Changes in the climate system's energy budget are predominantly revealed in ocean temperatures and the associated thermal expansion contribution to sea-level rise. Climate models, however, do not reproduce the large decadal variability in globally averaged ocean heat content inferred from the sparse observational database, even when volcanic and other variable climate forcings are included. The sum of the observed contributions has also not adequately explained the overall multi-decadal rise. Here we report improved estimates of near-global ocean heat content and thermal expansion for the upper 300 m and 700 m of the ocean for 1950-2003, using statistical techniques that allow for sparse data coverage and applying recent corrections to reduce systematic biases in the most common ocean temperature observations. Our ocean warming and thermal expansion trends for 1961-2003 are about 50 per cent larger than earlier estimates but about 40 per cent smaller for 1993-2003, which is consistent with the recognition that previously estimated rates for the 1990s had a positive bias as a result of instrumental errors. On average, the decadal variability of the climate models with volcanic forcing now agrees approximately with the observations, but the modelled multi-decadal trends are smaller than observed. We add our observational estimate of upper-ocean thermal expansion to other contributions to sea-level rise and find that the sum of contributions from 1961 to 2003 is about 1.5 +/- 0.4 mm yr(-1), in good agreement with our updated estimate of near-global mean sea-level rise (using techniques established in earlier studies) of 1.6 +/- 0.2 mm yr(-1).

humidity, we expect a 7% increase in atmospheric moisture content for every degree of 30 warming of the Earth's lower troposphere (2). Of greatest importance to society, and the focus 31 of this work, is the strength of the regional pattern of evaporation and precipitation (E--P), 32 which in climate models scales approximately with CC, while global precipitation changes more 33 slowly at a rate of 2--3% °C --1 (2, 4). 34An intensification of existing patterns of global mean surface evaporation and precipitation (E-- do not yet have a definitive view on whether the Earth's water cycle has intensified over the 61 past several decades from atmospheric observing networks (12,20). 62It has long been noted that the climatological mean sea surface salinity (SSS) spatial pattern is 63 highly correlated with the long--term mean E--P spatial pattern (21) ( estimates of long--term SSS change (24, 25, 27). Following the "rich get richer" mechanism (7) Table S2). Our examples of the simulations 117 that most closely replicate the observed spatial change and mean patterns (Fig. 1E, H) and 118 those that produce an almost inverse spatial change pattern (Fig. 1F, I) compared to the 119 observed results (Fig. 1D, G), illustrate the range of responses found in CMIP3 (Fig. 1). Some 120 models show similar numbers to those observed (Fig. 1E, H The PA and PC methodology can also be used when considering other variables, such as the 126 surface water flux (E--P). CMIP3 simulations show a relationship between SSS PA and the E--P PA 127 (Fig. 2B). This key result supports the use of SSS PA as a diagnostic of a changing water cycle, 128 and also provides a relationship in which to consider the observed SSS PA for 1950--2000. The 129CMIP3 SSS patterns amplify at twice the rate of E--P patterns (Fig. 2B) Figure S9). 136For both the 20C3M and SRES CMIP3 simulations, we find a clear relationship between the rate 137 of global average surface warming (ΔTa) and the rate of SSS PA and PC strength ( Fig. 2A). 13820C3M simulations in which the warming rate is low (generally those with comprehensive 139 aerosol schemes; contrast diamonds and circles in Fig. S5; Table S1) suggests that SSS patterns intensify with warming at 8% °C --1 ( Fig. 2A), which is half of our 1950--147 2000 observed rate (16% °C --1 ; Fig. 2A). As expected, based on past analyses of CMIP3 (2), the E--148 P PA is also linearly related to surface warming rates (Fig. 2C) surface water flux, near 3.1% °C --1 (Fig. 2D). The stronger SSS PA response to warming and 152 tighter agreement among CMIP3 when compared to that for the E--P PA ( Fig. 2A vs C To independently demonstrate the strong relationship between 50--year salinity change and an 159 enhanced water cycle, the response of an ocean--only model to an idealised 5% E--P pattern 160 increase was explored. We used a version of the MOM3 ocean model, forced with E--P fields 161 obtained from the NCEP reanalysis. A linear trend in E--P was imposed to achieve a 5% increase (which shows that SSS PA increases at twice the rat...

[1] The mean and variable transport of the Indonesian Throughflow (ITF) are determined from full-depth velocity measurements in the three major exit passages of Lombok Strait, Ombai Strait, and Timor Passage from January 2003 through December 2006. Collectively, these passages convey the full-depth transport and stratification profile of the ITF from the Pacific Ocean to the Indian Ocean. To first order, the seasonal cycle of transport in the thermocline ($100-150 m) in all three exit straits is dominated by regional monsoon forcing, with maximum ITF during the southeast monsoon. During the northwest monsoon, the surface transport relaxes in Timor and weakly reverses in Ombai and Lombok, so the main core of the ITF is subsurface. Below the thermocline, semiannual reversals occur in all three straits during the monsoon transitions in response to the passage of Indian Ocean wind-forced Kelvin waves. However, the reversals occur over different depth levels in each passage reflecting the influence of different sill depths along the coastal waveguide. The seasonal cycle of depth-integrated transports in Lombok and Ombai are strongly out of phase with Timor Passage, suggesting that the subthermocline flow is largely gated by these Kelvin waves. Despite the different seasonal transport phases, interannual anomalies in all three passages are remarkably similar, particularly during the strong positive Indian Ocean Dipole event in 2006 when transport in the surface layer is toward the Indian Ocean and reversed below. The deep reversals are likely in response to a series of Kelvin waves driven by anomalous zonal winds in the equatorial Indian Ocean. Total mean transport over the 3-year period is À2.6 Sv in Lombok Strait (i.e., toward the Indian Ocean), À4.9 Sv in Ombai Strait, and À7.5 Sv in Timor Passage. The transport in Timor Passage is nearly twice as large as historical estimates and represents half of the À15 Sv full-depth ITF transport that enters the Indian Ocean.

Using over 1.6 million profiles of salinity, potential temperature, and neutral density from historical archives and the international Argo Program, this study develops the three-dimensional field of multidecadal linear change for ocean-state properties. The period of analysis extends from 1950 to 2008, taking care to minimize the aliasing associated with the seasonal and major global El Niñ o-Southern Oscillation modes. Large, robust, and spatially coherent multidecadal linear trends in salinity to 2000-dbar depth are found. Salinity increases at the sea surface are found in evaporation-dominated regions and freshening in precipitationdominated regions, with the spatial pattern of change strongly resembling that of the mean salinity field, consistent with an amplification of the global hydrological cycle. Subsurface salinity changes on pressure surfaces are attributable to both isopycnal heave and real water-mass modification of the temperaturesalinity relationship. Subduction and circulation by the ocean's mean flow of surface salinity and temperature anomalies appear to account for most regional subsurface salinity changes on isopycnals. Broad-scale surface warming and the associated poleward migration of isopycnal outcrops drive a clear and repeating pattern of subsurface isopycnal salinity change in each independent ocean basin. Qualitatively, the observed global multidecadal salinity changes are thus consonant with both broad-scale surface warming and the amplification of the global hydrological cycle.

Increasing heat content of the global ocean dominates the energy imbalance in the climate system 1 . Here we show that ocean heat gain over the 0-2,000 m layer continued at a rate of 0.4-0.6 W m −2 during 2006-2013. The depth dependence and spatial structure of temperature changes are described on the basis of the Argo Program's 2 accurate and spatially homogeneous data set, through comparison of three Argo-only analyses. Heat gain was divided equally between upper ocean, 0-500 m and 500-2,000 m components. Surface temperature and upper 100 m heat content tracked interannual El Niño/Southern Oscillation fluctuations 3 , but were o set by opposing variability from 100-500 m. The net 0-500 m global average temperature warmed by 0.005 • C yr −1 . Between 500 and 2,000 m steadier warming averaged 0.002 • C yr −1 with a broad intermediate-depth maximum between 700 and 1,400 m. Most of the heat gain (67 to 98%) occurred in the Southern Hemisphere extratropical ocean. Although this hemispheric asymmetry is consistent with inhomogeneity of radiative forcing 4 and the greater area of the Southern Hemisphere ocean, ocean dynamics also influence regional patterns of heat gain.Global ocean sampling of water-column temperature in the twentieth century was spatially and temporally sparse 5 , characterized by strong coverage biases towards the Northern Hemisphere, towards the continental coastlines, and seasonally towards summer. Roughly half a million temperature/salinity profiles to at least 1,000 m were collected by research vessels, mostly in the past 50 years. Additional lower accuracy and shallower temperature-only data have been obtained from commercial and naval vessels. These help to mitigate the coverage deficiencies but raise additional concerns regarding measurement bias errors 6 .Today the Argo Program 2 provides systematic coverage of global ocean temperature/salinity from 0-2,000 m using 3,500 autonomous profiling floats spaced about every 3 • of latitude and longitude, each providing a temperature/salinity profile every 10 days. Profiling float technology 7 allows data to be collected without a ship by long-lived free-drifting instruments. Argo has collected 1.2 million temperature/salinity profiles and continues to provide 10,000 profiles per month, with far greater spatial and temporal homogeneity than that achieved historically. Previous investigations of ocean heat content 5 have combined Argo and historical data of variable quality, and these studies have been impacted by coverage and measurement bias issues. Here we estimate ocean heat gain over the 2006-2013 period for which Argo coverage is global (Methods), and through the exclusive use of Argo data with uniformly high quality.Argo's ocean temperature data set is invaluable for estimating the net radiation balance of the Earth. The deduced excess of downward over outgoing radiation 8 driving global warming is too small to measure directly as radiative fluxes 9 . About 93% of this net planetary energy increase is stored in the oceans 1 , a result of the ...

In recent years, autonomous profiling floats have become the prime component of the in situ ocean observing system through the implementation of the Argo program. These data are now the dominant input to estimates of the evolution of the global ocean heat content and associated thermosteric sea level rise. The Autonomous Profiling Explorer (APEX) is the dominant type of Argo float (;62%), and a large portion of these floats report pressure measurements that are uncorrected for sensor drift, the size and source of which are described herein. The remaining Argo float types are designed to automatically self-correct for any pressure drift. Only about 57% of the APEX float profiles (or ;38% Argo profiles) can be corrected, but this typically has not been done by the data centers that distribute the data (as of January 2009). A pressure correction method for APEX floats is described and applied to the Argo dataset. A comparison between estimates using the corrected Argo dataset and the publically available uncorrected dataset (as of January 2009) reveals that the pressure corrections remove significant regional errors from ocean temperature, salinity, and thermosteric sea level fields. In the global mean, 43% of uncorrectable APEX float profiles (or ;28% Argo profiles) appear to largely offset the effect of the correctable APEX float profiles with positive pressure drifts. While about half of the uncorrectable APEX profiles can, in principle, be recovered in the near future (after inclusion of technical information that allows for corrections), the other half have negative pressure drifts truncated to zero (resulting from firmware limitations), which do not allow for corrections. Therefore, any Argo pressure profile that cannot be corrected for biases should be excluded from global change research. This study underscores the ongoing need for careful analyses to detect and remove subtle but systematic errors in ocean observations.

More than 90% of the heat energy accumulation in the climate system between 1971 and the present has been in the ocean. Thus, the ocean plays a crucial role in determining the climate of the planet. Observing the oceans is problematic even under the most favourable of conditions. Historically, shipboard ocean sampling has left vast expanses, particularly in the Southern Ocean, unobserved for long periods of time. Within the past 15 years, with the advent of the global Argo array of pro ling oats, it has become possible to sample the upper 2,000 m of the ocean globally and uniformly in space and time. The primary goal of Argo is to create a systematic global network of pro ling oats that can be integrated with other elements of the Global Ocean Observing System. The network provides freely available temperature and salinity data from the upper 2,000 m of the ocean with global coverage. The data are available within 24 hours of collection for use in a broad range of applications that focus on examining climate-relevant variability on seasonal to decadal timescales, multidecadal climate change, improved initialization of coupled ocean-atmosphere climate models and constraining ocean analysis and forecasting systems.

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