Use, Smithsonian Since the 1970s, simulations of climate change forced by increased CO 2 concentrations have predicted warming that is greatest in polar regions. This strong negative correlation is expected, as a more negative Δ(RLUT âˆ’ RLDS) is consistent with greater surface-than-atmospheric warming. CCA1 - Lapse rate feedback; CCA2 - Surface processes; CCA3 - Arctic mixed-phase clouds; CCA4 - Air mass transport and transformation; Close; Close; Projects. We will go through each feedback in class. Sea ice loss plays a paramount role in establishing the spatial pattern (figure 5 ) and seasonality (figure 2 ) of Arctic warming and AA. However, lapse rate and Planck feedbacks play a larger role in climate model simulations of Arctic amplification than the surface albedo feedback (Pithan and Mauritsen, 2014). An analysis across individual models indicates a significant intermodel lapse-rate feedback spread that also depends weakly on stratification. The ice-albedo feedback plays a bigger role, but two analyses (Pithan and Mauritsen (2014) and Stuecker et al. The lapse-rate feedback radiative perturbation is defined as the difference between the TOA radiative perturbation from the total temperature change and that of a vertically uniform warming equal to the surface warming. 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. The aquaplanet simulation with the greatest polar amplification, representing a transition from perennial to ice-free conditions, exhibits strong compensation between changes in dry and latent atmospheric energy fluxes and a contraction of the Ferrel cell. Figure 4c shows a weaker than expected correlation between the lapse-rate feedback and Δ(RLUT âˆ’ RLDS) (R = âˆ’0.40, significant at 95% confidence), suggesting that differential atmospheric cooling is not as strongly tied to the domain averaged lapse-rate feedback as it is for individual grid boxes. The lapse-rate feedback shows some dependence on LTS in sea ice-retreat regions; however, this behavior is linked to ΔSIC (Figures 2e and 2f). (2011) further argue that the degree of stable stratification amplifies surface warming by producing stronger differential atmospheric cooling (increasing downward longwave radiation to the surface more than outgoing longwave radiation to space), such that stronger stable stratification leads to a greater positive lapse-rate feedback. As to how it actually works (and why it doesn't work for CO2, CH4, N2O . 2(b)), the effects of the OHU, lapse rate feedback, and CO 2 radiative forcing play a leading role in making greater winter warming—similar to the discussion in Pithan and Mauritsen (2014) from a TOA perspective in CMIP5 models, showing different relative importance between CO 2 forcing and AHT. 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. Under anthropogenic forcing, this sensitivity gives rise to the lapse-rate feedback. We find that 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. (Alternatively, if the ice thins enough then the near-surface air could be warmed by the waters beneath the ice through conduction, giving a similar effect.). The degree of stratification (Figure 4b), however, shows a weak positive correlation (R = 0.48; significant at 95% confidence) between a model's lapse-rate feedback and LTS in DJF (near-zero annual mean correlation), a slightly stronger relationship than shown in Section 3.3. Modelling and observational approaches. (2009), Kay et al. Arctic warming is caused by a number of climate feedbacks, most notably ice- albedo feedback and lapse-rate feed-back (Pithan and Mauritsen, 2014). Found inside – Page 21The Connection between the Water Vapor and Lapse-Rate Feedbacks There is some variation in the magnitude of the water ... Moreover, the observed decline in the spatial extent of Arctic sea ice at the end of the melt season between 1953 ... In the Antarctic, 20 % of the amplification can be attributed to the lapse-rate . The lapse-rate feedback is therefore negative in the tropics and positive in the Arctic. The strength of this feedback depends on the initial mean-state supercooled liquid fraction (SLF) and the ice crystal effective radii. Physics, Solar Abstract Whether sea-ice loss or lapse-rate feedback dominates the Arctic amplification remains an open question. In winter the high latitudes don’t get any insolation, so apart from some downwelling long-wave radiation from the atmosphere, there’s nothing to heat the surface. Roe et al. The lapse rate feedback, on the other hand, represents various atmo-spheric processes that affect the lapse rate differently. 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). Figures 2e and 2f illustrate the link between the lapse-rate feedback and ΔSIC for all sea ice regions. It is relatively small and . Agreement NNX16AC86A, Is ADS down? However, a firm mechanistic understanding of this feedback remains elusive. The longwave radiation (R) emitted by the Earth's surface rises with temperature (T) following RD ˙T4, where is This book, resulting from an international symposium organized by the Potsdam Institute, has 2 aims: first, to integrate contributions from leading researchers and scholars from around the world to provide a multifaceted perspective of what ... manuscript submitted to Geophysical Research Letters 2 16 Abstract 17 The lapse-rate feedback is the dominant driver of stronger warming in the Arctic than the 18 Antarctic in simulations with increased CO 2. The lapse-rate feedback is negative in the tropics and positive at high latitudes: at low . The Planck feedback is generally overlooked as a contributor to Arctic amplification, even though the underlying physics is well established21. reported that strong present-day Arctic temperature inversions are assoc. The Planck feedback comes from the fact that black bodies emit radiation as temperature to the fourth power (T4). Our results show the Arctic lapse-rate feedback as a seasonal and regional phenomenon that manifests from multiple processes and is not a single-process feedback mediated by the degree of stable stratification. a positive lapse-rate feedback in the Arctic, whereas. for both the Arctic and the Tropics Planck = Planck curvature CO2 = radiative forcing F Recent diagnostic study: What is causing Arctic amplification? The solid line bisecting each box is the median. Bintanja et al. The increased downward LW radiation decreases the positive lapse rate feedback in the Arctic, thus resulting in reduced Arctic amplification. 20 . Our results support the multiprocess perspective of the Arctic lapse-rate feedback, whereby the mechanisms responsible for the nonuniform warming profile determine the lapse-rate feedback.
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