T2.1 Drivers of O2/OHC trends in a water-mass framework
We will use the unique bonding of O2- and OHC-trends to evaluate the reasons for the underestimation of O2 trends in the historical simulation of selected fully coupled CMIP6 ESMs and its implication for projected O2 trends under a high CO2-future (SSP5-8.5). We will use a water mass framework to assess modelled OHC and O2-trends, and to divide O2-trends into solubility- and respiration/circulation-driven changes and compare this to the estimates of T1.1, identifying the reason for model error. We will also quantify if a high resolution global climate model (GCM) allows for a more realistic water mass and OHC-representation and use the OHC-output of the GCM to infer O2 changes from given O2/OHC-ratios in observations.
T2.2 High latitude North Atlantic circulation changes and its impact on O2
We will analyze the impact of advective pathways of the high latitude North Atlantic on the upper ocean O2 distribution in the historical and SSP5-8.5 scenario in a CMIP6 model ensemble. Here, we will first assess the impact of changes in circulation and vertical mixing on the distributions of nutrients and its biology-induced impact on upper-ocean O2 based on a simple frameworkWH20. Subsequently, we analyze surface temperature changes along these advective pathways and their impact on O2 solubility.
T2.3 Impacts of northward heat transports on Nordic Seas OHC and O2
Building on Madonna and SandøMA21, we will analyze ocean heat transport (OHT), mixed layer depth/density and OHC from selected CMIP6-output from the historical simulation. We will regress the modelled OHT on mixed layer density/depth, O2 and OHC. Through data-comparison, we will find the most realistic model and, based on the regression analysis and discuss distributions of O2 and OHC with respect to northward OHT.