scholarly journals The Influence of Local Feedbacks and Northward Heat Transport on the Equilibrium Arctic Climate Response to Increased Greenhouse Gas Forcing

2012 ◽  
Vol 25 (16) ◽  
pp. 5433-5450 ◽  
Author(s):  
Jennifer E. Kay ◽  
Marika M. Holland ◽  
Cecilia M. Bitz ◽  
Edward Blanchard-Wrigglesworth ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Greenhouse Gas ◽  
Heat Transport ◽  
Ocean Model ◽  
Arctic Climate ◽  
Climate Response ◽  
Surface Climate ◽  
Slab Ocean ◽  
Arctic Surface

Abstract This study uses coupled climate model experiments to identify the influence of atmospheric physics [Community Atmosphere Model, versions 4 and 5 (CAM4; CAM5)] and ocean model complexity (slab ocean, full-depth ocean) on the equilibrium Arctic climate response to an instantaneous CO2 doubling. In slab ocean model (SOM) experiments using CAM4 and CAM5, local radiative feedbacks, not atmospheric heat flux convergence, are the dominant control on the Arctic surface response to increased greenhouse gas forcing. Equilibrium Arctic surface air temperature warming and amplification are greater in the CAM5 SOM experiment than in the equivalent CAM4 SOM experiment. Larger 2 × CO2 radiative forcing, more positive Arctic surface albedo feedbacks, and less negative Arctic shortwave cloud feedbacks all contribute to greater Arctic surface warming and sea ice loss in CAM5 as compared to CAM4. When CAM4 is coupled to an active full-depth ocean model, Arctic Ocean horizontal heat flux convergence increases in response to the instantaneous CO2 doubling. Though this increased ocean northward heat transport slightly enhances Arctic sea ice extent loss, the representation of atmospheric processes (CAM4 versus CAM5) has a larger influence on the equilibrium Arctic surface climate response than the degree of ocean coupling (slab ocean versus full-depth ocean). These findings underscore that local feedbacks can be more important than northward heat transport for explaining the equilibrium Arctic surface climate response and response differences in coupled climate models. That said, the processes explaining the equilibrium climate response differences here may be different than the processes explaining intermodel spread in transient climate projections.

Comparisons of atmosphere–ocean simulations of greenhouse gas-induced climate change for pre-industrial and hypothetical ‘no-anthropogenic’ radiative forcing, relative to present day

The Holocene ◽  
2011 ◽  
Vol 21 (5) ◽  
pp. 793-801 ◽  
Author(s):  
J.E. Kutzbach ◽  
S.J. Vavrus ◽  
W.F. Ruddiman ◽  
G. Philippon-Berthier
Keyword(s):  
Climate Change ◽  
Sea Ice ◽  
Greenhouse Gas ◽  
Ocean Circulation ◽  
Radiative Forcing ◽  
Deep Ocean ◽  
Lower Surface ◽  
Atmospheric Model ◽  
Ocean Model ◽  
Slab Ocean

We compare climate simulations for Present-Day (PD), Pre-Industrial (PI) time, and a hypothetical (inferred) state termed No-Anthropogenic (NA) based upon the low greenhouse gas (GHG) levels of the late stages of previous interglacials that are comparable in time (orbital configuration) to the present interglacial. We use a fully coupled dynamical atmosphere–ocean model, the CCSM3. We find a consistent trend toward colder climate (lower surface temperature, more snow and sea-ice cover, lower ocean temperature, and modified ocean circulation) as the net change in GHG radiative forcing trends more negative from PD to PI to NA. The climatic response of these variables becomes larger relative to the changed GHG forcing for each step toward a colder climate state (PD to PI to NA). This amplification is significantly enhanced using the dynamical atmosphere–ocean model compared with our previous results with an atmosphere–slab ocean model, a result that conforms to earlier idealized GHG forcing experiments. However, in our case this amplification is not an idealized result, but instead helps frame important questions concerning aspects of Holocene climate change. This enhanced amplification effect leads to an increase in our estimate of the climate’s response to inferred early anthropogenic CO2 increases (NA to PI) relative to the response to industrial-era CO2 increases (PI to PD). Although observations of the climate for the hypothetical NA (inferred from observations of previous interglacials) and for PI have significant uncertainties, our new results using CCSM3 are in better agreement with these observations than our previous results from an atmospheric model coupled to a static slab ocean. The results support more strongly inferences by Ruddiman concerning indirect effects of ocean solubility/sea-ice/deep ocean ventilation feedbacks that may have contributed to a further increase in late-Holocene atmospheric CO2 beyond that caused by early anthropogenic emissions alone.

Atmospheric and Oceanic Contributions to Irreducible Forecast Uncertainty of Arctic Surface Climate

2015 ◽  
Vol 29 (1) ◽  
pp. 331-346 ◽  
Author(s):  
Steffen Tietsche ◽  
Ed Hawkins ◽  
Jonathan J. Day
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Time Scales ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Initial State ◽  
Forecast Uncertainty ◽  
Surface Climate ◽  
Oceanic Heat Flux ◽  
Arctic Surface

Abstract Uncertainty of Arctic seasonal to interannual predictions arising from model errors and initial state uncertainty has been widely discussed in the literature, whereas the irreducible forecast uncertainty (IFU) arising from the chaoticity of the climate system has received less attention. However, IFU provides important insights into the mechanisms through which predictability is lost and hence can inform prioritization of model development and observations deployment. Here, the authors characterize how internal oceanic and surface atmospheric heat fluxes contribute to the IFU of Arctic sea ice and upper-ocean heat content in an Earth system model by analyzing a set of idealized ensemble prediction experiments. It is found that atmospheric and oceanic heat flux are often equally important for driving unpredictable Arctic-wide changes in sea ice and surface water temperatures and hence contribute equally to IFU. Atmospheric surface heat flux tends to dominate Arctic-wide changes for lead times of up to a year, whereas oceanic heat flux tends to dominate regionally and on interannual time scales. There is in general a strong negative covariance between surface heat flux and ocean vertical heat flux at depth, and anomalies of lateral ocean heat transport are wind driven, which suggests that the unpredictable oceanic heat flux variability is mainly forced by the atmosphere. These results are qualitatively robust across different initial states, but substantial variations in the amplitude of IFU exist. It is concluded that both atmospheric variability and the initial state of the upper ocean are key ingredients for predictions of Arctic surface climate on seasonal to interannual time scales.

scholarly journals Climate Sensitivity of the Community Climate System Model, Version 4

2012 ◽  
Vol 25 (9) ◽  
pp. 3053-3070 ◽  
Author(s):  
C. M. Bitz ◽  
K. M. Shell ◽  
P. R. Gent ◽  
D. A. Bailey ◽  
G. Danabasoglu ◽  
...  
Keyword(s):  
Sea Ice ◽  
Climate Sensitivity ◽  
Ocean Model ◽  
System Model ◽  
Climate Response ◽  
Climate System Model ◽  
Equilibrium Climate Sensitivity ◽  
Model Version ◽  
Slab Ocean ◽  
Global Mean

Equilibrium climate sensitivity of the Community Climate System Model, version 4 (CCSM4) is 3.20°C for 1° horizontal resolution in each component. This is about a half degree Celsius higher than in the previous version (CCSM3). The transient climate sensitivity of CCSM4 at 1° resolution is 1.72°C, which is about 0.2°C higher than in CCSM3. These higher climate sensitivities in CCSM4 cannot be explained by the change to a preindustrial baseline climate. This study uses the radiative kernel technique to show that, from CCSM3 to CCSM4, the global mean lapse-rate feedback declines in magnitude and the shortwave cloud feedback increases. These two warming effects are partially canceled by cooling because of slight decreases in the global mean water vapor feedback and longwave cloud feedback from CCSM3 to CCSM4. A new formulation of the mixed layer, slab-ocean model in CCSM4 attempts to reproduce the SST and sea ice climatology from an integration with a full-depth ocean, and it is integrated with a dynamic sea ice model. These new features allow an isolation of the influence of ocean dynamical changes on the climate response when comparing integrations with the slab ocean and full-depth ocean. The transient climate response of the full-depth ocean version is 0.54 of the equilibrium climate sensitivity when estimated with the new slab-ocean model version for both CCSM3 and CCSM4. The authors argue the ratio is the same in both versions because they have about the same zonal mean pattern of change in ocean surface heat flux, which broadly resembles the zonal mean pattern of net feedback strength.

scholarly journals Model resolution influence on simulated sea ice decline

2008 ◽  
Vol 2 (5) ◽  
pp. 759-776 ◽  
Author(s):  
J. O. Sewall
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
Coupled Model ◽  
Ocean Model ◽  
Arctic Sea Ice ◽  
Model Resolution ◽  
Ocean Heat Transport ◽  
Sea Ice Decline ◽  
Arctic Sea ◽  
Model Predictions

Abstract. Satellite observations and model predictions of recent and future Arctic sea ice decline have raised concerns over the timing and potential impacts of a seasonally ice-free Arctic Ocean. Model predictions of seasonally ice-free Arctic conditions are, however, highly variable. Here I present results from fourteen climate system models from the World Climate Research Programme's (WCRP's) Coupled Model Intercomparison Project phase 3 (CMIP3) multi-model dataset that indicate modeled Arctic sea ice sensitivity to increased atmospheric CO2 forcing is strongly correlated with ice/ocean model horizontal resolution. Based on coupled model analyses and ice only simulations with the Los Alamos National Lab sea ice model (CICE), the correlation between declining Arctic sea ice cover and ice/ocean model resolution appears to depend largely on ocean model resolution and its influence on ocean heat transport into the Arctic basin. The correlation between model resolution, northward ocean heat transport, and the degree of Arctic ice loss is independent of ice model physics and complexity. This not only illustrates one difficulty in using numerical models to accurately predict the timing and magnitude of Arctic sea ice decline under increasing atmospheric greenhouse gas forcing, but also highlights one area where improved simulation (of northward ocean heat transport) could greatly decrease the uncertainties associated with predictions of future Arctic sea ice cover.

scholarly journals Rate Determining Processes of Sea Ice Growth

1985 ◽  
Vol 6 ◽  
pp. 168-170 ◽  
Author(s):  
T. Kuroda
Keyword(s):  
Heat Flux ◽  
Growth Rate ◽  
Heat Conduction ◽  
Sea Ice ◽  
Heat Transport ◽  
Environmental Conditions ◽  
Sensible Heat ◽  
Analytical Expression ◽  
Salt Diffusion

We have derived an analytical expression for the growth rate of sea ice by taking account of the processes relevant to the growth, eg heat conduction, diffusion of salt molecules, radiation, sensible heat transport, evaporation and so on. We discuss the role of each process as rate determining processes under various environmental conditions. It is shown that because of coupling of salt diffusion and heat conduction, the growth rate feeds back to the heat flux Qw from water to ice which controls the growth rate and that Qw decreases with the thickness I of sea ice, even if the environmental conditions are kept constant.

Quantifying the Influence of Atlantic Heat on Barents Sea Ice Variability and Retreat*

2012 ◽  
Vol 25 (13) ◽  
pp. 4736-4743 ◽  
Author(s):  
M. Årthun ◽  
T. Eldevik ◽  
L. H. Smedsrud ◽  
Ø. Skagseth ◽  
R. B. Ingvaldsen
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
Barents Sea ◽  
Heat Budget ◽  
Heat Content ◽  
Ocean Model ◽  
Sea Ice Extent ◽  
The Barents Sea ◽  
Ice Retreat ◽  
Sea Ice Retreat

Abstract The recent Arctic winter sea ice retreat is most pronounced in the Barents Sea. Using available observations of the Atlantic inflow to the Barents Sea and results from a regional ice–ocean model the authors assess and quantify the role of inflowing heat anomalies on sea ice variability. The interannual variability and longer-term decrease in sea ice area reflect the variability of the Atlantic inflow, both in observations and model simulations. During the last decade (1998–2008) the reduction in annual (July–June) sea ice area was 218 × 103 km2, or close to 50%. This reduction has occurred concurrent with an increase in observed Atlantic heat transport due to both strengthening and warming of the inflow. Modeled interannual variations in sea ice area between 1948 and 2007 are associated with anomalous heat transport (r = −0.63) with a 70 × 103 km2 decrease per 10 TW input of heat. Based on the simulated ocean heat budget it is found that the heat transport into the western Barents Sea sets the boundary of the ice-free Atlantic domain and, hence, the sea ice extent. The regional heat content and heat loss to the atmosphere scale with the area of open ocean as a consequence. Recent sea ice loss is thus largely caused by an increasing “Atlantification” of the Barents Sea.

scholarly journals The Role of Ocean Heat Transport in the Global Climate Response to Projected Arctic Sea Ice Loss

2016 ◽  
Vol 29 (19) ◽  
pp. 6841-6859 ◽  
Author(s):  
Robert A. Tomas ◽  
Clara Deser ◽  
Lantao Sun
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
Global Climate ◽  
Arctic Sea Ice ◽  
Climate System ◽  
Climate Response ◽  
Ocean Heat Transport ◽  
Dynamic Coupling ◽  
Arctic Sea ◽  
Arctic Sea Ice Loss

Abstract The purpose of this study is to elucidate the individual and combined roles of thermodynamic and dynamic ocean–atmosphere coupling in the equilibrium global climate response to projected Arctic sea ice loss using a suite of experiments conducted with Community Climate System Model, version 4, at 1° latitude–longitude spatial resolution. The results highlight the contrasting spatial structures and partially compensating effects of thermodynamic and dynamic coupling. In combination, thermodynamic and dynamic coupling produce a response pattern that is largely symmetric about the equator, whereas thermodynamic coupling alone yields an antisymmetric response. The latter is characterized by an interhemispheric sea surface temperature (SST) gradient, with maximum warming at high northern latitudes decreasing toward the equator, which displaces the intertropical convergence zone (ITCZ) and Hadley circulation northward. In contrast, the fully coupled response shows enhanced warming at high latitudes of both hemispheres and along the equator; the equatorial warming is driven by anomalous ocean heat transport convergence and is accompanied by a narrow equatorward intensification of the northern and southern branches of the ITCZ. In both cases, the tropical precipitation response to Arctic sea ice loss feeds back onto the atmospheric circulation at midlatitudes via Rossby wave dynamics, highlighting the global interconnectivity of the coupled climate system. This study demonstrates the importance of ocean dynamics in mediating the equilibrium global climate response to Arctic sea ice loss.

scholarly journals Convection Parameterization, Tropical Pacific Double ITCZ, and Upper-Ocean Biases in the NCAR CCSM3. Part II: Coupled Feedback and the Role of Ocean Heat Transport

2010 ◽  
Vol 23 (3) ◽  
pp. 800-812 ◽  
Author(s):  
Guang J. Zhang ◽  
Xiaoliang Song
Keyword(s):  
Surface Energy ◽  
Heat Transport ◽  
Energy Flux ◽  
Ocean Model ◽  
Tropical Pacific ◽  
Ocean Heat Transport ◽  
Surface Energy Flux ◽  
Double Itcz ◽  
Slab Ocean

Abstract This study investigates the coupled atmosphere–ocean feedback and the role of ocean dynamic heat transport in the formation of double ITCZ over the tropical Pacific in the NCAR Community Climate System Model, version 3 (CCSM3) and its alleviation when a revised Zhang–McFarlane (ZM) convection scheme is used. A hierarchy of coupling strategy is employed for this purpose. A slab ocean model is coupled with the atmospheric component of the Community Atmosphere Model, version 3 (CAM3) to investigate the local feedback between the atmosphere and the ocean. It is shown that the net surface energy flux differences in the southern ITCZ region between the revised and original ZM scheme seen in the stand-alone CAM3 simulations can cool the SST by up to 1.5°C. However, the simulated SST distribution is very sensitive to the prescribed ocean heat transport required in the slab ocean model. To understand the role of ocean heat transport, the fully coupled CCSM3 model is used. The analysis of CCSM3 simulations shows that the altered ocean dynamic heat transport when the revised ZM scheme is used is largely responsible for the reduction of SST bias in the southern ITCZ region, although surface energy flux also helps to cool the SST in the first few months of the year in seasonal variation. The results, together with those from Part I, suggest that the unrealistic simulation of convection over the southern ITCZ region in the standard CCSM3 leads to the double-ITCZ bias through complex coupled interactions between atmospheric convection, surface winds, latent heat flux, cloud radiative forcing, SST, and upper-ocean circulations. The mitigation of the double-ITCZ bias using the revised ZM scheme is achieved by altering this chain of interactions.

Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions

2007 ◽  
Vol 20 (11) ◽  
pp. 2515-2529 ◽  
Author(s):  
Jinlun Zhang
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Ocean Model ◽  
Satellite Observations ◽  
Upper Ocean ◽  
Sea Ice Extent ◽  
Salt Rejection ◽  
Ice Growth ◽  
Antarctic Sea Ice ◽  
Downward Longwave Radiation

Abstract Estimates of sea ice extent based on satellite observations show an increasing Antarctic sea ice cover from 1979 to 2004 even though in situ observations show a prevailing warming trend in both the atmosphere and the ocean. This riddle is explored here using a global multicategory thickness and enthalpy distribution sea ice model coupled to an ocean model. Forced by the NCEP–NCAR reanalysis data, the model simulates an increase of 0.20 × 1012 m3 yr−1 (1.0% yr−1) in total Antarctic sea ice volume and 0.084 × 1012 m2 yr−1 (0.6% yr−1) in sea ice extent from 1979 to 2004 when the satellite observations show an increase of 0.027 × 1012 m2 yr−1 (0.2% yr−1) in sea ice extent during the same period. The model shows that an increase in surface air temperature and downward longwave radiation results in an increase in the upper-ocean temperature and a decrease in sea ice growth, leading to a decrease in salt rejection from ice, in the upper-ocean salinity, and in the upper-ocean density. The reduced salt rejection and upper-ocean density and the enhanced thermohaline stratification tend to suppress convective overturning, leading to a decrease in the upward ocean heat transport and the ocean heat flux available to melt sea ice. The ice melting from ocean heat flux decreases faster than the ice growth does in the weakly stratified Southern Ocean, leading to an increase in the net ice production and hence an increase in ice mass. This mechanism is the main reason why the Antarctic sea ice has increased in spite of warming conditions both above and below during the period 1979–2004 and the extended period 1948–2004.

scholarly journals Drivers for Atlantic-origin waters abutting Greenland

2020 ◽  
Vol 14 (8) ◽  
pp. 2729-2753
Author(s):  
Laura C. Gillard ◽  
Xianmin Hu ◽  
Paul G. Myers ◽  
Mads Hvid Ribergaard ◽  
Craig M. Lee
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Geographic Location ◽  
Greenland Ice Sheet ◽  
Ocean Model ◽  
Warm Water ◽  
Regional Variability ◽  
Baffin Bay ◽  
Model Experiments ◽  
Atmospheric Phenomena

Abstract. The oceanic heat available in Greenland’s troughs is dependent on the geographic location of the trough, the water origin, and how the water is impacted by local processes along the pathway to the trough. This study investigates the spatial pattern and quantity of the warm water (with a temperature greater −1.5 ∘C) brought to the shelf and into the troughs abutting the Greenland Ice Sheet (GrIS). An increase in ocean heat in these troughs may drive a retreat of the GrIS. Warm water that is exchanged from the trough into the fjord may influence the melt on the marine-terminating glaciers. Several regional ocean model experiments were used to study regional differences in heat transport through troughs. Results showed that warm water extends north into Baffin Bay, reaching as far north as the Melville Bay troughs. Melville Bay troughs experienced warming following 2009. From 2004 to 2006, model experiments captured an increase in onshore heat flux in the Disko Bay trough, coinciding with the timing of the disintegration of Jakobshavn Isbrae's floating tongue and observed ocean heat increase in Disko Bay. The seasonality of the maximum onshore heat flux differs due to distance away from the Irminger Sea. Ocean temperatures near the northwestern coast and southeastern coast respond differently to changes in meltwater from Greenland and high-frequency atmospheric phenomena. With a doubling of the GrIS meltwater, Baffin Bay troughs transported ∼20 % more heat towards the coast. Fewer storms resulted in a doubling of onshore heat through Helheim Glacier's trough. These results demonstrate the regional variability of onshore heat transport through troughs and its potential implications to the GrIS.

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