Reply to “Comments on ‘Current GCMs' Unrealistic Negative Feedback in the Arctic'”

2013 ◽  
Vol 26 (19) ◽  
pp. 7789-7792
Author(s):  
Julien Boé ◽  
Alex Hall ◽  
Xin Qu
Keyword(s):  
Negative Feedback ◽  
Current Understanding ◽  
Lapse Rate ◽  
The Arctic ◽  
Rate Feedback

Abstract Pithan and Mauritsen argue that the 2009 results of Boé et al. are not consistent with current understanding of the lapse-rate feedback in the Arctic. They also argue that these results arise to an important extent from self-correlation issues. In this response, the authors argue that their results are not inconsistent with current understanding of lapse-rate feedback and demonstrate that the conclusions remain unchanged when all possibilities of self-correlation are excluded.

The Arctic lapse rate feedback: An energy budget analysis of CMIP6 models

2021 ◽  
Author(s):  
Olivia Linke ◽  
Johannes Quaas
Keyword(s):  
Arctic Ocean ◽  
Energy Budget ◽  
Surface Albedo ◽  
Heat Fluxes ◽  
Lapse Rate ◽  
The Arctic ◽  
Albedo Feedback ◽  
Temperature Lapse Rate ◽  
Atmospheric Energy ◽  
Rate Feedback

<p>The strong warming trend in the Arctic is mostly confined at the surface, and particularly evident during the cold season. The lapse rate feedback (LRF) stands out as one of the dominant causes of the Arctic amplification (besides the surface albedo feedback) given its differing response between high and lower latitudes. The LRF is the deviation from the uniform temperature change throughout the troposphere, and can thereby be quantified as the difference of tropospheric warming and surface warming. In the Arctic, it enforces a positive radiative feedback as the bottom-heavy warming is increasingly muted at higher altitudes, which has been suggested to relate to the lack of vertical mixing. In fact, climate model studies have recently identified more negative lapse rates for models with stronger inversions over large parts of the Arctic ocean, and snow-free land during winter.</p><p>Here we quantify individual components of the atmospheric energy balance to better understand the determination of the temperature lapse rate in the Arctic, which does not only interact with the surface albedo feedback, but also changes in atmospheric transport. A decomposition of the atmospheric energy budget is derived from the 6th phase of the Coupled Model Intercomparison Project (CMIP6), and concerns the radiation budgets, the transport divergence of heat and moisture, and the surface turbulent heat fluxes. Alterations of the budget components are obtained through pairs of model scenarios to simulate the impact of increasing atmospheric CO2 levels in an idealized setup.</p><p>The most notable features are the strongly opposing winter changes of the surface heat fluxes over regions of sea ice retreat and open Arctic ocean, and the interplay with the compensating energy transport divergence which can be linked to the near-surface air moist static energy in an energetic-diffusive perspective. We further aim to relate the changes of individual energetics to the temperature lapse rate in the Arctic to better understand and quantify the factors contributing to its evolution.</p>

scholarly journals Comments on “Current GCMs' Unrealistic Negative Feedback in the Arctic”

2013 ◽  
Vol 26 (19) ◽  
pp. 7783-7788 ◽  
Author(s):  
Felix Pithan ◽  
Thorsten Mauritsen
Keyword(s):  
Permutation Test ◽  
Coupled Model ◽  
Lapse Rate ◽  
The Arctic ◽  
Model Ensemble ◽  
Cmip3 Model ◽  
Rate Feedback ◽  
Intercomparison Project ◽  
Arctic Temperature ◽  
Temperature Inversions

Abstract In contrast to prior studies showing a positive lapse-rate feedback associated with the Arctic inversion, Boé et al. reported that strong present-day Arctic temperature inversions are associated with stronger negative longwave feedbacks and thus reduced Arctic amplification in the model ensemble from phase 3 of the Coupled Model Intercomparison Project (CMIP3). A permutation test reveals that the relation between longwave feedbacks and inversion strength is an artifact of statistical self-correlation and that shortwave feedbacks have a stronger correlation with intermodel spread. The present comment concludes that the conventional understanding of a positive lapse-rate feedback associated with the Arctic inversion is consistent with the CMIP3 model ensemble.

scholarly journals Polar Amplification in CCSM4: Contributions from the Lapse Rate and Surface Albedo Feedbacks

2014 ◽  
Vol 27 (12) ◽  
pp. 4433-4450 ◽  
Author(s):  
Rune G. Graversen ◽  
Peter L. Langen ◽  
Thorsten Mauritsen
Keyword(s):  
Radiative Forcing ◽  
Surface Albedo ◽  
Temperature Response ◽  
Global Scale ◽  
Lapse Rate ◽  
The Arctic ◽  
High Latitudes ◽  
Climate System Model ◽  
Polar Amplification ◽  
Rate Feedback

Abstract A vertically nonuniform warming of the troposphere yields a lapse rate feedback by altering the infrared irradiance to space relative to that of a vertically uniform tropospheric warming. The lapse rate feedback is negative at low latitudes, as a result of moist convective processes, and positive at high latitudes, due to stable stratification conditions that effectively trap warming near the surface. It is shown that this feedback pattern leads to polar amplification of the temperature response induced by a radiative forcing. The results are obtained by suppressing the lapse rate feedback in the Community Climate System Model, version 4 (CCSM4). The lapse rate feedback accounts for 15% of the Arctic amplification and 20% of the amplification in the Antarctic region. The fraction of the amplification that can be attributed to the surface albedo feedback, associated with melting of snow and ice, is 40% in the Arctic and 65% in Antarctica. It is further found that the surface albedo and lapse rate feedbacks interact considerably at high latitudes to the extent that they cannot be considered independent feedback mechanisms at the global scale.

scholarly journals Atmospheric Eddies Mediate Lapse Rate Feedback and Arctic Amplification

2017 ◽  
Vol 30 (22) ◽  
pp. 9213-9224 ◽  
Author(s):  
Nicole Feldl ◽  
Bruce T. Anderson ◽  
Simona Bordoni
Keyword(s):  
Energy Flux ◽  
High Latitude ◽  
Large Scale ◽  
Lapse Rate ◽  
The Arctic ◽  
Energy Fluxes ◽  
Latent Energy ◽  
Polar Amplification ◽  
Rate Feedback ◽  
Wide Range

Projections of amplified climate change in the Arctic are attributed to positive feedbacks associated with the retreat of sea ice and changes in the lapse rate of the polar atmosphere. Here, a set of idealized aquaplanet experiments are performed to understand the coupling between high-latitude feedbacks, polar amplification, and the large-scale atmospheric circulation. Results are compared to CMIP5. Simulated climate responses are characterized by a wide range of polar amplification (from none to nearly 15-K warming, relative to the low latitudes) under CO2 quadrupling. Notably, the high-latitude lapse rate feedback varies in sign among the experiments. The aquaplanet simulation with the greatest polar amplification, representing a transition from perennial to ice-free conditions, exhibits a marked decrease in dry static energy flux by transient eddies. Partly compensating for the reduced poleward energy flux is a contraction of the Ferrel cell and an increase in latent energy flux. Enhanced eddy energy flux is consistent with the upper-tropospheric warming that occurs in all experiments and provides a remote influence on the polar lapse rate feedback. The main conclusions are that (i) given a large, localized change in meridional surface temperature gradient, the midlatitude circulation exhibits strong compensation between changes in dry and latent energy fluxes, and (ii) atmospheric eddies mediate the nonlinear interaction between surface albedo and lapse rate feedbacks, rendering the high-latitude lapse rate feedback less positive than it would be otherwise. Consequently, the variability of the circulation response, and particularly the partitioning of energy fluxes, offers insights into understanding the magnitude of polar amplification.

Arctic winter warming due to cloud feedbacks in warm climates

2021 ◽  
Author(s):  
Eli Tziperman
Keyword(s):  
General Circulation ◽  
Lapse Rate ◽  
Arctic Climate ◽  
The Arctic ◽  
Climate Change Scenarios ◽  
Low Clouds ◽  
Rate Feedback ◽  
Extreme Cold ◽  
Arctic Climate Change ◽  
Warm Climates

<p>The climate of the Cretaceous and Eocene (146-34 Million years ago) was exceptionally warm. Crocodiles and Palm trees, which cannot withstand a few nights of subfreezing temperatures, could be found in the waters of Greenland and in the middle of present day Canada, where current winter temperatures can drop to -40C. State-of-the-art climate general circulation models cannot reproduce the exceptionally warm continental winter temperature during these periods even with very high atmospheric CO2 concentrations. One wonders whether these models are missing some significant feedback that may also affect their future global warming projections. We present two cloud feedbacks that may have contributed to such past warming, and that are found to be part of the atmospheric response to future warm climate projections, explaining the lapse-rate feedback in future Arctic climate change scenarios and the projected appearance of tropical-like deep convection during winter in the Arctic.</p><p>Recent studies (Cronin and Tziperman 2015; Cronin, Li and Tziperman, 2017), using Lagrangian single column atmospheric models, have proposed that in warmer climates low clouds would form as maritime air masses advect into Northern Hemisphere high-latitude continental interiors during winter (DJF). The greenhouse effect due to these low clouds could reduce surface radiative cooling and suppress Arctic air formation events, explaining the warm winter high-latitude continental interiors during past warm climates, and the positive lapse-rate feedback in future Arctic climate change scenarios. A 3D atmospheric general circulation model (Hu, Cronin and Tziperman, 2018) confirms these finding by simulating different warming scenarios under prescribed CO2 and sea surface temperature (SST) conditions. Winter 2-meter temperatures on extreme cold days is found to increase about 50\% faster than the winter mean temperatures and the prescribed SST. Low cloud fraction and surface longwave (LW) cloud radiative forcing also increase in both the winter mean state and on extreme cold days, consistent with the Lagrangian air-mass studies.</p><p>Air parcels experiencing extreme cold events in the present climate often arrive from Siberia and pass over the Arctic. An ice-free Arctic (during past of future warm climates) allows air parcels can accumulate moisture and therefore experience the formation of low clouds and thus the suppression of Arctic air formation. An ice free Arctic may be triggered due to the convective cloud feedback of (Abbot and Tziperman 2008, 2009; Abbot et al. 2009; Arnold et al. 2014) in which tropical-like deep atmospheric convection is triggered at high-latitudes during winter time. The radiative effects of the high tropospheric clouds associated with the atmospheric convection act to keep the surface warm, and this in turn maintains the convection active. Finally, it will be shown that the proposed cloud feedback is at work also in effectively all models run under the extended RCP 8.5 scenario, and that this may aid in the elimination of both summer and winter sea ice from the Arctic in these simulations, acting together with other related Arctic feedbacks (Hankel and Tziperman 2021, submitted).</p><p>References: https://www.seas.harvard.edu/climate/eli/reprints/</p><p> </p>

scholarly journals Sea ice and atmospheric circulation shape the high-latitude lapse rate feedback

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Nicole Feldl ◽  
Stephen Po-Chedley ◽  
Hansi K. A. Singh ◽  
Stephanie Hay ◽  
Paul J. Kushner
Keyword(s):  
Sea Ice ◽  
High Latitude ◽  
Energy Transport ◽  
Lower Troposphere ◽  
Longwave Radiation ◽  
Lapse Rate ◽  
Arctic Amplification ◽  
Albedo Feedback ◽  
Rate Feedback ◽  
Isentropic Surface

Abstract Arctic amplification of anthropogenic climate change is widely attributed to the sea-ice albedo feedback, with its attendant increase in absorbed solar radiation, and to the effect of the vertical structure of atmospheric warming on Earth’s outgoing longwave radiation. The latter lapse rate feedback is subject, at high latitudes, to a myriad of local and remote influences whose relative contributions remain unquantified. The distinct controls on the high-latitude lapse rate feedback are here partitioned into “upper” and “lower” contributions originating above and below a characteristic climatological isentropic surface that separates the high-latitude lower troposphere from the rest of the atmosphere. This decomposition clarifies how the positive high-latitude lapse rate feedback over polar oceans arises primarily as an atmospheric response to local sea ice loss and is reduced in subpolar latitudes by an increase in poleward atmospheric energy transport. The separation of the locally driven component of the high-latitude lapse rate feedback further reveals how it and the sea-ice albedo feedback together dominate Arctic amplification as a coupled mechanism operating across the seasonal cycle.

Lapse Rate Peculiarities in the Arctic from Reanalysis Data and Model Simulations

2019 ◽  
Vol 44 (2) ◽  
pp. 97-102 ◽  
Author(s):  
M. G. Akperov ◽  
I. I. Mokhov ◽  
M. A. Dembitskaya ◽  
M. R. Parfenova ◽  
A. Rinke
Keyword(s):  
Reanalysis Data ◽  
Lapse Rate ◽  
The Arctic ◽  
Model Simulations

scholarly journals Estimates of vertical eddy diffusivity in the upper mesosphere in the presence of a mesospheric inversion layer

2011 ◽  
Vol 29 (11) ◽  
pp. 2019-2029 ◽  
Author(s):  
R. L. Collins ◽  
G. A. Lehmacher ◽  
M. F. Larsen ◽  
K. Mizutani
Keyword(s):  
Diffusion Coefficient ◽  
Inversion Layer ◽  
Eddy Diffusion ◽  
Lapse Rate ◽  
The Arctic ◽  
Maximum Temperature ◽  
Lower Edge ◽  
Sodium Layer ◽  
Eddy Diffusion Coefficient ◽  
Lidar Observations

Abstract. Rayleigh and resonance lidar observations were made during the Turbopause experiment at Poker Flat Research Range, Chatanika Alaska (65° N, 147° W) over a 10 h period on the night of 17–18 February 2009. The lidar observations revealed the presence of a strong mesospheric inversion layer (MIL) at 74 km that formed during the observations and was present for over 6 h. The MIL had a maximum temperature of 251 K, amplitude of 27 ± 7 K, a depth of 3.0 km, and overlying lapse rate of 9.4 ± 0.3 K km−1. The MIL was located at the lower edge of the mesospheric sodium layer. During this coincidence the lower edge of the sodium layer was lowered by 2 km to 74 km and the bottomside scale height of the sodium increased from 1 km to 15 km. The structure of the MIL and sodium are analyzed in terms of vertical diffusive transport. The analysis yields a lower bound for the eddy diffusion coefficient of 430 m2 s−1 and the energy dissipation rate of 2.2 mW kg−1 at 76–77 km. This value of the eddy diffusion coefficient, determined from naturally occurring variations in mesospheric temperatures and the sodium layer, is significantly larger than those reported for mean winter values in the Arctic but similar to individual values reported in regions of convective instability by other techniques.

scholarly journals Arctic hydroclimate variability during the last 2000 years – current understanding and research challenges

2017 ◽  
Author(s):  
Hans W. Linderholm ◽  
Marie Nicolle ◽  
Pierre Francus ◽  
Konrad Gajewski ◽  
Samuli Helama ◽  
...  
Keyword(s):  
North America ◽  
Climate Models ◽  
Reanalysis Data ◽  
Current Understanding ◽  
Ice Age ◽  
The Arctic ◽  
Oceanic Circulation ◽  
Natural Ecosystems ◽  
Temperature And Precipitation ◽  
Hydroclimate Variability

Abstract. Along with Arctic amplification, changes in Arctic hydroclimate have become increasingly apparent. Reanalysis data show increasing trends in Arctic temperature and precipitation over the 20th century, but changes are not homogenous across seasons or space. The observed hydroclimate changes are expected to continue, and possibly accelerate, in the coming century, not only affecting pan-Arctic natural ecosystems and human activities, but also lower latitudes through changes in atmospheric and oceanic circulation. However, a lack of spatiotemporal observational data makes reliable quantification of Arctic hydroclimate change difficult, especially in a long-term context. To understand hydroclimate variability and the mechanisms driving observed changes, beyond the instrumental record, climate proxies are needed. Here we bring together the current understanding of Arctic hydroclimate during the past 2000 years, as inferred from natural archives and proxies and palaeoclimate model simulations. Inadequate proxy data coverage is apparent, with distinct data gaps in most of Eurasia and parts of North America, which makes robust assessments for the whole Arctic currently impossible. Hydroclimate proxies and climate models indicate that the Medieval Climate Anomaly (MCA) was anomalously wet, while conditions were in general drier during the Little Ice Age (LIA), relative to the last 2000 years. However, it is clear that there are large regional differences, which are especially evident during the LIA. Due to the spatiotemporal differences in Arctic hydroclimate, we recommend detailed regional studies, e.g. including field reconstructions, to disentangle spatial patterns and potential forcing factors. At present, it is only possible to carry out regional syntheses for a few areas of the Arctic, e.g. Fennoscandia, Greenland and western North America. To fully assess pan-Arctic hydroclimate variability for the last two millennia additional proxy records are required.

scholarly journals Causes of the Arctic’s Lower-Tropospheric Warming Structure

2021 ◽  
pp. 1-52
Keyword(s):  
Climate Change ◽  
Boundary Layer ◽  
Sea Ice ◽  
Temperature Response ◽  
Lapse Rate ◽  
The Arctic ◽  
Turbulent Heat ◽  
Temperature Structure ◽  
Arctic Temperature ◽  
Temperature Inversions

Abstract Arctic amplification has been attributed predominantly to a positive lapse rate feedback in winter, when boundary-layer temperature inversions focus warming near the surface. Predicting high-latitude climate change effectively thus requires identifying the local and remote physical processes that set the Arctic’s vertical warming structure. In this study, we analyze output from the CESM Large Ensemble’s 21st century climate change projection to diagnose the relative influence of two Arctic heating sources, local sea-ice loss and remote changes in atmospheric heat transport. Causal effects are quantified with a statistical inference method, allowing us to assess the energetic pathways mediating the Arctic temperature response and the role of internal variability across the ensemble. We find that a step-increase in latent heat flux convergence causes Arctic lower-tropospheric warming in all seasons, while additionally reducing net longwave cooling at the surface. However, these effects only lead to small and short-lived changes in boundary layer inversion strength. By contrast, a step-decrease in sea-ice extent in the melt season causes, in fall and winter, surface-amplified warming and weakened boundary-layer temperature inversions. Sea-ice loss also enhances surface turbulent heat fluxes and cloud-driven condensational heating, which mediate the atmospheric temperature response. While the aggregate effect of many moist transport events and seasons of sea-ice loss will be different than the response to hypothetical perturbations, our results nonetheless highlight the mechanisms that alter the Arctic temperature inversion in response to CO2 forcing. As sea ice declines, the atmosphere’s boundary-layer temperature structure is weakened, static stability decreases, and a thermodynamic coupling emerges between the Arctic surface and the overlying troposphere.

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