scholarly journals Marine Ecosystem Dynamics and Biogeochemical Cycling in the Community Earth System Model [CESM1(BGC)]: Comparison of the 1990s with the 2090s under the RCP4.5 and RCP8.5 Scenarios

2013 ◽  
Vol 26 (23) ◽  
pp. 9291-9312 ◽  
Author(s):  
J. Keith Moore ◽  
Keith Lindsay ◽  
Scott C. Doney ◽  
Matthew C. Long ◽  
Kazuhiro Misumi
Keyword(s):  
Climate Change ◽  
Ocean Circulation ◽  
Marine Ecosystem ◽  
Earth System Model ◽  
Ecosystem Dynamics ◽  
System Model ◽  
Earth System ◽  
Production Scale ◽  
Export Production ◽  
Community Earth System Model

The authors compare Community Earth System Model results to marine observations for the 1990s and examine climate change impacts on biogeochemistry at the end of the twenty-first century under two future scenarios (Representative Concentration Pathways RCP4.5 and RCP8.5). Late-twentieth-century seasonally varying mixed layer depths are generally within 10 m of observations, with a Southern Ocean shallow bias. Surface nutrient and chlorophyll concentrations exhibit positive biases at low latitudes and negative biases at high latitudes. The volume of the oxygen minimum zones is overestimated. The impacts of climate change on biogeochemistry have similar spatial patterns under RCP4.5 and RCP8.5, but perturbation magnitudes are larger under RCP8.5. Increasing stratification leads to weaker nutrient entrainment and decreased primary and export production (>30% over large areas). The global-scale decreases in primary and export production scale linearly with the increases in mean sea surface temperature. There are production increases in the high nitrate, low chlorophyll (HNLC) regions, driven by lateral iron inputs from adjacent areas. The increased HNLC export partially compensates for the reductions in non-HNLC waters (~25% offset). Stabilizing greenhouse gas emissions and climate by the end of this century (as in RCP4.5) will minimize the changes to nutrient cycling and primary production in the oceans. In contrast, continued increasing emission of CO2 (as in RCP8.5) will lead to reduced productivity and significant modifications to ocean circulation and biogeochemistry by the end of this century, with more drastic changes beyond the year 2100 as the climate continues to rapidly warm.

scholarly journals <sup>231</sup>Pa and <sup>230</sup>Th in the ocean model of the Community Earth System Model (CESM1.3)

2017 ◽  
Vol 10 (12) ◽  
pp. 4723-4742 ◽  
Author(s):  
Sifan Gu ◽  
Zhengyu Liu
Keyword(s):  
Ocean Circulation ◽  
Activity Ratio ◽  
Marine Ecosystem ◽  
Deep Ocean ◽  
Ocean Model ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Direct Model ◽  
Community Earth System Model

Abstract. The sediment 231Pa ∕ 230Th activity ratio is emerging as an important proxy for deep ocean circulation in the past. In order to allow for a direct model–data comparison and to improve our understanding of the sediment 231Pa ∕ 230Th activity ratio, we implement 231Pa and 230Th in the ocean component of the Community Earth System Model (CESM). In addition to the fully coupled implementation of the scavenging behavior of 231Pa and 230Th with the active marine ecosystem module (particle-coupled: hereafter p-coupled), another form of 231Pa and 230Th have also been implemented with prescribed particle flux fields of the present climate (particle-fixed: hereafter p-fixed). The comparison of the two forms of 231Pa and 230Th helps to isolate the influence of the particle fluxes from that of ocean circulation. Under present-day climate forcing, our model is able to simulate water column 231Pa and 230Th activity and the sediment 231Pa ∕ 230Th activity ratio in good agreement with available observations. In addition, in response to freshwater forcing, the p-coupled and p-fixed sediment 231Pa ∕ 230Th activity ratios behave similarly over large areas of low productivity on long timescales, but can differ substantially in some regions of high productivity and on short timescales, indicating the importance of biological productivity in addition to ocean transport. Therefore, our model provides a potentially powerful tool to help the interpretation of sediment 231Pa ∕ 230Th reconstructions and to improve our understanding of past ocean circulation and climate changes.

scholarly journals Neodymium isotopes in the ocean model of the Community Earth System Model (CESM1.3)

2017 ◽  
Author(s):  
Sifan Gu ◽  
Zhengyu Liu ◽  
Alexandra Jahn ◽  
Johannes Rempfer ◽  
Jiaxu Zhang ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Climate Models ◽  
Marine Ecosystem ◽  
Ocean Model ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Promising Tool ◽  
Boundary Source ◽  
Community Earth System Model

Abstract. Neodymium (Nd) isotope ratio (εNd) is a quasi-conservative water mass tracer and has been used increasingly as paleoclimate proxy to indicate the past evolution of ocean circulation. However, there are many uncertainties in interpreting εNd reconstructions. For the purposes of direct comparison between climate models and proxy reconstructions, we implement Nd isotopes (143Nd and 144Nd) in the ocean model of the Community Earth System Model (CESM). Two versions of Nd tracers are implemented: one is the "abiotic" Nd in which the particle fields are prescribed as the particle climatology generated by the marine ecosystem module of the CESM under present day forcing; the other is the "biotic" Nd that is coupled with the marine ecosystem module. Under present day climate forcing, our model is able to simulate both Nd concentrations and εNd in good agreement with available observations. Also, Nd concentration and εNd in our model show similar sensitivities to the total boundary source and the ratio between particle related Nd and dissolved Nd as in previous modeling study (Rempfer et al., 2011). Therefore, our Nd-enabled ocean model provides a promising tool to study past changes in ocean and climate.

scholarly journals <sup>231</sup>Pa and <sup>230</sup>Th in the ocean model of the Community Earth System Model (CESM1.3)

2017 ◽  
Author(s):  
Sifan Gu ◽  
Zhengyu Liu
Keyword(s):  
Ocean Circulation ◽  
Activity Ratio ◽  
Marine Ecosystem ◽  
Deep Ocean ◽  
Ocean Model ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Direct Model ◽  
Community Earth System Model

Abstract. Sediment 231Pa/230Th activity ratio is emerging as an important proxy for deep ocean circulation in the past. In order to allow for a direct model-data comparison and to improve our understanding of sediment 231Pa/230Th activity ratio, we implement 231Pa and 230Th in the ocean component of the Community Earth System Model (CESM). In addition to the biotic 231Pa and 230Th that is fully coupled with the active marine ecosystem module, another form of abiotic 231Pa and 230Th have also been implemented with prescribed particle flux fields of the present climate. The comparison of the two forms of 231Pa and 230Th helps to isolate the influence of the particle fluxes from that of circulation. Under present day climate forcing, our model is able to simulate water column 231Pa and 230Th activity and sediment 231Pa/230Th activity ratio in good agreement with available observations. For past climate, our model is able to simulate a comparable magnitude of the change of sediment 231Pa/230Th activity ratio between the state with and without active AMOC in reconstruction. In addition, in hosing experiments, the biotic and abiotic sediment 231Pa/230Th activity ratios behave similarly over large areas of low productivity, but can differ substantially in some regions of high productivity, indicating the importance of biological productivity in addition to physical circulation. Therefore, our model provides a potentially powerful tool to help our interpretation of sediment 231Pa/230Th reconstructions and to improve our understanding of past ocean circulation and climate changes.

scholarly journals The iron budget in ocean surface waters in the 20th and 21st centuries: projections by the Community Earth System Model version 1

2013 ◽  
Vol 10 (5) ◽  
pp. 8505-8559 ◽  
Author(s):  
K. Misumi ◽  
K. Lindsay ◽  
J. K. Moore ◽  
S. C. Doney ◽  
F. O. Bryan ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Surface Waters ◽  
Ocean Surface ◽  
Equatorial Pacific ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Iron Supply ◽  
Eastern Equatorial Pacific ◽  
Community Earth System Model

Abstract. We investigated the simulated iron budget in ocean surface waters in the 1990s and 2090s using the Community Earth System Model version 1 and the Representative Concentration Pathway 8.5 future CO2 emission scenario. We assumed that exogenous iron inputs did not change during the whole simulation period; thus, iron budget changes were attributed solely to changes in ocean circulation and mixing in response to projected global warming. The model simulated the major features of ocean circulation and dissolved iron distribution for the present climate reasonably well. Detailed iron budget analysis revealed that roughly 70% of the iron supplied to surface waters in high-nutrient, low-chlorophyll (HNLC) regions is contributed by ocean circulation and mixing processes, but the dominant supply mechanism differed in each HNLC region: vertical mixing in the Southern Ocean, upwelling in the eastern equatorial Pacific, and deposition of iron-bearing dust in the subarctic North Pacific. In the 2090s, our model projected an increased iron supply to HNLC surface waters, even though enhanced stratification was predicted to reduce iron entrainment from deeper waters. This unexpected result could be attributed largely to changes in the meridional overturning and gyre-scale circulations that intensified the advective supply of iron to surface waters, especially in the eastern equatorial Pacific. The simulated primary and export productions in the 2090s decreased globally by 6% and 13%, respectively, whereas in the HNLC regions, they increased by 11% and 6%, respectively. Roughly half of the elevated production could be attributed to the intensified iron supply. The projected ocean circulation and mixing changes are consistent with recent observations of responses to the warming climate and with other Coupled Model Intercomparison Project model projections. We conclude that future ocean circulation and mixing changes will likely elevate the iron supply to HNLC surface waters and will potentially buffer future reductions in ocean productivity. External inputs of iron to the oceans are likely to be modified with climate change. Future work must incorporate robust estimates of these processes affecting the marine iron cycle.

scholarly journals Projecting climate change in South America using variable‐resolution Community Earth System Model: An application to Chile

2021 ◽  
Author(s):  
Nicolas E. Bambach ◽  
Alan M. Rhoades ◽  
Benjamin J. Hatchett ◽  
Andrew D. Jones ◽  
Paul A. Ullrich ◽  
...  
Keyword(s):  
Climate Change ◽  
South America ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Variable Resolution ◽  
Community Earth System Model

scholarly journals The iron budget in ocean surface waters in the 20th and 21st centuries: projections by the Community Earth System Model version 1

2014 ◽  
Vol 11 (1) ◽  
pp. 33-55 ◽  
Author(s):  
K. Misumi ◽  
K. Lindsay ◽  
J. K. Moore ◽  
S. C. Doney ◽  
F. O. Bryan ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Surface Waters ◽  
Ocean Surface ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Model Version ◽  
Iron Supply ◽  
Community Earth System Model ◽  
Project Model

Abstract. We investigated the simulated iron budget in ocean surface waters in the 1990s and 2090s using the Community Earth System Model version 1 and the Representative Concentration Pathway 8.5 future CO2 emission scenario. We assumed that exogenous iron inputs did not change during the whole simulation period; thus, iron budget changes were attributed solely to changes in ocean circulation and mixing in response to projected global warming, and the resulting impacts on marine biogeochemistry. The model simulated the major features of ocean circulation and dissolved iron distribution for the present climate. Detailed iron budget analysis revealed that roughly 70% of the iron supplied to surface waters in high-nutrient, low-chlorophyll (HNLC) regions is contributed by ocean circulation and mixing processes, but the dominant supply mechanism differed by region: upwelling in the eastern equatorial Pacific and vertical mixing in the Southern Ocean. For the 2090s, our model projected an increased iron supply to HNLC waters, even though enhanced stratification was predicted to reduce iron entrainment from deeper waters. This unexpected result is attributed largely to changes in gyre-scale circulations that intensified the advective supply of iron to HNLC waters. The simulated primary and export production in the 2090s decreased globally by 6 and 13%, respectively, whereas in the HNLC regions, they increased by 11 and 6%, respectively. Roughly half of the elevated production could be attributed to the intensified iron supply. The projected ocean circulation and mixing changes are consistent with recent observations of responses to the warming climate and with other Coupled Model Intercomparison Project model projections. We conclude that future ocean circulation has the potential to increase iron supply to HNLC waters and will potentially buffer future reductions in ocean productivity.

scholarly journals The Atlantic's freshwater budget under climate change in the Community Earth System Model with strongly eddying oceans

Ocean Science ◽  
2021 ◽  
Vol 17 (3) ◽  
pp. 729-754
Author(s):  
André Jüling ◽  
Xun Zhang ◽  
Daniele Castellana ◽  
Anna S. von der Heydt ◽  
Henk A. Dijkstra
Keyword(s):  
Climate Change ◽  
Earth System Model ◽  
Meridional Overturning Circulation ◽  
Multiple Equilibrium ◽  
System Model ◽  
Earth System ◽  
Basin Scale ◽  
Community Earth System Model ◽  
Freshwater Budget ◽  
Resolution Simulation

Abstract. We investigate the freshwater budget of the Atlantic and Arctic oceans in coupled climate change simulations with the Community Earth System Model and compare a strongly eddying setup with 0.1∘ ocean grid spacing to a non-eddying 1∘ configuration typical of Coupled Model Intercomparison Project phase 6 (CMIP6) models. Details of this budget are important to understand the evolution of the Atlantic Meridional Overturning Circulation (AMOC) under climate change. We find that the slowdown of the AMOC in the year 2100 under the increasing CO2 concentrations of the Representative Concentration Pathway 8.5 (RCP8.5) scenario is almost identical between both simulations. Also, the surface freshwater fluxes are similar in their mean and trend under climate change in both simulations. While the basin-scale total freshwater transport is similar between the simulations, significant local differences exist. The high-ocean-resolution simulation exhibits significantly reduced ocean state biases, notably in the salt distribution, due to an improved circulation. Mesoscale eddies contribute considerably to the freshwater and salt transport, in particular at the boundaries of the subtropical and subpolar gyres. Both simulations start in the single equilibrium AMOC regime according to a commonly used AMOC stability indicator and evolve towards the multiple equilibrium regime under climate change, but only the high-resolution simulation enters it due to the reduced biases in the freshwater budget.

scholarly journals The Atlantic's Freshwater Budget under Climate Change in the Community Earth System Model with Strongly Eddying Oceans

2020 ◽  
Author(s):  
André Jüling ◽  
Xun Zhang ◽  
Daniele Castellana ◽  
Anna S. von der Heydt ◽  
Henk A. Dijkstra
Keyword(s):  
Climate Change ◽  
Earth System Model ◽  
Meridional Overturning Circulation ◽  
Multiple Equilibrium ◽  
System Model ◽  
Earth System ◽  
Basin Scale ◽  
Community Earth System Model ◽  
Freshwater Budget ◽  
Resolution Simulation

Abstract. We investigate the freshwater and salinity budget of the Atlantic and Arctic oceans in a strongly eddying coupled climate change simulation with the Community Earth System Model (CESM) and compare it to a simulation with a coarse ocean resolution CESM configuration, typical of CMIP6 models. Details of these budgets are important to understand the evolution of the Atlantic Meridional Overturning Circulation (AMOC) under climate change. We find that the slowdown of the AMOC in 2100 under the increasing CO2 concentrations of the RCP8.5 scenario is almost identical between both simulations. Also, the surface freshwater fluxes are similar in their mean and trend under climate change in both simulations. While the basin-scale total freshwater transport is similar between the simulations, significant local differences exist. The high ocean resolution simulation exhibits significantly reduced ocean state biases, notably in the salt distribution, due to an improved circulation. Mesoscale eddies contribute considerably to the freshwater and salt transport, in particular at the boundary of the subtropical and subpolar gyres. Both simulations start in the single equilibrium AMOC regime according to a commonly used AMOC stability indicator and evolve towards the multiple equilibrium regime under climate change, but only the high resolution simulation enters it due to the reduced biases in the freshwater budget.

The Community Earth System Model (CESM) Large Ensemble Project: A Community Resource for Studying Climate Change in the Presence of Internal Climate Variability

2015 ◽  
Vol 96 (8) ◽  
pp. 1333-1349 ◽  
Author(s):  
J. E. Kay ◽  
C. Deser ◽  
A. Phillips ◽  
A. Mai ◽  
C. Hannay ◽  
...  
Keyword(s):  
Climate Change ◽  
Climate Variability ◽  
Model Error ◽  
Earth System Model ◽  
First Century ◽  
System Model ◽  
Earth System ◽  
Large Ensemble ◽  
Internal Climate Variability ◽  
Community Earth System Model

Abstract While internal climate variability is known to affect climate projections, its influence is often underappreciated and confused with model error. Why? In general, modeling centers contribute a small number of realizations to international climate model assessments [e.g., phase 5 of the Coupled Model Intercomparison Project (CMIP5)]. As a result, model error and internal climate variability are difficult, and at times impossible, to disentangle. In response, the Community Earth System Model (CESM) community designed the CESM Large Ensemble (CESM-LE) with the explicit goal of enabling assessment of climate change in the presence of internal climate variability. All CESM-LE simulations use a single CMIP5 model (CESM with the Community Atmosphere Model, version 5). The core simulations replay the twenty to twenty-first century (1920–2100) 30 times under historical and representative concentration pathway 8.5 external forcing with small initial condition differences. Two companion 1000+-yr-long preindustrial control simulations (fully coupled, prognostic atmosphere and land only) allow assessment of internal climate variability in the absence of climate change. Comprehensive outputs, including many daily fields, are available as single-variable time series on the Earth System Grid for anyone to use. Early results demonstrate the substantial influence of internal climate variability on twentieth- to twenty-first-century climate trajectories. Global warming hiatus decades occur, similar to those recently observed. Internal climate variability alone can produce projection spread comparable to that in CMIP5. Scientists and stakeholders can use CESM-LE outputs to help interpret the observational record, to understand projection spread and to plan for a range of possible futures influenced by both internal climate variability and forced climate change.

scholarly journals Climate Change Projection in the Twenty-First Century Simulated by NIMS-KMA CMIP6 Model Based on New GHGs Concentration Pathways

2021 ◽  
Author(s):  
Hyun Min Sung ◽  
Jisun Kim ◽  
Sungbo Shim ◽  
Jeong-byn Seo ◽  
Sang-Hoon Kwon ◽  
...  
Keyword(s):  
Climate Change ◽  
Climate Changes ◽  
Scientific Information ◽  
Earth System Model ◽  
First Century ◽  
System Model ◽  
The Arctic ◽  
Earth System ◽  
Future Projections ◽  
Twenty First Century

AbstractThe National Institute of Meteorological Sciences-Korea Meteorological Administration (NIMS-KMA) has participated in the Coupled Model Inter-comparison Project (CMIP) and provided long-term simulations using the coupled climate model. The NIMS-KMA produces new future projections using the ensemble mean of KMA Advanced Community Earth system model (K-ACE) and UK Earth System Model version1 (UKESM1) simulations to provide scientific information of future climate changes. In this study, we analyze four experiments those conducted following the new shared socioeconomic pathway (SSP) based scenarios to examine projected climate change in the twenty-first century. Present day (PD) simulations show high performance skill in both climate mean and variability, which provide a reliability of the climate models and reduces the uncertainty in response to future forcing. In future projections, global temperature increases from 1.92 °C to 5.20 °C relative to the PD level (1995–2014). Global mean precipitation increases from 5.1% to 10.1% and sea ice extent decreases from 19% to 62% in the Arctic and from 18% to 54% in the Antarctic. In addition, climate changes are accelerating toward the late twenty-first century. Our CMIP6 simulations are released to the public through the Earth System Grid Federation (ESGF) international data sharing portal and are used to support the establishment of the national adaptation plan for climate change in South Korea.

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