Resultados de modelo UVic Ultima Deglaciacion - UVic model output Last Deglaciation V2
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Fecha
Publicador:
Consejo Nacional de Investigaciones Científicas y Técnicas
Fecha de depósito:
21/10/2026
Fecha de creación:
20/10/2026
Clasificación temática
Palabras clave
Resumen
The early last deglaciation (20-15 ka) is characterized by sea level and atmospheric CO2 increase. Changes in ocean circulation, temperature, and dust fluxes have been proposed to transfer carbon from the ocean to the atmosphere, but quantification of these mechanisms is complicated by rapid dynamics and uncertainties of forcings and feedbacks. However, high time resolution tracers may capture some aspects of the processes involved. Here we analyze a global compilation of stable carbon isotope ratios (13C/12C) from benthic foraminifera, which shows enrichment in deep waters of Antarctic origin and depletion in upper North Atlantic Deep Waters during Heinrich Stadial 1. A global climate model is used to attribute effects of three hypothesized forcings: North Atlantic fresh water fluxes, increased Southern Ocean (SO) ventilation, and decreasing atmospheric iron fluxes and export production. We find that SO processes propagate an increase in 13C/12C of dissolved inorganic carbon (DIC) to Antarctic-originated deep waters, in agreement with reconstructions. Conversely, effects of Atlantic Meridional Overturning Circulation (AMOC) changes are small. Our simulations are able to explain early deglacial atmospheric CO2 rise, supporting the importance of SO ventilation and export production to set glacial-interglacial changes in the carbon cycle.
Métodos
We assess the individual effects of different forcings on changes in global ocean distribution of d13C in the 20-15 ka BP interval using different forcings. Our deglacial simulations follow the PMIP phase 4 protocol for deglacial simulations, regarding orbital parameters, ice sheets, river routing, and FWF. Carbon in the atmosphere and ocean are coupled, so CO_2 varies through time. This affects the model's radiative forcing on the ocean, which has an effect on the modeled ocean physics and biogeochemistry. Other trace gases are left constant. Control includes transient changes in land ice sheets calculated after the ICE6G-C reconstruction, which represent an 8 % decrease between 20 and 15 ka BP in the ice sheet volume of the Northern Hemisphere. The effect on the physics of the global ocean in a coarse resolution model due to the changes in orography associated with this reduction in the Northern Hemisphere land ice sheets is very limited. We use Control as the baseline simulation for the rest of deglacial experiments. LDust is as Control but a gradual reduction in atmospheric iron flux is applied. The reduction was calculated by scaling atmospheric soluble iron flux over the SO with the early last deglaciation decrease on dust concentrations determined from Antarctic ice cores. This results in a 85 % decrease between 20 and 15 ka, in line with estimates of deglacial soluble iron flux changes from ice cores and sediment data. LFWF is as Control but surface FWF are applied between 20 and 15 ka in the North Atlantic, North-East Pacific, and SO (around Patagonia), to account for glacier discharge from the melting of land ice sheets. FWF are uniformly applied on grid boxes calculated from a discharge plume map determined from a drainage network model. The total FWF applied is 0.061 Sv, calculated after an estimate of volume equivalent sea level change during the first 3 ka of the last deglaciation, reconstructed from coral and sediment records. Following the drainage model, 93 % of the flux (0.053 Sv) goes into the North Atlantic Ocean, and only 10 and 6 % go into the North-East Pacific and Southern Oceans, respectively. Volume equivalent sea level change reconstructions suggest FWF of 0.061 Sv between 20 and 17 ka BP, and of 0.100 Sv between 17 and 15 ka BP. Applying 0.053 Sv between 20 and 15 ka in the LFWF simulation functions as a lower limit for the effects of FWF to the deglacial ocean. It produces an AMOC that is weaker and shallower than in Control, but is still active. HFWF is as LFWF but the fresh water forcing is increased to 0.087 Sv between 17 and 15 ka, following estimates of volume equivalent sea level change during that interval. In this case, the transport of the AMOC linearly decreases and collapses by 15 ka BP. SOWind is as Control but a 5circ poleward shift and gradual strengthening in the zonal wind velocity and wind stress over the SO are applied. Accounting for more efficient transport over the Southern Ocean in an intensified Westerlies regime, maximum moisture diffusivities are increased by 20 % in the Southern Hemisphere. This results in a meridional moisture flux increase of 12 %. The changes applied follow qualitative estimates of differences between LGM and Holocene wind stress in sup-polar regions. Some of the PMIP models, equipped with a three dimensional atmosphere coupled to the ocean component, predict increased wind stress intensity over the SO after the LGM. The wind changes applied in SOWind serve as a test on the sensitivity of deep ocean tracers to changes in SO ventilation, although these changes could also have been forced by buoyancy fluxes. SOWind_LDust is a combination of the SOWind and LDust simulations. LFWF_SOWind_LDust is a combination of the LFWF and SOWind_LDust simulations. HFWF_SOWind_LDust is a combination of the HFWF and SOWind_LDust simulations.
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