Long-Term Ventilation Changes in North Atlantic Mode and Labrador Sea Waters: Insights from Formation Rate and Oxygen Observations Over Six Decades

Montag 06.05.2024, 11:00 → 12:00 Europe/Berlin

8A-002 - Hörsaal Ostufer / Lecture Hall East (GEOMAR - Standort Ostufer / GEOMAR - East Shore)

Speaker: Ilaria Stendardo, Universität Bremen

Hybrid  - Zoom: https://geomar-de.zoom.us/j/84289388604?pwd=dGlpeTBUd1Nxem5Ec3dRYXh4NFpOUT09

Abstract        
Subpolar Mode Water (SPMW) and Labrador Sea Water (LSW) are vital components of the North Atlantic’s Ocean circulation system. This study investigates long-term ventilation changes in these water masses, integrating insights from formation rate analysis based on two complementary approaches and oxygen observations over six decades. Utilizing observational datasets spanning from 1993 to 2018, we examined the formation rates and temporal variability of SPMW using two complementary approaches: a thermodynamic approach focusing on the air-sea interactions and a kinematic approach involving volume transport from the mixed layer to the ocean’s interior, including the entrainment/detrainment of the mixed layer itself. Additionally, we analyzed dissolved oxygen concentrations spanning from 1960 to 2022, apparent oxygen utilization (AOU), oxygen utilization rate (OUR), and water mass ages within the upper 2000 meters of the water column, focusing on SPMW, Intermediate Water (IW), and LSW. Tracer-based ventilation analysis, employing chlorofluorocarbons (CFCs) and Sulphur hexafluoride (SF6) data, is also performed in order to provide insights into ventilation ages and the relative contributions of air-sea gas exchanges, ocean circulation, and marine biology to oxygen variability. Our findings underscore the complex dynamics governing long-term ventilation changes in the North Atlantic Mode and Labrador Sea Waters, highlighting their significance in understanding global ocean circulation and climate.