scholarly journals Projected Changes in the Seasonal Cycle of Surface Temperature

2012 ◽  
Vol 25 (18) ◽  
pp. 6359-6374 ◽  
Author(s):  
John G. Dwyer ◽  
Michela Biasutti ◽  
Adam H. Sobel
Keyword(s):  
Heat Capacity ◽  
Sea Ice ◽  
Surface Temperature ◽  
Seasonal Cycle ◽  
Phase Delay ◽  
First Century ◽  
Effective Heat Capacity ◽  
Effective Heat ◽  
Twenty First Century ◽  
Global Mean

Abstract When forced with increasing greenhouse gases, global climate models project a delay in the phase and a reduction in the amplitude of the seasonal cycle of surface temperature, expressed as later minimum and maximum annual temperatures and greater warming in winter than in summer. Most of the global mean changes come from the high latitudes, especially over the ocean. All 24 Coupled Model Intercomparison Project phase 3 models agree on these changes and, over the twenty-first century, average a phase delay of 5 days and an amplitude decrease of 5% for the global mean ocean surface temperature. Evidence is provided that the changes are mainly driven by sea ice loss: as sea ice melts during the twenty-first century, the previously unexposed open ocean increases the effective heat capacity of the surface layer, slowing and damping the temperature response. From the tropics to the midlatitudes, changes in phase and amplitude are smaller and less spatially uniform than near the poles but are still prevalent in the models. These regions experience a small phase delay but an amplitude increase of the surface temperature cycle, a combination that is inconsistent with changes to the effective heat capacity of the system. The authors propose that changes in this region are controlled by changes in surface heat fluxes.

scholarly journals Projected Changes in Daily Variability and Seasonal Cycle of Near-Surface Air Temperature over the Globe during the Twenty-First Century

2019 ◽  
Vol 32 (24) ◽  
pp. 8537-8561 ◽  
Author(s):  
Jiao Chen ◽  
Aiguo Dai ◽  
Yaocun Zhang
Keyword(s):  
Sea Ice ◽  
Air Temperature ◽  
Seasonal Cycle ◽  
Surface Air Temperature ◽  
First Century ◽  
The Arctic ◽  
Boreal Summer ◽  
High Latitudes ◽  
Low Latitudes ◽  
Twenty First Century

Abstract Increases in atmospheric greenhouse gases will not only raise Earth’s temperature but may also change its variability and seasonal cycle. Here CMIP5 model data are analyzed to quantify these changes in surface air temperature (Tas) and investigate the underlying processes. The models capture well the mean Tas seasonal cycle and variability and their changes in reanalysis, which shows decreasing Tas seasonal amplitudes and variability over the Arctic and Southern Ocean from 1979 to 2017. Daily Tas variability and seasonal amplitude are projected to decrease in the twenty-first century at high latitudes (except for boreal summer when Tas variability increases) but increase at low latitudes. The day of the maximum or minimum Tas shows large delays over high-latitude oceans, while it changes little at low latitudes. These Tas changes at high latitudes are linked to the polar amplification of warming and sea ice loss, which cause larger warming in winter than summer due to extra heating from the ocean during the cold season. Reduced sea ice cover also decreases its ability to cause Tas variations, contributing to the decreased Tas variability at high latitudes. Over low–midlatitude oceans, larger increases in surface evaporation in winter than summer (due to strong winter winds, strengthened winter winds in the Southern Hemisphere, and increased winter surface humidity gradients over the Northern Hemisphere low latitudes), coupled with strong ocean mixing in winter, lead to smaller surface warming in winter than summer and thus increased seasonal amplitudes there. These changes result in narrower (wider) Tas distributions over the high (low) latitudes, which may have important implications for other related fields.

scholarly journals Seasonality in Arctic Warming Driven By Sea Ice Effective Heat Capacity

2021 ◽  
pp. 1-44
Keyword(s):  
Heat Capacity ◽  
Sea Ice ◽  
Seasonal Pattern ◽  
Surface Heat ◽  
Lapse Rate ◽  
Effective Surface ◽  
Effective Heat Capacity ◽  
Arctic Warming ◽  
Rate Feedback ◽  
Effective Heat

Abstract Arctic surface warming under greenhouse gas forcing peaks in winter and reaches its minimum during summer in both observations and model projections. Many mechanisms have been proposed to explain this seasonal asymmetry, but disentangling these processes remains a challenge in the interpretation of general circulation model (GCM) experiments. To isolate these mechanisms, we use an idealized single-column sea ice model (SCM) which captures the seasonal pattern of Arctic warming. SCM experiments demonstrate that as sea ice melts and exposes open ocean, the accompanying increase in effective surface heat capacity can alone produce the observed pattern of peak warming in early winter (shifting to late winter under increased forcing) by slowing the seasonal heating rate, thus delaying the phase and reducing the amplitude of the seasonal cycle of surface temperature. To investigate warming seasonality in more complex models, we perform GCM experiments that individually isolate sea-ice albedo and thermodynamic effects under CO2 forcing. These also show a key role for the effective heat capacity of sea ice in promoting seasonal asymmetry through suppressing summer warming, in addition to precluding summer climatological inversions and a positive summer lapse-rate feedback. Peak winter warming in GCM experiments is further supported by a positive winter lapse-rate feedback, due to cold initial surface temperatures and strong surface-trapped warming that are enabled by the albedo effects of sea ice alone. While many factors contribute to the seasonal pattern of Arctic warming, these results highlight changes in effective surface heat capacity as a central mechanism supporting this seasonality.

scholarly journals Toward a Seasonally Ice-Covered Arctic Ocean: Scenarios from the IPCC AR4 Model Simulations

2006 ◽  
Vol 19 (9) ◽  
pp. 1730-1747 ◽  
Author(s):  
Xiangdong Zhang ◽  
John E. Walsh
Keyword(s):  
Twentieth Century ◽  
Sea Ice ◽  
Seasonal Cycle ◽  
First Century ◽  
Multimodel Ensemble ◽  
Model Simulations ◽  
Ice Coverage ◽  
Twenty First Century ◽  
Ipcc Ar4 ◽  
Multiyear Ice

Abstract The sea ice simulations by the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) models for the climate of the twentieth century and for global warming scenarios have been synthesized. A large number of model simulations realistically captured the climatological annual mean, seasonal cycle, and temporal trends of sea ice area over the Northern Hemisphere during 1979–99, although there is considerable scatter among the models. In particular, multimodel ensemble means show promising estimates very close to observations for the late twentieth century. Model projections for the twenty-first century demonstrate the largest sea ice area decreases generally in the Special Report on Emission Scenarios (SRES) A1B and A2 scenarios compared with the B1 scenario, indicating large multimodel ensemble mean reductions of −3.54 ± 1.66 × 105 km2 decade−1 in A1B, −4.08 ± 1.33 × 105 km2 decade−1 in A2, and −2.22 ± 1.11 × 105 km2 decade−1 in B1. The corresponding percentage reductions are 31.1%, 33.4%, and 21.6% in the last 20 yr of the twenty-first century, relative to 1979–99. Furthermore, multiyear ice coverage decreases rapidly at rates of −3.86 ± 2.07 × 105 km2 decade−1 in A1B, −4.94 ± 1.91 × 105 km2 decade−1 in A2, and −2.67 ± 1.7107 × 105 km2 decade−1 in B1, making major contributions to the total ice reductions. In contrast, seasonal (first year) ice area increases by 1.10 ± 2.46 × 105 km2 decade−1, 1.99 ± 1.47 × 105 km2 decade−1, and 1.05 ± 1.9247 × 105 km2 decade−1 in the same scenarios, leading to decreases of 59.7%, 65.0%, and 45.8% of the multiyear ice area, and increases of 14.1%, 27.8%, and 11.2% of the seasonal ice area in the last 20 yr of this century. Statistical analysis shows that many of the models are consistent in the sea ice change projections among all scenarios. The results include an evaluation of the 99% confidence interval of the model-derived change of sea ice coverage, giving a quantification of uncertainties in estimating sea ice changes based on the participating models. Hence, the seasonal cycle of sea ice area is amplified and an increased large portion of seasonally ice-covered Arctic Ocean is expected at the end of the twenty-first century. The very different changes of multiyear and seasonal ice may have significant implications for the polar energy and hydrological budgets and pathways.

scholarly journals Centennial-Scale Sea Surface Temperature Analysis and Its Uncertainty

2014 ◽  
Vol 27 (1) ◽  
pp. 57-75 ◽  
Author(s):  
Shoji Hirahara ◽  
Masayoshi Ishii ◽  
Yoshikazu Fukuda
Keyword(s):  
Sea Ice ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Specific Area ◽  
Sea Surface ◽  
Sampling Errors ◽  
Sea Ice Concentration ◽  
Sst Variability ◽  
Analysis Errors ◽  
Global Mean

Abstract A new sea surface temperature (SST) analysis on a centennial time scale is presented. In this analysis, a daily SST field is constructed as a sum of a trend, interannual variations, and daily changes, using in situ SST and sea ice concentration observations. All SST values are accompanied with theory-based analysis errors as a measure of reliability. An improved equation is introduced to represent the ice–SST relationship, which is used to produce SST data from observed sea ice concentrations. Prior to the analysis, biases of individual SST measurement types are estimated for a homogenized long-term time series of global mean SST. Because metadata necessary for the bias correction are unavailable for many historical observational reports, the biases are determined so as to ensure consistency among existing SST and nighttime air temperature observations. The global mean SSTs with bias-corrected observations are in agreement with those of a previously published study, which adopted a different approach. Satellite observations are newly introduced for the purpose of reconstruction of SST variability over data-sparse regions. Moreover, uncertainty in areal means of the present and previous SST analyses is investigated using the theoretical analysis errors and estimated sampling errors. The result confirms the advantages of the present analysis, and it is helpful in understanding the reliability of SST for a specific area and time period.

scholarly journals Climate System Response to External Forcings and Climate Change Projections in CCSM4

2012 ◽  
Vol 25 (11) ◽  
pp. 3661-3683 ◽  
Author(s):  
Gerald A. Meehl ◽  
Warren M. Washington ◽  
Julie M. Arblaster ◽  
Aixue Hu ◽  
Haiyan Teng ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Sea Ice ◽  
Meridional Overturning Circulation ◽  
Climate System ◽  
First Century ◽  
The Arctic ◽  
System Response ◽  
Transient Climate Response ◽  
Climate System Model ◽  
Twenty First Century

Results are presented from experiments performed with the Community Climate System Model, version 4 (CCSM4) for the Coupled Model Intercomparison Project phase 5 (CMIP5). These include multiple ensemble members of twentieth-century climate with anthropogenic and natural forcings as well as single-forcing runs, sensitivity experiments with sulfate aerosol forcing, twenty-first-century representative concentration pathway (RCP) mitigation scenarios, and extensions for those scenarios beyond 2100–2300. Equilibrium climate sensitivity of CCSM4 is 3.20°C, and the transient climate response is 1.73°C. Global surface temperatures averaged for the last 20 years of the twenty-first century compared to the 1986–2005 reference period for six-member ensembles from CCSM4 are +0.85°, +1.64°, +2.09°, and +3.53°C for RCP2.6, RCP4.5, RCP6.0, and RCP8.5, respectively. The ocean meridional overturning circulation (MOC) in the Atlantic, which weakens during the twentieth century in the model, nearly recovers to early twentieth-century values in RCP2.6, partially recovers in RCP4.5 and RCP6, and does not recover by 2100 in RCP8.5. Heat wave intensity is projected to increase almost everywhere in CCSM4 in a future warmer climate, with the magnitude of the increase proportional to the forcing. Precipitation intensity is also projected to increase, with dry days increasing in most subtropical areas. For future climate, there is almost no summer sea ice left in the Arctic in the high RCP8.5 scenario by 2100, but in the low RCP2.6 scenario there is substantial sea ice remaining in summer at the end of the century.

Effect of Brownian Motion and External Magnetic Field on the Effective Heat Capacity of Ferrofluids

2011 ◽  
Author(s):  
Narges Susan Mousavi Kh. ◽  
Sunil Kumar ◽  
Arvind Narayanaswamy
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
Brownian Motion ◽  
Energy Equation ◽  
Volume Fraction ◽  
Physical Parameters ◽  
Effective Heat Capacity ◽  
Effective Heat ◽  
Negligible Contribution

An Eulerian formalism is used to derive the energy equation for a system of magnetic nanoparticles in a fluid (ferrofluid) in the presence of uniform magnetic field. The energy equation proposed here contains an effective heat capacity, which has contributions from: (1) Brownian motion of nanoparticles, (2) magnetic field, (3) temperature, and (4) volume fraction of particles. The modified term quantitatively shows the negligible contribution of the first three factors but the significant effect of concentration of particles in change in heat capacity of ferrofluid. In order to have a better understanding of the problem, the equation is converted to a non dimensional form from which the role of each of physical parameters can be inferred.

The Seasonal Atmospheric Response to Projected Arctic Sea Ice Loss in the Late Twenty-First Century

2010 ◽  
Vol 23 (2) ◽  
pp. 333-351 ◽  
Author(s):  
Clara Deser ◽  
Robert Tomas ◽  
Michael Alexander ◽  
David Lawrence
Keyword(s):  
Sea Ice ◽  
High Latitude ◽  
Vertical Structure ◽  
Arctic Sea Ice ◽  
First Century ◽  
The Arctic ◽  
Arctic Sea ◽  
Ice Conditions ◽  
Twenty First Century ◽  
Arctic Sea Ice Loss

Abstract The authors investigate the atmospheric response to projected Arctic sea ice loss at the end of the twenty-first century using an atmospheric general circulation model (GCM) coupled to a land surface model. The response was obtained from two 60-yr integrations: one with a repeating seasonal cycle of specified sea ice conditions for the late twentieth century (1980–99) and one with that of sea ice conditions for the late twenty-first century (2080–99). In both integrations, a repeating seasonal cycle of SSTs for 1980–99 was prescribed to isolate the impact of projected future sea ice loss. Note that greenhouse gas concentrations remained fixed at 1980–99 levels in both sets of experiments. The twentieth- and twenty-first-century sea ice (and SST) conditions were obtained from ensemble mean integrations of a coupled GCM under historical forcing and Special Report on Emissions Scenarios (SRES) A1B scenario forcing, respectively. The loss of Arctic sea ice is greatest in summer and fall, yet the response of the net surface energy budget over the Arctic Ocean is largest in winter. Air temperature and precipitation responses also maximize in winter, both over the Arctic Ocean and over the adjacent high-latitude continents. Snow depths increase over Siberia and northern Canada because of the enhanced winter precipitation. Atmospheric warming over the high-latitude continents is mainly confined to the boundary layer (below ∼850 hPa) and to regions with a strong low-level temperature inversion. Enhanced warm air advection by submonthly transient motions is the primary mechanism for the terrestrial warming. A significant large-scale atmospheric circulation response is found during winter, with a baroclinic (equivalent barotropic) vertical structure over the Arctic in November–December (January–March). This response resembles the negative phase of the North Atlantic Oscillation in February only. Comparison with the fully coupled model reveals that Arctic sea ice loss accounts for most of the seasonal, spatial, and vertical structure of the high-latitude warming response to greenhouse gas forcing at the end of the twenty-first century.

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