminíferos reflejan la composición de las aguas profundas del Atlántico Norte (NADW).
- La distribución del cadmio oceánico refleja la distribución de los nutrientes, por lo que Cd/Ca es un proxy de los niveles de nutrientes pasados.
- Comprender el papel de NADW en el ciclo de nutrientes es crucial para las reconstrucciones climáticas.
Objetivo del estudio:
- Para reconstruir las variaciones temporales en la distribución de nutrientes en el Atlántico Norte durante los últimos 200.000 años.
- Para evaluar la influencia de las glaciaciones en el contenido de nutrientes de NADW.
- Para evaluar la variabilidad del inventario de carbono continental.
Principales métodos:
- Análisis de las proporciones de cadmio/calcio en las conchas fósiles de foraminíferos bentónicos de un núcleo de sedimentos del Atlántico Norte.
- Utilizando datos de núcleos de sedimentos que abarcan los últimos 200.000 años.
- Integración de los datos de isótopos de carbono.
Principales resultados:
- Se identificó un suministro continuo de aguas empobrecidas de nutrientes en las profundidades del Atlántico Norte en los últimos 200.000 años.
- La contribución de esta fuente empobrecida de nutrientes disminuyó en aproximadamente un 50% durante los períodos glaciales severos.
- Los datos de cadmio/calcio indican un inventario de carbono continental menos variable de lo que se suponía anteriormente.
Conclusiones:
- Las relaciones Cd/Ca de Benthic foraminifera proporcionan un registro robusto de las variaciones pasadas de nutrientes en el Atlántico Norte.
- Los períodos glaciales alteraron significativamente el equilibrio entre las masas de agua empobrecidas y enriquecidas en nutrientes en el Atlántico Norte.
- El estudio desafía las suposiciones anteriores sobre la magnitud de las fluctuaciones del inventario de carbono continental durante los ciclos glacial-interglacial.
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