By reconstructing the history of water impoundment in the world's artificial reservoirs, we show that a total of approximately 10,800 cubic kilometers of water has been impounded on land to date, reducing the magnitude of global sea level (GSL) rise by -30.0 millimeters, at an average rate of -0.55 millimeters per year during the past half century. This demands a considerably larger contribution to GSL rise from other (natural and anthropogenic) causes than otherwise required. The reconstructed GSL history, accounting for the impact of reservoirs by adding back the impounded water volume, shows an essentially constant rate of rise at +2.46 millimeters per year over at least the past 80 years. This value is contrary to the conventional view of apparently variable GSL rise, which is based on face values of observation.

[1] Recent studies suggest the increasing contribution of groundwater depletion to global sea-level rise. Groundwater depletion has more than doubled during the last decades, primarily due to increase in water demand, while the increase in water impoundments behind dams has been tapering off since the 1990s. As a result, the contribution of groundwater depletion to sea-level rise is likely to dominate over those of other terrestrial water sources in the coming decades. Yet, no projections into the 21st century are available. Here we present a reconstruction of past groundwater depletion and its contribution to global sea-level variation, as well as 21st century projections based on three combined socio-economic and climate scenarios (SRES) with transient climate forcing from three General Circulation Models (GCMs). We validate and correct estimated groundwater depletion with independent local and regional assessments, and place our results in context of other terrestrial water contributions to sea-level variation. Our results show that the contribution of groundwater depletion to sea-level increased from 0.035 (AE0.009) mm yr À1 in 1900 to 0.57 (AE0.09) mm yr À1in 2000, and is projected to increase to 0.82 (AE0.13) mm yr À1 by the year 2050. We estimate the net contribution of terrestrial sources to be negative of order À0.15 (AE0.09) mm yr À1 over 1970-1990 as a result of dam impoundment. However, we estimate this to become positive of order +0.25 (AE0.09) mm yr À1 over 1990-2000 due to increased groundwater depletion and decreased dam building. We project the net terrestrial contribution to increase to +0.87 (AE0.14) mm yr À1 by 2050. As a result, the cumulative contribution will become positive by 2015, offsetting dam impoundment (maximum À31 AE 3.1 mm in 2010), and resulting in a total rise of +31 (AE11) mm by 2050. Citation: Wada, Y., L.

We study the impact of phase noise on the downlink performance of a multi-user multiple-input multiple-output system, where the base station (BS) employs a large number of transmit antennas M . We consider a setup where the BS employs Mosc free-running oscillators, and M/Mosc antennas are connected to each oscillator. For this configuration, we analyze the impact of phase noise on the performance of regularized zero-forcing (RZF) precoding, when M and the number of users K are asymptotically large, while the ratio M/K = β is fixed. We analytically show that the impact of phase noise on the signal-to-interference-plusnoise ratio (SINR) can be quantified as an effective reduction in the quality of the channel state information available at the BS when compared to a system without phase noise. As a consequence, we observe that as Mosc increases, the SINR of the RZF precoder degrades as the interference power increases, and the desired signal power decreases. On the other hand, the variance of the random phase variations caused by the BS oscillators reduces with increasing Mosc. Through simulations, we verify our analytical results, and study the performance of the RZF precoder for different phase noise and channel noise variances.

No abstract

CS-NMR improves the temporal resolution of conventional multi-dimensional NMR for species identification and study of reaction kinetics.