Sediment fluxes dominate glacial–interglacial changes in ocean carbon inventory: results from factorial simulations over the past 780 000 years

Climate of the past, Journal Year: 2025, Volume and Issue: 21(2), P. 571 - 592

Published: Feb. 28, 2025

Abstract. Atmospheric CO2 concentrations varied over ice age cycles due to net exchange fluxes of carbon between land, ocean, marine sediments, lithosphere, and the atmosphere. Marine sediments polar cores archived indirect biogeochemical evidence these transfers, which resulted from poorly understood responses various reservoirs climate forcing. Modelling studies demonstrated potential several physical processes impact atmospheric under steady-state glacial conditions. However, it remains unclear how much affected cycling during transient changes repeated what role burial release sedimentary organic inorganic nutrients played. Addressing this knowledge gap, we produced a simulation ensemble with idealised cycle forcings inceptions terminations last 780 kyr Bern3D Earth system model intermediate complexity, includes dynamic sediments. The long simulations demonstrate that initiating an interglacial geologic balance causes isotopic drifts require hundreds thousands years overcome. These need be considered when designing spin-up strategies for experiments. Beyond this, our allows us gain process-based understanding resulting associated shifts could serve as proxy data. We present results simulated dynamics in non-equilibrium comparison multiple time series. From draw conclusions. In simulations, cause perturbations have large effects on storage isotopes. Dissolved (DIC) differ by factor up 28 without interactive while atmosphere are 4 times larger simulated. relationship DIC (−1800–1400 GtC) change (−170–190 deglaciation is strongly setup-dependent, highlighting considering multi-proxy analyses more robustly quantify global cycles.

Language: Английский

Generalized stability landscape of the Atlantic meridional overturning circulation

Earth System Dynamics, Journal Year: 2024, Volume and Issue: 15(6), P. 1417 - 1434

Published: Nov. 12, 2024

Abstract. The Atlantic meridional overturning circulation (AMOC) plays a crucial role in shaping climate conditions over the North region and beyond, its future stability is matter of concern. While AMOC when faced with surface freshwater forcing (FWF) has been thoroughly investigated, equilibrium response to changing CO2 remains largely unexplored, precluding comprehensive understanding under global warming. Here we use an Earth system model explore combined changes FWF atmospheric concentrations between 180 560 ppm. We find four different states associated qualitatively convection patterns. Apart from “Off” state no deep-water formation “Modern”-like deep water forming Labrador Nordic seas as observed at present, “Weak” occurring south 55° N “Strong” characterized by extending into Arctic. Off Weak are stable for entire range but only positive FWF. Modern higher than pre-industrial lower negative Finally, Strong above 280 ppm < 0.1 Sv. Generally, strength increases increasing decreases Our landscape helps explain instability colder climates, although it not directly applicable fundamentally transient warming on centennial timescale, can provide useful information about possible long-term fate AMOC. For instance, while monostable model, also becomes ∼ 400 ppm, suggesting that shutdown warmer might be irreversible.

Language: Английский

Surface buoyancy control of millennial-scale variations in the Atlantic meridional ocean circulation

Climate of the past, Journal Year: 2024, Volume and Issue: 20(12), P. 2719 - 2739

Published: Dec. 16, 2024

Abstract. Dansgaard–Oeschger (DO) events are a pervasive feature of glacial climates. It is widely accepted that the associated changes in climate, which most pronounced North Atlantic region, caused by abrupt strength and/or northward extent meridional overturning circulation (AMOC), possibly originating from spontaneous transitions ocean–sea-ice–atmosphere system. Here we use an Earth system model produces DO-like to show climate conditions under millennial-scale AMOC variations occur controlled surface ocean buoyancy flux. In particular, find present-day-like convection pattern with deep-water formation Labrador and Nordic seas becomes unstable when flux integrated over northern turns negative positive. proximity this point between different patterns strong weak states. The depends on freshwater heat fluxes sea temperature through dependence thermal expansion coefficient seawater. We larger ice sheets tend stabilize decreasing net flux, while CO2-induced cooling decreases loss destabilizes convection. These results help explain DO appear step towards improved understanding mechanisms changes.

Language: Английский