Research Highlights

In a recent technical comment, Zhang et al. show that ocean dynamics play a central role in the Atlantic Multidecadal Oscillation (AMO), and the previous claims that “the AMO is a thermodynamic response of the ocean mixed layer to stochastic atmospheric forcing, and ocean circulation changes have no role in causing the AMO” are not justified.

Ocean-to-land moisture transport leaves an imprint on sea surface salinity, making this “nature’s rain gauge” to measure the variations of the water cycle. Two new studies provide strong evidence that salinity in the subtropical North Atlantic is a skillful predictor for precipitation in the African Sahel and the US Midwest.

There is very little doubt that human-driven climate warming will ultimately result in widespread ocean deoxygenation; however, substantial natural variation and sparse observational records make it difficult to determine when. New research suggests that human-driven changes in oxygen levels are evident in many oceanic regions now and will be widespread in the next 15-20 years.

New research shows how easterly winds in the summer of 2014 caused the anomalously warm subsurface water of the tropical Pacific—which presages an El Niño event and formed following the early 2014 westerly wind burst—to never discharge poleward, thereby remaining in the tropical Pacific and giving a head start to the developing 2015-16 El Niño.

Many people were counting on the strong El Niño this winter to produce surplus water to recharge the groundwater and make up for what’s been pumped out due to the severe drought. However, a new study found that the groundwater level in California’s Central Valley has continued to decline even when drought has recovered.