A global Finite-Element Sea-Ice ocean model focussed on deep water formation areas: Variability of North Atlantic deep water formation and interannual to decadal climate modes

• Main Author: Scholz, Patrick
• Other Authors: Lohmann, Gerrit, Rhein, Monika
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2012
• Subjects: finite elements; ocean model; climate modes; Labrador Sea Water; evaluation; 570; 570 Life sciences; biology; ddc:570; Greenland; Ross Sea; Weddell; Weddell Sea; Greenland Sea; Labrador Sea; Nordic Sea; North Atlantic Deep Water; North Atlantic; Sea ice
• Online Access: https://media.suub.uni-bremen.de/handle/elib/384; https://nbn-resolving.org/urn:nbn:de:gbv:46-00102793-13

This study aims to validate the ability of the Finite-Element Sea-Ice Ocean Model (FESOM) to reproduce a reliable deep water formation in North Atlantic ocean and to analyse its variability on interannual to decadal time-scales. The FESOM approach works on unstructured triangular surface meshes, which allows us to faithfully resolve coastlines and local areas of interest. The first part of the thesis presents the characteristics of a global FESOM setup designed to study the variability in the deep-water formation areas over five decades for the period 1958-2004. The setup features a regionally increased resolution in the deep water formation areas in the Labrador Sea, Greenland Sea, Weddell Sea and Ross Sea as well as in equatorial and coastal areas. Further, this part of the thesis deals with the applied spinup procedure and the general validation of the FESOM model setup with respect to the performance of the sea-ice and ocean model component. Based on the analysis of the Atlantic Meridional Overturning Circulation (AMOC) we demonstrate that the upper ocean is converged within the applied spinup procedure. The sea ice model reproduces realistic sea-ice distributions and variabilities in the sea ice extent on both hemispheres as well as sea ice transport that compares well with observational data. The general ocean circulation model is validated based on a comparison of the model results with Ocean Weather Ship data in the North Atlantic. We can prove that the vertical structure is well captured in areas with improved resolution. Further, we are able to simulate the decadal ocean variability in the Nordic Sea Overflows as well as several salinity anomaly events and corresponding fingerprint in the vertical hydrography. The second part of the thesis focuses on the validation of the model capability to reproduce a realistic deep-water formation in the Labrador Sea. Therefor, we examine two classes of Labrador Sea water (LSW) which are analysed and compared to observed LSW layer thicknesses derived from profile ...