EGU23-8176
https://doi.org/10.5194/egusphere-egu23-8176
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Weddell Gyre: what drives a long-term increase in surface nutrients?

Krissy Anne Reeve1, Mario Hoppema1, Torsten Kanzow1,2, Olaf Boebel1, Walter Geibert1, and Volker Strass1
Krissy Anne Reeve et al.
  • 1Alfred Wegener Institute, Physical Oceanography of the Polar Seas, Bremerhaven, Germany (kreeve@awi.de)
  • 2Bremen University, Department of Physics and Electrical Engineering Bremen, Germany

The Weddell Gyre plays a role in connecting the deep ocean to the surface through upwelling, and also in feeding heat towards the Antarctic ice shelves, regulating the density of water masses that feed the deepest limb of the global overturning circulation. Using Argo floats freely drifting throughout the Weddell Gyre, we describe its horizontal circulation as an elongated double-gyre system, with stronger transports in the east than in west, impacting water property distribution. The eastern sub-gyre region is also associated with stronger upwelling rates than in the west, as shown by radionuclide concentrations. To gain insight to long-term changes in the Weddell Gyre, nutrient concentrations can also be investigated as oceanic tracers. We determine long-term trends in surface silicates, a necessary nutrient for silicifying phytoplankton, from ship-based measurements since 1996, and find that the strongest increase is found in the central western sub-gyre region. In association with the eastern sub-gyre, long-term trends along the Prime Meridian are strongest (albeit weaker than in the central western sub-gyre) in the westward flowing southern limb of the gyre, downstream of Maud Rise. We hypothesize that there are different dynamical drivers, such as wind-driven upwelling (west) and turbulent mixing (east), which cause the positive silicate trends in the east versus the west, which are investigated accordingly.

How to cite: Reeve, K. A., Hoppema, M., Kanzow, T., Boebel, O., Geibert, W., and Strass, V.: The Weddell Gyre: what drives a long-term increase in surface nutrients?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8176, https://doi.org/10.5194/egusphere-egu23-8176, 2023.