scholarly journals Executive Editor Comment on "An improved land biosphere module for use in reduced complexity Earth System Models with application to the last glacial termination"

2017 ◽  
Author(s):  
Astrid Kerkweg
Keyword(s):  
Earth System ◽  
Editor Comment ◽  
Executive Editor ◽  
System Models ◽  
Last Glacial ◽  
Reduced Complexity ◽  
Earth System Models ◽  
The Last Glacial ◽  
Glacial Termination

scholarly journals Ocean (de)oxygenation from the Last Glacial Maximum to the twenty-first century: insights from Earth System models

2017 ◽  
Vol 375 (2102) ◽  
pp. 20160323 ◽  
Author(s):  
L. Bopp ◽  
L. Resplandy ◽  
A. Untersee ◽  
P. Le Mezo ◽  
M. Kageyama
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Earth System ◽  
Short Term ◽  
System Models ◽  
Last Glacial ◽  
Tropical Oceans ◽  
Earth System Models ◽  
The Last Glacial Maximum ◽  
The Last Glacial

All Earth System models project a consistent decrease in the oxygen content of oceans for the coming decades because of ocean warming, reduced ventilation and increased stratification. But large uncertainties for these future projections of ocean deoxygenation remain for the subsurface tropical oceans where the major oxygen minimum zones are located. Here, we combine global warming projections, model-based estimates of natural short-term variability, as well as data and model estimates of the Last Glacial Maximum (LGM) ocean oxygenation to gain some insights into the major mechanisms of oxygenation changes across these different time scales. We show that the primary uncertainty on future ocean deoxygenation in the subsurface tropical oceans is in fact controlled by a robust compensation between decreasing oxygen saturation (O 2sat ) due to warming and decreasing apparent oxygen utilization (AOU) due to increased ventilation of the corresponding water masses. Modelled short-term natural variability in subsurface oxygen levels also reveals a compensation between O 2sat and AOU, controlled by the latter. Finally, using a model simulation of the LGM, reproducing data-based reconstructions of past ocean (de)oxygenation, we show that the deoxygenation trend of the subsurface ocean during deglaciation was controlled by a combination of warming-induced decreasing O 2sat and increasing AOU driven by a reduced ventilation of tropical subsurface waters. This article is part of the themed issue ‘Ocean ventilation and deoxygenation in a warming world’.

From the last interglacial to the future – new insights from modeling the last glacial-interglacial cycle in PalMod

2021 ◽  
Author(s):  
Kerstin Fieg ◽  
Mojib Latif ◽  
Michael Schulz ◽  
Tatjana Ilyina
Keyword(s):  
Climate Variability ◽  
Ice Sheet ◽  
Earth System ◽  
Glacial Cycle ◽  
System Models ◽  
Last Glacial ◽  
The Future ◽  
Fully Coupled ◽  
Earth System Models ◽  
The Last Glacial

<p>We present new insights from the project PalMod, which started in 2016 and is envisioned to run for a decade. The modelling initiative PalMod aims at filling the long-standing scientific gaps in our understanding of the dynamics and variability of the climate system during the last glacial-interglacial cycle. One of the grand challenges in this context is to quantify the processes that determine the spectrum of climate variability on timescales that range from seasons to millennia. Climatic processes are intimately coupled across these timescales. Understanding variability at any one timescale requires understanding of the whole spectrum. If we could successfully simulate the spectrum of climate variability during the last glacial cycle in Earth system models, would this enable us to more reliably assess the future climate change? Such simulations are necessary to deduce, for example, if a regime shift in climate variability could occur during the next centuries and millennia in response to global warming. PalMod is specifically designed to enhance our understanding of the Earth system dynamics and its variability on timescales up to the multimillennial with complex Earth System Models.</p><p>The following major goals were achieved up to now:</p><ul><li>Full coupling of atmosphere, ocean and ice-sheet models, enabling investigation of Heinrich Events and bi-stability of the AMOC, and millennial-scale transient climate-ice sheet simulations.</li> <li>Implementation of a coupled ocean and land biogeochemistry enabling simulations with prognostic atmospheric CO<sub>2</sub> concentrations and including improved representation of methane (CH<sub>4</sub>) in transient deglaciation runs.</li> <li>Systematic comparison of newly compiled proxy data with model simulations.</li> </ul><p>The major goal for the next two years is to set up the fully coupled physical-biogeochemical model which will be tested for three time periods: deglaciation, glacial inception and Marine Isotope Stage 3 (MIS3). This fully coupled model will be eventually used to simulate the complete glacial cycle and project the climate over the next few millennia.</p>

scholarly journals Comprehensive Earth System Models of the Last Glacial Cycle

Eos ◽  
2016 ◽  
Vol 97 ◽  
Author(s):  
Mojib Latif ◽  
Martin Claussen ◽  
Michael Schulz ◽  
Tim Brücher
Keyword(s):  
Climate Science ◽  
Earth System ◽  
Glacial Cycle ◽  
System Models ◽  
Last Glacial ◽  
Earth System Models ◽  
The Last Glacial

Much of modern climate science fails to consider millennium-scale processes, many of which may prove to be important for predicting the climate trajectory in the shorter term.

scholarly journals An improved land biosphere module for use in reduced complexity Earth System Models with application to the last glacial termination

2017 ◽  
Author(s):  
Roland Eichinger ◽  
Gary Shaffer ◽  
Nelson Albarrán ◽  
Maisa Rojas ◽  
Fabrice Lambert
Keyword(s):  
Carbon Cycling ◽  
Climatic Conditions ◽  
Cold Climate ◽  
Earth System ◽  
Proxy Data ◽  
Last Glacial ◽  
Transition Functions ◽  
Vegetation Zones ◽  
Reduced Complexity ◽  
The Last Glacial

Abstract. Interactions between the land biosphere and the atmosphere play an important role for the Earth's carbon cycle and thus should be considered in studies of global carbon cycling and climate. Simple approaches are a useful first step in this direction but may not be applicable for certain climatic conditions. To improve the ability of the reduced-complexity Danish Center for Earth System Science (DCESS) Earth System Model DCESS to address cold climate conditions, we reformulated the model's land biosphere module by extending it to include three dynamically varying vegetation zones as well as a permafrost component. The vegetation zones are formulated by emulating the behavior of a complex land biosphere model. We show that with the new module, the size and timing of carbon exchanges between atmosphere and land are represented more realistically in cooling and warming experiments. In particular, we use the new module to address carbon cycling and climate change across the last glacial transition. Within the constraints provided by various proxy data records, we tune the DCESS model to a Last Glacial Maximum state and then conduct transient sensitivity experiments across the transition under the application of explicit transition functions for high latitude ocean exchange, atmospheric dust, and the land ice sheet extent. We compare simulated time evolutions of global mean temperature, pCO2, atmospheric and oceanic carbon isotopes as well as ocean dissolved oxygen concentrations with proxy data records. In this way we estimate the importance of different processes across the transition with emphasis on the role of land biosphere variations.

scholarly journals A model-data assessment of the role of Southern Ocean processes in the last glacial termination

2016 ◽  
Author(s):  
Roland Eichinger ◽  
Gary Shaffer ◽  
Nelson Albarrán ◽  
Maisa Rojas ◽  
Fabrice Lambert
Keyword(s):  
Climate Change ◽  
Southern Ocean ◽  
Deep Water ◽  
Atmospheric Temperature ◽  
Earth System ◽  
Proxy Data ◽  
Climate Conditions ◽  
Last Glacial ◽  
The Last Glacial ◽  
Glacial Termination

Abstract. The Southern Ocean has been identified as a key player for the global atmospheric temperature and pCO2 rise across the last glacial termination. One leading hypothesis for explaining the initial pCO2 step of 38 ppm (Mystery Interval 17.5 – 14.5 ka) is enhanced upwelling of Southern Ocean deep water that had stayed isolated from surface layers for millennia, thereby accumulating carbon from remineralisation of organic matter. However, the individual influences involved in this interplay of processes are not fully understood. A credible explanation for this remarkable climate change must also be able to reproduce a simultaneous steep decrease of carbon isotope ratios (δ13C and ∆14C). To address this topic, we here apply the Danish Center for Earth System Science (DCESS) Earth System Model with an improved terrestrial biosphere module and tune it to a glacial steady-state within the constraints provided by various proxy data records. In addition to adjustments of physical and biogeochemical parameters to colder climate conditions, a sharp reduction of the oceanic mixing intensity below around 1800 m depth in the high latitude model ocean is imposed, generating a model analogy to isolated deep water while maintaining this water oxygenated in agreement with proxy data records. From this glacial state, transient sensitivity experiments across the last glacial termination are conducted in order to assess the influence of various mechanisms on the climate change of the Mystery Interval. We show that the upwelling of isolated deep water in the Southern Ocean complemented by several physical and biogeochemical processes can explain parts but not all of the atmospheric variations observed across the Mystery Interval.

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