scholarly journals Surging of Global Surface Temperature due to Decadal Legacy of Ocean Heat Uptake

2020 ◽  
Vol 33 (18) ◽  
pp. 8025-8045
Author(s):  
Bablu Sinha ◽  
Florian Sévellec ◽  
Jon Robson ◽  
A. J. George Nurser
Keyword(s):  
Thermal Gradient ◽  
Climate Model ◽  
Heat Budget ◽  
Global Climate ◽  
Global Climate Model ◽  
Vertical Mixing ◽  
Base Layer ◽  
Ocean Heat Uptake ◽  
Surface Warming ◽  
Global Surface

AbstractGlobal surface warming since 1850 has consisted of a series of slowdowns (hiatus) followed by surges. Knowledge of a mechanism to explain how this occurs would aid development and testing of interannual to decadal climate forecasts. In this paper a global climate model is forced to adopt an ocean state corresponding to a hiatus [with negative interdecadal Pacific oscillation (IPO) and other surface features typical of a hiatus] by artificially increasing the background diffusivity for a decade before restoring it to its normal value and allowing the model to evolve freely. This causes the model to develop a decadal surge that overshoots equilibrium (resulting in a positive IPO state), leaving behind a modified, warmer climate for decades. Water-mass transformation diagnostics indicate that the heat budget of the tropical Pacific Ocean is a balance between large opposite-signed terms: surface heating/cooling resulting from air–sea heat flux is balanced by vertical mixing and ocean heat transport divergence. During the artificial hiatus, excess heat becomes trapped just above the thermocline and there is a weak vertical thermal gradient (due to the high artificial background mixing). When the hiatus is terminated, by returning the background diffusivity to normal, the thermal gradient strengthens to prehiatus values so that the mixing (diffusivity × thermal gradient) remains roughly constant. However, since the base layer just above the thermocline remains anomalously warm, this implies a warming of the entire water column above the trapped heat, which results in a surge followed by a prolonged period of elevated surface temperatures.

scholarly journals The Granular Sea Ice Model in Spherical Coordinates and Its Application to a Global Climate Model

2007 ◽  
Vol 20 (24) ◽  
pp. 5946-5961 ◽  
Author(s):  
Jan Sedlacek ◽  
Jean-François Lemieux ◽  
Lawrence A. Mysak ◽  
L. Bruno Tremblay ◽  
David M. Holland
Keyword(s):  
Growth Rate ◽  
Sea Ice ◽  
Climate Model ◽  
Heat Budget ◽  
Global Climate ◽  
Global Climate Model ◽  
Internal Heat ◽  
The Arctic ◽  
Spherical Coordinates ◽  
Ice Model

Abstract The granular sea ice model (GRAN) from Tremblay and Mysak is converted from Cartesian to spherical coordinates. In this conversion, the metric terms in the divergence of the deviatoric stress and in the strain rates are included. As an application, the GRAN is coupled to the global Earth System Climate Model from the University of Victoria. The sea ice model is validated against standard datasets. The sea ice volume and area exported through Fram Strait agree well with values obtained from in situ and satellite-derived estimates. The sea ice velocity in the interior Arctic agrees well with buoy drift data. The thermodynamic behavior of the sea ice model over a seasonal cycle at one location in the Beaufort Sea is validated against the Surface Heat Budget of the Arctic Ocean (SHEBA) datasets. The thermodynamic growth rate in the model is almost twice as large as the observed growth rate, and the melt rate is 25% lower than observed. The larger growth rate is due to thinner ice at the beginning of the SHEBA period and the absence of internal heat storage in the ice layer in the model. The simulated lower summer melt is due to the smaller-than-observed surface melt.

scholarly journals A Standardized Global Climate Model Study Showing Unique Properties for the Climate Response to Black Carbon Aerosols

2015 ◽  
Vol 28 (6) ◽  
pp. 2512-2526 ◽  
Author(s):  
M. Sand ◽  
T. Iversen ◽  
P. Bohlinger ◽  
A. Kirkevåg ◽  
I. Seierstad ◽  
...  
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
Climate Model ◽  
Kernel Method ◽  
Global Climate ◽  
Global Climate Model ◽  
Climate Response ◽  
Air Concentration ◽  
Surface Warming ◽  
The Difference

Abstract The climate response to an abrupt increase of black carbon (BC) aerosols is compared to the standard CMIP5 experiment of quadrupling CO2 concentrations in air. The global climate model NorESM with interactive aerosols is used. One experiment employs prescribed BC emissions with calculated concentrations coupled to atmospheric processes (emission-driven) while a second prescribes BC concentrations in air (concentration-driven) from a precalculation with the same model and emissions, but where the calculated BC does not force the climate dynamics. The difference quantifies effects of feedbacks between airborne BC and other climate processes. BC emissions are multiplied with 25, yielding an instantaneous top-of-atmosphere (TOA) radiative forcing (RF) comparable to the quadrupling of atmospheric CO2. A radiative kernel method is applied to estimate the different feedbacks. In both BC runs, BC leads to a much smaller surface warming than CO2. Rapid atmospheric feedbacks reduce the BC-induced TOA forcing by approximately 75% over the first year (10% for CO2). For BC, equilibrium is quickly re-established, whereas for CO2 equilibration requires a much longer time than 150 years. Emission-driven BC responses in the atmosphere are much larger than the concentration-driven. The northward displacement of the intertropical convergence zone (ITCZ) in the BC emission-driven experiment enhances both the vertical transport and deposition of BC from Southeast Asia. The study shows that prescribing BC concentrations may lead to seriously inaccurate conclusions, but other models with less efficient transport may produce results with smaller differences.

scholarly journals The SMHI Large Ensemble (SMHI-LENS) with EC-Earth3

2021 ◽  
Author(s):  
Klaus Wyser ◽  
Torben Koenigk ◽  
Uwe Fladrich ◽  
Ramon Fuentes-Franco ◽  
Mehdi Pasha Karami ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Large Ensemble ◽  
Sea Level Pressure ◽  
Near Surface ◽  
Surface Warming ◽  
Key Variables ◽  
Set Up

Abstract. The Swedish Meteorological and Hydrological Institute used the global climate model EC-Earth3 to perform a large ensemble of simulations (SMHI-LENS). It consists of 50 members, covers the period 1970 to 2100 and comprises the SSP1-1.9, SSP3-3.4, SSP5-3.4-OS and SSP5-8.5 scenarios. Thus, it is currently the only large ensemble that allows for analyzing the effect of delayed mitigation actions versus no mitigation efforts and versus earlier efforts leading to similar radiative forcing at year 2100. We describe the set-up of the SMHI-LENS in detail and provide first examples for its application. The ensemble mean future changes of key variables in atmosphere and ocean are analyzed and compared against the variability across the ensemble members. In agreement with other large ensemble simulations, we find that the future changes in the near surface temperature are more robust than those for precipitation or sea level pressure. As an example for a possible application of the SMHI-LENS, we analyse the probability of exceeding specific global surface warming levels in the different scenarios. None of the scenarios is able to keep global warming in the 21st century below 1.5 °C. In SSP1-1.9 there is a probability of approximately 70 % to stay below 2 °C warming while all other SSPs exceed this target in every single member of SMHI-LENS during the course of the century. We also investigate the point in time when the SSP5-8.5 and SSP5-3.4 ensembles separate, i.e. when their differences become significant, and likewise when the SSP5-3.4-OS and SSP4-3.4 ensembles become similar. Last, we show that the time of emergence of a separation between different scenarios can vary by several decades when reducing the ensemble size to 10 members.

Mechanisms of Southern Ocean Heat Uptake and Transport in a Global Eddying Climate Model

2016 ◽  
Vol 29 (6) ◽  
pp. 2059-2075 ◽  
Author(s):  
Adele K. Morrison ◽  
Stephen M. Griffies ◽  
Michael Winton ◽  
Whit G. Anderson ◽  
Jorge L. Sarmiento
Keyword(s):  
Southern Ocean ◽  
Heat Transport ◽  
Climate Model ◽  
Heat Budget ◽  
Global Climate Model ◽  
Heat Content ◽  
Ocean Heat Uptake ◽  
The North ◽  
Heat Uptake ◽  
Mixed Layers

Abstract The Southern Ocean plays a dominant role in anthropogenic oceanic heat uptake. Strong northward transport of the heat content anomaly limits warming of the sea surface temperature in the uptake region and allows the heat uptake to be sustained. Using an eddy-rich global climate model, the processes controlling the northward transport and convergence of the heat anomaly in the midlatitude Southern Ocean are investigated in an idealized 1% yr−1 increasing CO2 simulation. Heat budget analyses reveal that different processes dominate to the north and south of the main convergence region. The heat transport northward from the uptake region in the south is driven primarily by passive advection of the heat content anomaly by the existing time mean circulation, with a smaller 20% contribution from enhanced upwelling. The heat anomaly converges in the midlatitude deep mixed layers because there is not a corresponding increase in the mean heat transport out of the deep mixed layers northward into the mode waters. To the north of the deep mixed layers, eddy processes drive the warming and account for nearly 80% of the northward heat transport anomaly. The eddy transport mechanism results from a reduction in both the diffusive and advective southward eddy heat transports, driven by decreasing isopycnal slopes and decreasing along-isopycnal temperature gradients on the northern edge of the peak warming.

scholarly journals The SMHI Large Ensemble (SMHI-LENS) with EC-Earth3.3.1

2021 ◽  
Vol 14 (7) ◽  
pp. 4781-4796
Author(s):  
Klaus Wyser ◽  
Torben Koenigk ◽  
Uwe Fladrich ◽  
Ramon Fuentes-Franco ◽  
Mehdi Pasha Karami ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Large Ensemble ◽  
Sea Level Pressure ◽  
Near Surface ◽  
Surface Warming ◽  
Key Variables ◽  
Set Up

Abstract. The Swedish Meteorological and Hydrological Institute used the global climate model EC-Earth3 to perform a large ensemble of simulations (SMHI-LENS). It consists of 50 members, covers the period 1970 to 2100, and comprises the SSP1-1.9, SSP3-3.4, SSP5-3.4-OS, and SSP5-8.5 scenarios. Thus, it is currently the only large ensemble that allows for analyzing the effect of delayed mitigation actions versus no mitigation efforts and versus earlier efforts leading to similar radiative forcing at the year 2100. We describe the set-up of the SMHI-LENS in detail and provide first examples of its application. The ensemble mean future changes in key variables in the atmosphere and ocean are analyzed and compared against the variability across the ensemble members. In agreement with other large-ensemble simulations, we find that the future changes in the near-surface temperature are more robust than those for precipitation or sea level pressure. As an example of a possible application of the SMHI-LENS, we analyze the probability of exceeding specific global surface warming levels in the different scenarios. None of the scenarios is able to keep global warming in the 21st century below 1.5 ∘C. In SSP1-1.9 there is a probability of approximately 70 % to stay below 2 ∘C warming, while all other SSPs exceed this target in every single member of SMHI-LENS during the course of the century. We also investigate the point in time when the SSP5-8.5 and SSP5-3.4 ensembles separate, i.e., when their differences become significant, and likewise when the SSP5-3.4-OS and SSP4-3.4 ensembles become similar. Last, we show that the time of emergence of a separation between different scenarios can vary by several decades when reducing the ensemble size to 10 members.

High bit rate ACTS experiments for performing global science - Keck Telescope and global climate model

1996 ◽  
Author(s):  
Larry Bergman ◽  
J. Gary ◽  
Burt Edelson ◽  
Neil Helm ◽  
Judith Cohen ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Bit Rate ◽  
Global Science ◽  
High Bit Rate

scholarly journals A comparison of ship and satellite measurements of cloud properties with global climate model simulations in the southeast Pacific stratus deck

2010 ◽  
Vol 10 (14) ◽  
pp. 6527-6536 ◽  
Author(s):  
M. A. Brunke ◽  
S. P. de Szoeke ◽  
P. Zuidema ◽  
X. Zeng
Keyword(s):  
Diurnal Cycle ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Cloud Fraction ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Cloud Properties ◽  
Southeast Pacific ◽  
Cloud Thickness

Abstract. Here, liquid water path (LWP), cloud fraction, cloud top height, and cloud base height retrieved by a suite of A-train satellite instruments (the CPR aboard CloudSat, CALIOP aboard CALIPSO, and MODIS aboard Aqua) are compared to ship observations from research cruises made in 2001 and 2003–2007 into the stratus/stratocumulus deck over the southeast Pacific Ocean. It is found that CloudSat radar-only LWP is generally too high over this region and the CloudSat/CALIPSO cloud bases are too low. This results in a relationship (LWP~h9) between CloudSat LWP and CALIPSO cloud thickness (h) that is very different from the adiabatic relationship (LWP~h2) from in situ observations. Such biases can be reduced if LWPs suspected to be contaminated by precipitation are eliminated, as determined by the maximum radar reflectivity Zmax>−15 dBZ in the apparent lower half of the cloud, and if cloud bases are determined based upon the adiabatically-determined cloud thickness (h~LWP1/2). Furthermore, comparing results from a global model (CAM3.1) to ship observations reveals that, while the simulated LWP is quite reasonable, the model cloud is too thick and too low, allowing the model to have LWPs that are almost independent of h. This model can also obtain a reasonable diurnal cycle in LWP and cloud fraction at a location roughly in the centre of this region (20° S, 85° W) but has an opposite diurnal cycle to those observed aboard ship at a location closer to the coast (20° S, 75° W). The diurnal cycle at the latter location is slightly improved in the newest version of the model (CAM4). However, the simulated clouds remain too thick and too low, as cloud bases are usually at or near the surface.

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