Approximately 10 million m3 x s(-1) of water flow from the Pacific Ocean into the Indian Ocean through the Indonesian seas. Within the Makassar Strait, the primary pathway of the flow, the Indonesian throughflow is far cooler than estimated earlier, as pointed out recently on the basis of ocean current and temperature measurements. Here we analyse ocean current and stratification data along with satellite-derived wind measurements, and find that during the boreal winter monsoon, the wind drives buoyant, low-salinity Java Sea surface water into the southern Makassar Strait, creating a northward pressure gradient in the surface layer of the strait. This surface layer 'freshwater plug' inhibits the warm surface water from the Pacific Ocean from flowing southward into the Indian Ocean, leading to a cooler Indian Ocean sea surface, which in turn may weaken the Asian monsoon. The summer wind reversal eliminates the obstructing pressure gradient, by transferring more-saline Banda Sea surface water into the southern Makassar Strait. The coupling of the southeast Asian freshwater budget to the Pacific and Indian Ocean surface temperatures by the proposed mechanism may represent an important negative feedback within the climate system.

Six water emergencies have occurred since 1981 for the New York City (NYC) region despite the following: 1) its perhumid climate, 2) substantial conservation of water since 1979, and 3) meteorological data showing little severe or extreme drought since 1970. This study reconstructs 472 years of moisture availability for the NYC watershed to place these emergencies in long-term hydroclimatic context. Using nested reconstruction techniques, 32 tree-ring chronologies comprised of 12 species account for up to 66.2% of the average MayAugust Palmer drought severity index. Verification statistics indicate good statistical skill from 1531 to 2003. The use of multiple tree species, including rarely used species that can sometimes occur on mesic sites like Liriodendron tulipifera, Betula lenta, and Carya spp., seems to aid reconstruction skill. Importantly, the reconstruction captures pluvial events in the instrumental record nearly as well as drought events and is significantly correlated to precipitation over much of the northeastern United States. While the mid-1960s drought is a severe drought in the context of the new reconstruction, the region experienced repeated droughts of similar intensity, but greater duration during the sixteenth and seventeenth centuries. The full record reveals a trend toward more pluvial conditions since ca. 1800 that is accentuated by an unprecedented 43-yr pluvial event that continues through 2011. In the context of the current pluvial, decreasing water usage, but increasing extra-urban pressures, it appears that the water supply system for the greater NYC region could be severely stressed if the current water boom shifts toward hydroclimatic regimes like the sixteenth and seventeenth centuries.

The Indonesian Throughflow (ITF) is considered central to the heat budgets of the Pacific and Indian Oceans. Temperature and ocean current time series obtained within the Makassar Strait from December 1996 to early July 1998 are used to calculate heat transport of the ITF and assess its influence on Indian Ocean heat divergence. Velocity and temperature values for the surface layer that were not directly measured are extrapolated from the shallowest measurement to the sea surface using a variety of model profiles. While a single temperature profile is used based on a linear interpolation from NCEP OI sea-surface temperatures to the top-most mooring temperature recorder, four different velocity profiles are employed. Heat transport is calculated as volume transport multiplied by temperature, density and specific heat, using reference temperatures between 01C and 41C. The mean heat transport averages 0.55 PW relative to 01C, and 0.41 PW relative to 41C for the two most reasonable velocity profiles. In comparison, model heat transport values are larger, between 0.6 and 1.15 PW. Heat transport varies with ENSO phase, lower during El Ni * no, higher during La Ni * na. As 1997 was a strong El Ni * no year, our heat transport estimate may be less than the climatic mean. The ITF water is advected towards Africa within the Indian Ocean South Equatorial Current, to eventually exit the Indian Ocean across 301S, most likely within the Agulhas Current. For realistic consideration of the ITF component within the Agulhas Current, the heat flux divergence of ITF waters within the Indian Ocean north of 301S is found to be insignificant. Our results provide support for model studies and hydrographic geostrophic inverse calculations that indicate the ITF heat, derived from the Pacific Ocean, is ultimately lost to the atmosphere in the southwest Indian Ocean. r