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

Winter westerly disturbances (WWD) are the primary climatic influence within High Mountain Asia during the boreal winter. Here we investigate variations and changes in WWD over the period 1979–2010 and relationships with heavy (85th percentile) precipitation in the Karakoram/western Himalaya (KH) and central Himalaya (CH) using multiple datasets. We show that heavy precipitation events occurring in the KH and CH are often spatiotemporally independent, suggesting differing behavior of WWD affecting each region. The wavelet power spectrum of 200 hPa geopotential height anomalies is used to characterize the frequency and magnitude of individual disturbances and to distinguish synoptic scale variability through time. Our analysis exhibits an enhancement in the strength and frequency of WWD in the KH and indicates an increase in local heavy precipitation events. In contrast, the CH is observed to experience weakening influence of these disturbances and consequently, a decrease in heavy precipitation. Furthermore, we investigate multi-annual variability of WWD and teleconnections with some known modes of climate variability affecting central Asia, including the Arctic Oscillation, Eurasian/Polar Pattern, the El Nino Southern Oscillation, and the Siberian High. Although there is clear evidence that these modes affect circulation and precipitation in High Mountain Asia, their competing influences on WWD are complex and non-linear. These results suggest that a thorough understanding of WWD and their spatiotemporal variations are crucial to improve our knowledge of the hydrologic cycle within High Mountain Asia as well as our ability to project the future status of Asia’s water resources.

Multi-Annual Variations in Winter Westerly Disturbance Activity Affecting the Himalaya

. This paper revisits the knowledge on the residence time of water in the atmosphere. Based on state-of-the-art data of the hydrological cycle we derive a global average residence time of 8.9 ± 0.4 days (uncertainty given as 1 standard deviation). We use two different atmospheric moisture tracking models (WAM-2layers and 3D-T) to obtain atmospheric residence time characteristics in time and space. The tracking models estimate the global average residence time to be around 8.5 days based on ERA-Interim data. We conclude that the statement of a recent study that the global average residence time of water in the atmosphere is 4–5 days, is not correct. We derive spatial maps of residence time, attributed to evaporation and precipitation, and age of atmospheric water, showing that there are different ways of looking at temporal characteristics of atmospheric water. Longer evaporation residence times often indicate larger distances towards areas of high precipitation. From our analysis we find that the residence time over the ocean is about 2 days less than over land. It can be seen that in winter, the age of atmospheric moisture tends to be much lower than in summer. In the Northern Hemisphere, due to the contrast in ocean-to-land temperature and associated evaporation rates, the age of atmospheric moisture increases following atmospheric moisture flow inland in winter, and decreases in summer. Looking at the probability density functions of atmospheric residence time for precipitation and evaporation, we find long-tailed distributions with the median around 5 days. Overall, our research confirms the 8–10-day traditional estimate for the global mean residence time of atmospheric water, and our research contributes to a more complete view of the characteristics of the turnover of water in the atmosphere in time and space.

The Residence Time of Water in the Atmosphere Revisited

Integrating multiproxy results (geochemistry, mineral magnetism, grain size, and C/N ratio variability supported by 14C AMS dating), obtained from a 1.4-m sediment core retrieved from high-altitude...

Paleoenvironmental shifts spanning the last ~6000 years and recent anthropogenic controls inferred from a high-altitude temperate lake: Anchar Lake, NW Himalaya:

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

Anchar Lake, a mono-basined freshwater lake in Kashmir Valley, has experienced major sediment deterioration due to changes in the local catchment and anthropogenic inputs during the recent past. The present study was conducted to evaluate the major, trace element concentrations and environment risk assessment in the surface sediments of Anchar Lake. Spatial distribution of organic matter (OM), CaCO3, TOC, sand–silt–clay and C/N ratio was studied to understand their source and accumulation in recent surface sediments. Textural studies indicate that most of the sediment samples are clayey silt to silty clay except one sample being of sandy–clay–silt nature. OM, CaCO3 content and C/N ratio results reveal that the sediments are organically rich and the source of OM is controlled by both; autochthonous and terrestrial sources. The major oxide geochemistry reflects higher concentrations of CaO, MgO and TiO2 compared to the  UCC values and the possible dilution effect of CaO on other major oxides. Environmental risk assessment indices (Igeo and EF) reveal that the lake surface sediments are low to moderately enriched with Cu, Ni, Zn and Pb and thus are a direct threat to aquatic life. Pollution load index indicates higher contamination of the sediment samples collected along the agricultural and urban land-cover sites. In the absence of industries and metal mines in the catchment area, the agricultural inputs, domestic effluents and untreated sewage discharges are the probable source for the moderate increase in trace metals in the lake sediments. Based on geochemical and environmental parameters, an assessment of sediment contamination results revealed potential risks ranging from moderate to strong for the lake environment, particularly towards areas proximal to agricultural and land-use sites. The above results from this study thus add to the fundamental knowledge of the present lake processes occurring within the lake and its interactions with the surrounding catchment areas.

Geochemistry, spatial distribution and environmental risk assessment of the surface sediments: Anchar Lake, Kashmir Valley, India

Controls on the isotopic composition of daily precipitation characterized by dual moisture transport pathways at the monsoonal margin region of North-Western India

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

In this review, the shifts in organic matter (OM) accumulation and C:N ratios in lake sediments to reconstruct paleoclimate and paleo-environmental changes since the early Holocene period are presented. The C:N proxy data of total OM reflect wet climatic conditions during early Holocene (10 to 8.2 kyrs BP) due to enhanced southwest monsoon. This was followed by intermittent arid conditions during the mid and late Holocene period (8.2 to 2.8 kyr BP). Enhanced values of C:N ratio during middle to late Holocene (7.8–2.3 kyrs B.P) indicate periods with lower lake levels and minimum precipitation, while decreased C:N ratio point to stronger SW monsoon and expansion of the lakes. Further, C:N and δ13C results from the lake sediments reveal a detailed and continuous paleo-environmental changes in the relative sources of OM (allochthonous vs autochthonous). Proxy records using such natural archives have also been utilized to reconstruct past extreme events and environmental changes around the lake systems, such as causes for lake desiccation, hydrographic changes, alternations between C3 and C4 vegetation and historical disturbances in the catchment area since the early-late Holocene period coupled with the Indian summer monsoon.

Reconstruction of Paleoclimate and Environmental Fluctuations Since the Early Holocene Period Using Organic Matter and C:N Proxy Records: A Review

Small islands in the Arabian Sea such as the Lakshadweep Islands offer a unique ecosystem that harbours diverse types of flora and fauna. Cyclone Ockhi which occurred on 1 December 2017 caused severe damage to the ecosystem and economy, particularly in Minicoy Island, Lakshadweep. Here we provide an overview of the after effects of the cyclone. Initially, a low pressure area formed over the Andaman Sea on 22 November 2017, under the influence of a remnant upper air cyclonic circulation from the Gulf of Thailand. Subsequently, it developed over the southern part of the Bay of Bengal and moved westwards causing rainfall activity over southern peninsular India at regular intervals. After landfall, it crossed Tamil Nadu and Kerala, and then headed towards the Minicoy Island. Figure 1 shows the storm track. Cyclone Ockhi was categorized as a Very Severe Cyclonic Storm that achieved a peak intensity of 150–160 kmph and lowest central pressure of 976 hPa (https://earth. nullschool.net/) on 1 December 2017, causing a widespread damage to the island infrastructure and its agriculture system (Figure 2). Though no human casualty was reported, a large number of animals, both domestic and marine, were killed and coral reefs destroyed. Table 1 presents the total estimated loss and damage incurred due to cyclone. Strong winds damaged houses, especially those located along the shoreline and towards the western side of the Island, where there is a dense growth of coconut and other plants. Public infrastructure, including high-level mobile towers and schools sustained heavy damage. The storm surge and strong winds resulted in the destruction of property and the natural environment, including a variety of corals. Marine shells, including

A. A. Fousiya

Papers

Geochemistry, spatial distribution and environmental risk assessment of the surface sediments: Anchar Lake, Kashmir Valley, India

Controls on the isotopic composition of daily precipitation characterized by dual moisture transport pathways at the monsoonal margin region of North-Western India

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

Reconstruction of Paleoclimate and Environmental Fluctuations Since the Early Holocene Period Using Organic Matter and C:N Proxy Records: A Review

Cyclone Ockhi and its Impact Over Minicoy Island, Lakshadweep, India