Sensitivity of Polar Amplification to Varying Insolation Conditions

Abstract

The mechanism of polar amplification in the absence of surface albedo feedback is investigated using an atmospheric model coupled to an aquaplanet slab ocean forced by a CO2 doubling. In particular, we examine the sensitivity of polar surface warming response under different insolation conditions from equinox (EQN) to annual mean (ANN) to seasonally varying (SEA). Varying insolation greatly affects the climatological static stability. The equinox condition, with the largest polar static stability, exhibits a bottom-heavy vertical profile of polar warming response that leads to the strongest polar amplification. In contrast, the polar warming response in ANN and SEA exhibits a maximum in the midtroposphere, which leads to only weak polar amplification. The midtropospheric warming maximum, which results from an increased poleward atmospheric energy transport in response to the tropics-to-pole energy imbalance, contributes to polar surface warming via downward clear-sky longwave radiation. However, it is cancelled by negative cloud radiative feedbacks locally. Furthermore, the polar lapse rate feedback, calculated from radiative kernels, is negative due to the midtropospheric warming maximum, and hence is not able to promote the polar surface warming. On the other hand, the polar lapse rate feedback in EQN is positive due to the bottom-heavy warming response, contributing to the strong polar surface warming. This contrast suggests that locally induced positive radiative feedbacks are necessary for strong polar amplification. Our results demonstrate how interactions among climate feedbacks determine the strength of polar amplification.

Quantifying the Impact of Wind and Surface Humidity‐Induced Surface Heat Exchange on the Circulation Shift in Response to Increased CO2

“…The aquaplanet experiments with annual‐mean insolation show qualitatively similar results (black lines in Figures S5b and S7, first column in Figure S8, and black x in Figure S9), except that the polar amplification is much reduced consistent with Kim et al. (2018).…”

“…The cloud responses are different with annual‐mean insolation: The high‐latitude (poleward of 50°) low cloud is less prevalent, and its response to quadrupled CO 2 is much weaker (cf. Figure S10 with S6), due to the lack of inversion atop the high‐latitude boundary layer (Kim et al., 2018). The global mean net TOACRE response in the annual‐mean locked experiment is +1.6 W m −2 , corresponding to a global mean SST increases of +1.7 K without polar amplification (Figure S7a, blue line).…”

Neutral modes of surface temperature and the optimal ocean thermal forcing for global cooling

“…Origin of the nonlinearity How does the nonlinear cooling come about in the first place? Several sources of nonlinearity previously identified in climate system (asides from ocean dynamics) can give a cooling effect, to name a few: the nonlinear cooling effect of vertical masking of both clear-sky quantities (such as water vapor) and cloud 22 , the remnant effect of the stabilized small ice-cap instability giving rise to a greater cooling than a warming under opposite forcing perturbations 40 , the negative nonlinear cloud radiative effect at surface attached to the seasonality in the polar climate 41 , plus the nonlinear atmospheric dynamics 39,42 . An parallel investigation has been undertaken through a suite of methodically designed experiments wherein sea ice formation is disabled to form an ice-free climate (see Methods and ref.…”

A quality control approach to better characterize the spatial distribution of snow depth over New Brunswick, Canada

“…Snow cover is one of the main indicators of climate change and is mostly used in order to study the relationship between climate and cryosphere (Mudryk et al, ). In the last three decades, the polar and cold regions have experienced the most rapid warming on Earth, especially in the Northern Hemisphere (Kim et al, ). The quick increase of temperature in these regions is part of global warming, with regional amplifications due to the relationships established between land surface temperature, oceanic circulation, glacier fluctuations, snow cover extent and duration as well as atmospheric patterns (Juřicová and Fratianni (), Serreze and Barry (), Pithan and Mauritsen (), and Ballinger et al .…”

“…the most rapid warming on Earth, especially in the Northern Hemisphere (Kim et al, 2018). The quick increase of temperature in these regions is part of global warming, with regional amplifications due to the relationships established between land surface temperature, oceanic circulation, glacier fluctuations, snow cover extent and duration as well as atmospheric patterns (Juřicová and Fratianni (2018), Serreze and Barry (2011), Pithan and Mauritsen (2014), and Ballinger et al (2018) showed that Canada, such as many other northern and cold regions, experienced a rapid warming with a temperature increase of approximately 1.5 C over the 1950-2010 period and also a significant statistical decrease in the number of ice days in the 1974-2013 period .…”