A significant impetus for recent ocean biogeochemical research has been to better understand the ocean's role as a sink for anthropogenic CO2. In the 1990s the global carbon survey of the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS) inspired the development of several approaches for estimating anthropogenic carbon inventories in the ocean interior. Most approaches agree that the total global ocean inventory of Cant was around 120 Pg C in the mid-1990s. Today, the ocean carbon uptake rate estimates suggest that the ocean is not keeping pace with the CO2 emissions growth rate. Repeat occupations of the WOCE/JGOFS survey lines consistently show increases in carbon inventories over the last decade, but have not yet been synthesized enough to verify a slowdown in the carbon storage rate. There are many uncertainties in the future ocean carbon storage. Continued observations are necessary to monitor changes and understand mechanisms controlling ocean carbon uptake and storage in the future.

Estimation of anthropogenic CO2 inventories in the Ocean

Abstract The Indian Ocean is an important part of the global thermohaline circulation system, receiving deep waters sourced from the Southern Ocean and being the location of upwelling and surface-ocean current flow which returns warm and salty waters to the Atlantic. It is also an ideal location to reconstruct the link between thermohaline circulation and deep-water nutrient contents. No mixing occurs between major deep-water masses along flow paths within the Indian Ocean, so changes in water-mass provenance reflect changes in deep-ocean circulation while nutrient contents reflect addition and dissolution of organic matter. We present neodymium (Nd) and carbon (C) isotope records from an equatorial Indian Ocean core (SK129–CR2) spanning the last 150 kyr. The Nd isotope record shows that an increased proportion of North Atlantic Deep Water (NADW) reached the Indian Ocean during interglacials (Marine Isotope Stages; MIS 1 and 5), and a reduced proportion during glacials (MIS 2, 4, and 6), and also that changes occurred during MIS 3. The magnitude and timing of deglacial and some MIS 3 variability is very similar to those in the RC11–83/TNO57–21 South Atlantic deep Cape Basin Nd isotope record ( Piotrowski et al., 2005 ). Since the deep Cape Basin is oceanographically upstream of the Indian Ocean from a deep water circulation perspective, the Nd isotopes suggest that Atlantic meridional overturning circulation changes were effectively propagated from the southeastern Atlantic into the central Indian Ocean via the Southern Ocean. Comparison of the Nd and C isotope records shows that deep-ocean circulation was decoupled from nutrient-content changes on glacial–interglacial timescales, in particular suggesting higher productivity during MIS 5. Increased equatorial productivity during MIS 5 is supported by benthic infaunal–epifaunal foraminiferal δ 13 C gradients, as well as benthic foraminiferal δ 13 C gradients along deep-water flow. Concurrent warming, indicated by planktonic foraminiferal Mg/Ca during MIS 5 at the site is consistent with changing thermocline temperature and may indicate a link to surface-ocean hydrographic changes.

Indian Ocean circulation and productivity during the last glacial cycle

Abstract Coral reefs constitute real oasis sheltering for about one third of the identified fishes, representing a major advantage for the economy and tourism of many tropical countries. However it is paradoxical to notice that their formation at the cellular level or even at the scale of the organism is still poorly known. Effectively, biomineralisation, the process that is at the basis of their edification, is always the subject of numerous researches. Two combined mechanisms lead to the formation of a biomineral, the synthesis/secretion of macromolecules referred to as ‘organic matrix’, and the transport of ions (calcium, bicarbonates and protons in the case of calcification) to the mineralising site. This review shows a view of the works carried out on biomineralisation in scleractinian corals, including some aspects on the control of calcification by environmental parameters. It also gives insights into the biological basis of the use of coral skeletons as environmental archives in palaeo-oceanography. To cite this article: D. Allemand et al., C. R. Palevol 3 (2004).

Iconographies supplémentaires de l'article : Biomineralisation in reef-building corals: from molecular mechanisms to environmental control

The development of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in 1992 opened up new opportunities for geochemical, mineral exploration, and environmental studies. Recent developments in MC-ICP-MS and its hyphenation to techniques such as laser ablation including femtosecond laser sampling, advances in detection system and several other developments made MC-ICP-MS, one of the most versatile analytical techniques for the determination of isotopic compositions in several types of earth and environmental materials. Different studies in recent times indicated that MC-ICP-MS can routinely produce isotopic data that is similar in precision to those obtainable by secondary ion mass spectrometry (SIMS), sensitive high resolution ion microprobe (SHRIMP), and thermal ionization mass spectrometry (TIMS), with striking advantages such as relatively higher throughputs, ease of analysis as the source operates at atmospheric pressure, and possibility of sample introduction by other means such as laser ablation and chromatographic techniques. Recent studies demonstrate the decisive benefits of MC-ICP-MS analysis (both solution and laser ablation modes) not only isotopic ratio determinations, but also absolute element concentration determinations of several elements in the periodic table in different types of geological and environmental materials in terms of versatility, accuracy, precision and for improved spatial resolution. Laser ablation split stream (LASS) technique with ability to do dating, and capability to obtain isotopic and elemental information simultaneously in rocks and minerals on a single sampling event, when coupled to a second ICP-MS system (typically a quadrupole ICP-MS or a high resolution-ICP-MS) demonstrated its potential to become an important analytical tool in solving important problems, especially in geochemistry. The performance characteristics of MC-ICP-MS are compared with those of other similar analytical techniques such as TIMS, SHRIMP, and SIMS with recent examples. This review contains detailed descriptions of the development of MC-ICP-MS instrumentation, analytical procedures, reference materials, and focused applications in the area of geochemistry, mineral exploration, and environmental areas. 

Recent advances in MC-ICP-MS applications in Earth and environmental sciences: Challenges and solutions

Deep water circulation in the Arabian Sea during the last glacial cycle: Implications for paleo-redox condition, carbon sink and atmospheric CO2 variability

Mohd Tarique

Papers

Deep water circulation in the Arabian Sea during the last glacial cycle: Implications for paleo-redox condition, carbon sink and atmospheric CO2 variability

Reduced Arctic sea ice extent during the mid-Pliocene Warm Period concurrent with increased Atlantic-climate regime

Surface pH Record (1990–2013) of the Arabian Sea From Boron Isotopes of Lakshadweep Corals—Trend, Variability, and Control