scholarly journals Effects of Ocean Biology on the Penetrative Radiation in a Coupled Climate Model

2006 ◽  
Vol 19 (16) ◽  
pp. 3973-3987 ◽  
Author(s):  
Patrick Wetzel ◽  
Ernst Maier-Reimer ◽  
Michael Botzet ◽  
Johann Jungclaus ◽  
Noel Keenlyside ◽  
...  
Keyword(s):  
Seasonal Cycle ◽  
Marine Biology ◽  
Climate Model ◽  
Global Climate ◽  
Ocean Model ◽  
Equatorial Pacific ◽  
Shortwave Radiation ◽  
Upper Ocean ◽  
Biogeochemical Model ◽  
Coupled Climate Model

Abstract The influence of phytoplankton on the seasonal cycle and the mean global climate is investigated in a fully coupled climate model. The control experiment uses a fixed attenuation depth for shortwave radiation, while the attenuation depth in the experiment with biology is derived from phytoplankton concentrations simulated with a marine biogeochemical model coupled online to the ocean model. Some of the changes in the upper ocean are similar to the results from previous studies that did not use interactive atmospheres, for example, amplification of the seasonal cycle; warming in upwelling regions, such as the equatorial Pacific and the Arabian Sea; and reduction in sea ice cover in the high latitudes. In addition, positive feedbacks within the climate system cause a global shift of the seasonal cycle. The onset of spring is about 2 weeks earlier, which results in a more realistic representation of the seasons. Feedback mechanisms, such as increased wind stress and changes in the shortwave radiation, lead to significant warming in the midlatitudes in summer and to seasonal modifications of the overall warming in the equatorial Pacific. Temperature changes also occur over land where they are sometimes even larger than over the ocean. In the equatorial Pacific, the strength of interannual SST variability is reduced by about 10%–15% and phase locking to the annual cycle is improved. The ENSO spectral peak is broader than in the experiment without biology and the dominant ENSO period is increased to around 5 yr. Also the skewness of ENSO variability is slightly improved. All of these changes lead to the conclusion that the influence of marine biology on the radiative budget of the upper ocean should be considered in detailed simulations of the earth’s climate.

scholarly journals Dynamic Downscaling of the Impact of Climate Change on the Ocean Circulation in the Galápagos Archipelago

2013 ◽  
Vol 2013 ◽  
pp. 1-18 ◽  
Author(s):  
Yanyun Liu ◽  
Lian Xie ◽  
John M. Morrison ◽  
Daniel Kamykowski
Keyword(s):  
Climate Change ◽  
Ocean Circulation ◽  
Global Climate Change ◽  
Climate Model ◽  
Global Climate ◽  
Ocean Model ◽  
Reanalysis Dataset ◽  
Equatorial Undercurrent ◽  
Galapagos Archipelago ◽  
The Impact

The regional impact of global climate change on the ocean circulation around the Galápagos Archipelago is studied using the Hybrid Coordinate Ocean Model (HYCOM) configured for a four-level nested domain system. The modeling system is validated and calibrated using daily atmospheric forcing derived from the NCEP/NCAR reanalysis dataset from 1951 to 2007. The potential impact of future anthropogenic global warming (AGW) in the Galápagos region is examined using the calibrated HYCOM with forcing derived from the IPCC-AR4 climate model. Results show that although the oceanic variability in the entire Galápagos region is significantly affected by global climate change, the degree of such effects is inhomogeneous across the region. The upwelling region to the west of the Isabella Island shows relatively slower warming trends compared to the eastern Galápagos region. Diagnostic analysis suggests that the variability in the western Galápagos upwelling region is affected mainly by equatorial undercurrent (EUC) and Panama currents, while the central/east Galápagos is predominantly affected by both Peru and EUC currents. The inhomogeneous responses in different regions of the Galápagos Archipelago to future AGW can be explained by the incoherent changes of the various current systems in the Galápagos region as a result of global climate change.

Heinrich Stadials: Globa Climate Impacts and the "Bipolar Seesaw" Phase Relationsip

2020 ◽  
Author(s):  
Richard Peltier ◽  
Jesse velay-Vitow ◽  
Deepak Chandan
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Phase Relationship ◽  
Coupled Model ◽  
Ice Cores ◽  
Climate Impacts ◽  
Coupled Climate Model ◽  
Heinrich Event ◽  
Freshwater Forcing ◽  
Isotopic Records

<p>With the recent demonstration that millennial timescale Dansgaard-Oeschger oscillations of MIS 3 are predictable in a modern coupled climate model following a Heinrich event-like reduction of AMOC strength (eg. Peltier and Vettoretti, 2014), the stage was set for a renewed attack upon the physics of H-events themselves (see Velay-Vitow et al, 2019, JGR-Oceans). This predicts that the freshwater forcing of the AMOC by individual H-events will be on the order of 0.1 Sv and to be maintained for a period between 500 years and 1500 years in accord with data-based inferences (Hemming, 2004). Whereas in the original analysis of H-event induced D-O oscillations the D-O initiating H-event appeared simply as a sharp reduction in AMOC strength in the spin-up of the coupled model, in the work to be reported we transform the pseudo H-event into one that involves explicit freshwater forcing applied at a strength and over a range of times in accord with observational constraints. This has enabled a detailed analysis of the global climate impacts of these events as represented in the coupled climate model that we continue to employ. A critical focus of this analysis is upon the phase relationship between events recorded in the oxygen isotopic records from Greenland and Antarctic ice cores, analyses which demonstrate that this phase relationship is set by the D-O initiating Heinrich event. We also address the expected global climate impacts of stadial-interstadial transitions and provide an initial discussion of these impacts with those recorded in speliothems and other archives.</p>

Could the cloud cover in future climate models be improved by incorporating the role of sea spray in surface heat fluxes?

2020 ◽  
Author(s):  
Yajuan Song ◽  
Fangli Qiao ◽  
Qi Shu ◽  
Jiping Liu ◽  
Ying Bao ◽  
...  
Keyword(s):  
Latent Heat ◽  
Cloud Cover ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Heat Fluxes ◽  
Global Climate Models ◽  
Shortwave Radiation ◽  
Sea Spray ◽  
Low Level

<p>Accurate cloud cover and radiative effect simulation remains a long-standing challenge for global climate models (GCMs). The Southern Ocean (SO) cloud cover is substantially underestimated by most GCMs. Therefore, too much shortwave radiation is absorbed by oceans, which causes an overly warm sea surface temperature (SST) bias over the SO. For the first time, sea spray effects on latent and sensible heat fluxes are considered in a climate model. The most notable sea spray impacts on heat fluxes occur over the SO, with anomalous latent heat fluxes up to -7.74 W m<sup>-2</sup>. Enhanced latent heat release lead to SST cooling. In addition, more clouds are formed over the SO to reflect excessive downward shortwave radiation, especially low-level clouds at 1.51% increments. Our results provide a feasible solution to mitigate the lack of low-level clouds and overly warm SST biases over the SO in GCMs.</p>

scholarly journals Formulation of an ocean model for global climate simulations

Ocean Science ◽  
2005 ◽  
Vol 1 (1) ◽  
pp. 45-79 ◽  
Author(s):  
S. M. Griffies ◽  
A. Gnanadesikan ◽  
K. W. Dixon ◽  
J. P. Dunne ◽  
R. Gerdes ◽  
...  
Keyword(s):  
Free Surface ◽  
Climate Model ◽  
Global Climate ◽  
Three Dimensional ◽  
Ocean Model ◽  
Tidal Mixing ◽  
The Arctic ◽  
Tracer Transport ◽  
Marginal Seas ◽  
Ocean Climate Model

Abstract. This paper summarizes the formulation of the ocean component to the Geophysical Fluid Dynamics Laboratory's (GFDL) climate model used for the 4th IPCC Assessment (AR4) of global climate change. In particular, it reviews the numerical schemes and physical parameterizations that make up an ocean climate model and how these schemes are pieced together for use in a state-of-the-art climate model. Features of the model described here include the following: (1) tripolar grid to resolve the Arctic Ocean without polar filtering, (2) partial bottom step representation of topography to better represent topographically influenced advective and wave processes, (3) more accurate equation of state, (4) three-dimensional flux limited tracer advection to reduce overshoots and undershoots, (5) incorporation of regional climatological variability in shortwave penetration, (6) neutral physics parameterization for representation of the pathways of tracer transport, (7) staggered time stepping for tracer conservation and numerical efficiency, (8) anisotropic horizontal viscosities for representation of equatorial currents, (9) parameterization of exchange with marginal seas, (10) incorporation of a free surface that accomodates a dynamic ice model and wave propagation, (11) transport of water across the ocean free surface to eliminate unphysical ``virtual tracer flux" methods, (12) parameterization of tidal mixing on continental shelves. We also present preliminary analyses of two particularly important sensitivities isolated during the development process, namely the details of how parameterized subgridscale eddies transport momentum and tracers.

scholarly journals Formulation of an ocean model for global climate simulations

2005 ◽  
Vol 2 (3) ◽  
pp. 165-246 ◽  
Author(s):  
S. M. Griffies ◽  
A. Gnanadesikan ◽  
K. W. Dixon ◽  
J. P. Dunne ◽  
R. Gerdes ◽  
...  
Keyword(s):  
Free Surface ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Three Dimensional ◽  
Coupled Model ◽  
Ocean Model ◽  
Tidal Mixing ◽  
The Arctic ◽  
Tracer Transport

Abstract. This paper summarizes the formulation of the ocean component to the Geophysical Fluid Dynamics Laboratory's (GFDL) coupled climate model used for the 4th IPCC Assessment (AR4) of global climate change. In particular, it reviews elements of ocean climate models and how they are pieced together for use in a state-of-the-art coupled model. Novel issues are also highlighted, with particular attention given to sensitivity of the coupled simulation to physical parameterizations and numerical methods. Features of the model described here include the following: (1) tripolar grid to resolve the Arctic Ocean without polar filtering, (2) partial bottom step representation of topography to better represent topographically influenced advective and wave processes, (3) more accurate equation of state, (4) three-dimensional flux limited tracer advection to reduce overshoots and undershoots, (5) incorporation of regional climatological variability in shortwave penetration, (6) neutral physics parameterization for representation of the pathways of tracer transport, (7) staggered time stepping for tracer conservation and numerical efficiency, (8) anisotropic horizontal viscosities for representation of equatorial currents, (9) parameterization of exchange with marginal seas, (10) incorporation of a free surface that accomodates a dynamic ice model and wave propagation, (11) transport of water across the ocean free surface to eliminate unphysical "virtual tracer flux" methods, (12) parameterization of tidal mixing on continental shelves.

scholarly journals FORTE 2.0: a fast, parallel and flexible coupled climate model

2021 ◽  
Vol 14 (1) ◽  
pp. 275-293
Author(s):  
Adam T. Blaker ◽  
Manoj Joshi ◽  
Bablu Sinha ◽  
David P. Stevens ◽  
Robin S. Smith ◽  
...  
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Ocean Model ◽  
Coupled Climate Model ◽  
Layer Depth ◽  
Ocean General Circulation ◽  
Modular Ocean Model

Abstract. FORTE 2.0 is an intermediate-resolution coupled atmosphere–ocean general circulation model (AOGCM) consisting of the Intermediate General Circulation Model 4 (IGCM4), a T42 spectral atmosphere with 35σ layers, coupled to Modular Ocean Model – Array (MOMA), a 2∘ × 2∘ ocean with 15 z-layer depth levels. Sea ice is represented by a simple flux barrier. Both the atmosphere and ocean components are coded in Fortran. It is capable of producing a stable climate for long integrations without the need for flux adjustments. One flexibility afforded by the IGCM4 atmosphere is the ability to configure the atmosphere with either 35σ layers (troposphere and stratosphere) or 20σ layers (troposphere only). This enables experimental designs for exploring the roles of the troposphere and stratosphere, and the faster integration of the 20σ layer configuration enables longer duration studies on modest hardware. A description of FORTE 2.0 is given, followed by the analysis of two 2000-year control integrations, one using the 35σ configuration of IGCM4 and one using the 20σ configuration.

High-resolution regional projections of sea level changes along Western European coasts during the 21st century

2021 ◽  
Author(s):  
Alisée Chaigneau ◽  
Guillaume Reffray ◽  
Aurore Voldoire ◽  
Angélique Melet
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Climate Model ◽  
Dynamical Downscaling ◽  
Global Climate ◽  
Ocean Model ◽  
Coastal Processes ◽  
Second Phase ◽  
Climate Change Scenarios ◽  
Sea Level Changes

<p>Coastal regions are subject to an increasing anthropogenic pressure. Projections of coastal sea level changes are of great interest for coastal risk assessment and decision-making processes. Sea level projections are typically produced using global climate models. However, their coarse resolution limits the realism of the representation of coastal dynamical processes influencing sea level changes at the coast, potentially leading to substantial biases. Dynamical downscaling methods can be used to refine projections at regional scales by increasing the model spatial resolution and by explicitly including more processes. Such methods rely on the implementation of a high-resolution regional climate model (RCM). </p><p>In this work, we developed the IBI-CCS regional ocean model based on a 1/12° North Eastern Atlantic NEMO ocean model configuration. IBI-CCS includes coastal processes such as tides and atmospheric pressure forcing in addition to the ocean general circulation (dynamic sea level). This RCM is used to perform a dynamical downscaling of CNRM-CM6-1-HR, a global climate model (GCM) developed by the Centre National de Recherches Météorologiques (CNRM) with a 1/4° resolution over the ocean. CNRM-CM6-1-HR contributes to the Coupled Model Intercomparison Project 6th Phase (CMIP6). IBI-CCS is thus forced by the GCM ocean and atmospheric outputs at the lateral and air-sea boundaries. Several corrections were applied to the GCM forcings to avoid the propagation of climate drifts and biases into the regional simulations. The computations are performed over the 1950 to 2100 period for several CMIP6 climate change scenarios.</p><p>In order to validate the dynamical downscaling method, the regionally downscaled (IBI-CCS) and GCM (CNRM-CM6-1-HR) simulations are compared to reanalyses and observational datasets over the 1993-2014 period. These comparisons are performed at different time scales for a selection of ocean variables including sea level. The results show that large scale performances of IBI-CCS are better than those of the GCM thanks to the corrections applied. In addition, high frequency diagnostics are carried out and highlight for example that IBI-CCS sea level extreme events are similar to those of a reference regional ocean reanalysis. In a second phase, the RCM and GCM sea level rise projections are compared over the 21<sup>st</sup> century. These comparisons allow to investigate the impact of the model resolution and of a more complete representation of coastal processes for the simulation of projected sea level changes. </p>

scholarly journals Tropical Pacific Climate and Its Response to Global Warming in the Kiel Climate Model

2009 ◽  
Vol 22 (1) ◽  
pp. 71-92 ◽  
Author(s):  
W. Park ◽  
N. Keenlyside ◽  
M. Latif ◽  
A. Ströh ◽  
R. Redler ◽  
...  
Keyword(s):  
Global Warming ◽  
Climate Model ◽  
Southern Oscillation ◽  
Global Climate ◽  
Global Climate Model ◽  
Co2 Concentration ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Cold Bias ◽  
The Tropical Pacific

Abstract A new, non-flux-corrected, global climate model is introduced, the Kiel Climate Model (KCM), which will be used to study internal climate variability from interannual to millennial time scales and climate predictability of the first and second kind. The version described here is a coarse-resolution version that will be employed in extended-range integrations of several millennia. KCM’s performance in the tropical Pacific with respect to mean state, annual cycle, and El Niño–Southern Oscillation (ENSO) is described. Additionally, the tropical Pacific response to global warming is studied. Overall, climate drift in a multicentury control integration is small. However, KCM exhibits an equatorial cold bias at the surface of the order 1°C, while strong warm biases of several degrees are simulated in the eastern tropical Pacific on both sides off the equator, with maxima near the coasts. The annual and semiannual cycles are realistically simulated in the eastern and western equatorial Pacific, respectively. ENSO performance compares favorably to observations with respect to both amplitude and period. An ensemble of eight greenhouse warming simulations was performed, in which the CO2 concentration was increased by 1% yr−1 until doubling was reached, and stabilized thereafter. Warming of equatorial Pacific sea surface temperature (SST) is, to first order, zonally symmetric and leads to a sharpening of the thermocline. ENSO variability increases because of global warming: during the 30-yr period after CO2 doubling, the ensemble mean standard deviation of Niño-3 SST anomalies is increased by 26% relative to the control, and power in the ENSO band is almost doubled. The increased variability is due to both a strengthened (22%) thermocline feedback and an enhanced (52%) atmospheric sensitivity to SST; both are associated with changes in the basic state. Although variability increases in the mean, there is a large spread among ensemble members and hence a finite probability that in the “model world” no change in ENSO would be observed.

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