PP039-05
Shallow and Weak or Shallow and Strong Glacial Atlantic Meridional Overturning Circulation?
Shallow and Weak or Shallow and Strong Glacial Atlantic Meridional Overturning Circulation?
Monday, 14 December 2020: 11:46
Virtual
Abstract:
The characteristics of ocean circulation and deep water mass structure during the Last Glacial Maximum (LGM) is still under debate. Most estimates predict a shallower LGM Atlantic Meridional Overturning Circulation (AMOC) than in the present day, but there is disagreement in the transport rate, with model predictions ranging between a stronger, similar, or weaker strength than today.
Here we use a global ocean physical-biogeochemical model that includes prognostic cycles for carbon isotopes (C-13 and C-14) to generate an ensemble of simulations sampling the two-dimensional phase space of AMOC depth versus strength. Simulated carbon isotopes are directly compared with measurements from deep sea LGM sediments. We find that whereas those data constrain the AMOC depth well, favoring simulations with a shallow (2000-2500 m compared with today's ∼3000 m) AMOC, they provide weaker constraints on AMOC strength. Comparisons with two high vertical resolution LGM δ¹³C profiles suggest LGM AMOC strength between 11 and 17 Sv, but more data of high vertical resolution are needed to refine this estimate. Our LGM estimates are further tested by using them as initial conditions for deglacial simulations, and comparing results with Heinrich Stadial 1 reconstructions.
Here we use a global ocean physical-biogeochemical model that includes prognostic cycles for carbon isotopes (C-13 and C-14) to generate an ensemble of simulations sampling the two-dimensional phase space of AMOC depth versus strength. Simulated carbon isotopes are directly compared with measurements from deep sea LGM sediments. We find that whereas those data constrain the AMOC depth well, favoring simulations with a shallow (2000-2500 m compared with today's ∼3000 m) AMOC, they provide weaker constraints on AMOC strength. Comparisons with two high vertical resolution LGM δ¹³C profiles suggest LGM AMOC strength between 11 and 17 Sv, but more data of high vertical resolution are needed to refine this estimate. Our LGM estimates are further tested by using them as initial conditions for deglacial simulations, and comparing results with Heinrich Stadial 1 reconstructions.