Water isotopes in the ocean trace the freshwater exchanges between the ocean, the atmosphere and the cryosphere, and are used to investigate processes of the hydrological cycle. We illustrate offsets in seawater isotopic composition between different data sets that are larger than the expected variability that one often wants to explore. This highlights the need to share seawater isotopic composition samples dedicated to specific intercomparison of data produced in the different laboratories.

The extent of mankind’s influence on Earth’s climate warrants ocean-studies. A supposed major heat-transporter is the Atlantic Meridional Overturning Circulation (AMOC). As AMOC is a complex nonlinear dynamical system, mathematical models may predict its potential collapse using single parameters like surface temperature. However, physical processes such as (sub-)mesoscale eddy transport and turbulent mixing by internal wave breaking will alter the estimators, so that the AMOC may not collapse.