A global 1/4° ocean/sea ice 50‐member ensemble simulation is used to disentangle the low‐frequency imprints of the atmospherically forced oceanic variability and of the chaotic intrinsic oceanic variability (IOV) on the large‐scale (10° × 10°) ocean heat content (OHC) between 1980 and 2010. The IOV explains most of the interannual‐to‐decadal large‐scale OHC variance over substantial fractions of the global ocean area that increase with depth: 9%, 22%, and 31% in the 0–700 m, 700–2000 m and 2000 m bottom layers, respectively. Such areas concern principally eddy‐active regions, mostly found in the Southern Ocean and in western boundary current extensions, and also concern the subtropical gyres at intermediate and deep levels. The oceanic chaos may also induce random multidecadal fluctuations so that large‐scale regional OHC trends computed on the 1980–2010 period cannot be unambiguously attributed to the atmospheric forcing in several oceanic basins at various depths. These results are likely to raise detection and attribution issues from real observations.

A global ¼° ocean/sea‐ice 50‐member ensemble simulation is analyzed to disentangle the imprints of the atmospheric forcing and the chaotic ocean variability on regional sea level trends over the satellite altimetry period. We find that the chaotic ocean variability may mask atmospherically forced regional sea level trends over 38% of the global ocean area from 1993 to 2015, and over 47% of this area from 2005 to 2015. These regions are located in the western boundary currents, in the Southern Ocean and in the subtropical gyres. While these results do not question the anthropogenic origin of global mean sea level rise, they give new insights into the intrinsically oceanic versus atmospheric forcing of regional sea level trends and provide new constraints on the measurement time required to attribute regional sea level trends to the atmospheric forcing or to climate change.

Global mean sea level has experienced an unabated rise over the 20^th century. This observed rise is due to both ocean warming and increasing continental freshwater discharge. We estimate the net ocean mass contribution to sea level by assessing the global ocean salt budget based on the unprecedented amount of in situ data over 2005–2015. We obtain the ocean mass trends of 1.30 ± 1.13 mm · yr⁻¹ (0–2000 m) and 1.55 ± 1.20 mm · yr⁻¹ (full depth). These new ocean mass trends are smaller by 0.63–0.88 mm · yr⁻¹ compared to the ocean mass trend estimated through the sea level budget approach. Our result provides an independent validation of Gravity Recovery And Climate Experiment (GRACE)-based ocean mass trend and, in addition, places an independent constraint on the combined Glacial Isostatic Adjustment – the Earth’s delayed viscoelastic response to the redistribution of mass that accompanied the last deglaciation- and geocenter variations needed to directly infer the ocean mass trend based on GRACE data.

Global mean sea level rose by 15 mm over June 2014 – May 2016. This rise is 7 mm larger than the 8 mm increase associated with the long‐term trend of 4 mm/yr estimated over 2006–2016. Using a combination of satellite gravimetry data and in situ measurements, we find that 20% of this rise is explained by ocean thermal expansion and 80% by an ocean mass increase, the latter being largely correlated with an equivalent terrestrial water storage (TWS) decrease. Half of the global ocean mass increase during that period can be attributed to the South American continent where we find a significant contribution of the TWS over the Amazon basin (5 mm). This TWS change between oceans and continents occurred during two El Nino events: one aborted in 2014–2015 and an extreme event in 2015–2016 which affected precipitation patterns, especially over the equatorial Pacific ocean and over South America.