The Bay of Bengal receives a large influx of freshwater from precipitation and river discharge. Outflow of excess freshwater and inflow of saltier water is required to prevent the bay from freshening. Relatively fresh water flows out of the bay along its boundaries and inflow of saltier water occurs via the Summer Monsoon Current (SMC), which flows eastward from the Arabian Sea into the bay. This saltier water, however, slides under the lighter surface water of the bay. Maintaining the salt balance of the bay therefore demands upward mixing of this saltier, subsurface water. Here, we show that an efficient mechanism for this mixing is provided by upward pumping of saltier water in several bursts during the summer monsoon along the meandering path of the SMC. Advection by currents can then take this saltier water into the rest of the basin, allowing the bay to stay salty despite a large net freshwater input.

We present here a 11,000-year palaeomonsoonal record from a sediment core (SS-1) from Shantisagara (SS) Lake in Peninsular India, which is the longest published so far from the region. This is also a region with limited palaeoclimate records. Environmental magnetic, organic geochemical, sedimentological and carbon isotopic studies were carried out on the SS-1 sediments to reconstruct the Indian summer monsoon (ISM) variability during the Holocene. The chronology of the sediments is constrained by three AMS 14 C dates. Environmental magnetic data reveal that there is no contribution from bacterial magnetite, greigite and anthropogenic magnetite/lithogenic grains and that the magnetic signal is contributed mainly by the pedogenic component. The environmental magnetic data also depict variations in pedogenic magnetite production in the catchment and detrital influx to the lake, which in turn is related to monsoonal rainfall amount. The sedimentological data reveal variations in sediment size related to monsoon. The C org /N ratio and δ 13 C indicate palaeovegetational variations in the SS catchment. Periods of strong monsoon are characterised by high values of concentration-dependent magnetic parameters like χ lf , χ fd , χ ARM and SIRM, high sand content, low C org /N ratio (fully aquatic-deep water conditions), relatively depleted δ 13 C values (more C 3 but less C 4 land plants) and vice versa. The prominent palaeomonsoon events documented in this study are: (i) 11,100-10,700 cal yr BP with a weak ISM, (ii) 10,700 to 8600 cal yr BP characterized by intensified ISM, corresponding to the Early Holocene Optimum, (iii) 8600 to 4500 cal yr BP with a weakened ISM (iv) 4500 to 3300 cal yr BP characterized by fluctuating monsoonal conditions, (v) 3300 cal yr BP to the Present with a slight increasing trend in ISM. A similar pattern is also documented in many palaeomonsoon records from the region, which indicate that Shantisagara sediments were able to record regional climatic variations as well.

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ABSTRACT. Groundwater is a common-pool resource that is subject to depletion in many places around the world as a result of increased use of irrigation and water-demanding cash crops. Where state capacity to control groundwater use is limited, collective action is important to increase recharge and restrict highly water-consumptive crops. We present results of field experiments in hard rock areas of Andhra Pradesh, India, to examine factors affecting groundwater use. Two nongovernmental organizations (NGOs) ran the games in communities where they were working to improve watershed and water management. Results indicate that, when the links between crop choice and groundwater depletion is made explicit, farmers can act cooperatively to address this problem. Longer NGO involvement in the villages was associated with more cooperative outcomes in the games. Individuals with more education and higher perceived community social capital played more cooperatively, but neither gender nor method of payment had a significantly effect on individual behavior. When participants could repeat the game with communication, similar crop choice patterns were observed. The games provided an entry point for discussion on the understanding of communities of the interconnectedness of groundwater use and crop choice.

Understanding the factors that control the variability of oxygen isotopic ratios (δ18O) of Indian Summer Monsoon (ISM) rainfall (δ18Op) is of vital importance for the interpretation of δ18Op derived from climate proxies (e.g., speleothem and tree ring cellulose) of this region. Here we demonstrate the importance of moisture transport pathways on spatiotemporal variations of ISM δ18Op using a new set of daily observations from central and northern India and previously reported data aided by simulations from an isotope‐enabled General Circulation Model. 18O‐depleted rain events are characterized by a higher number of air parcel back trajectories through the Bay of Bengal branch of moisture transport, while those through the Arabian Sea branch are associated with 18O enriched rain events. This effect is observed on intraseasonal to interannual timescales in the long‐term observations at New Delhi as well. Thus, the shift in moisture transport regimes must be considered when interpreting δ 18Op from climate proxies of the ISM region.