Impacts of the lapse rate feedback on surface energy balance in the New Arctic
Abstract
The radiative response to non-vertically uniform warming in response to CO2 forcing is known as the lapse rate feedback (LRF). LRF has a seasonality by which it is positive in the Arctic winter, due to the highly stable conditions of the boundary layer, effectively trapping warming near the surface and reducing OLR. The LRF interacts with other feedbacks that amplify surface warming, including the ice-albedo effect, ice-insulation effect, circulation, air-sea heat exchange, and clouds, making it a key feedback to determining the Arctic surface energy balance. This study first explores how the LRF contributes to interannual variability in the surface energy budget by compositing temperature profiles from months with the largest and smallest anomalies of various climate parameters, such as downwelling longwave radiation, lower tropospheric stability, sea ice concentration, and surface turbulent fluxes. The difference between temperature profiles computed for the largest anomalies and smallest anomalies are used in surface radiative kernels to calculate the response of the LRF to changes in these surface parameters; this analysis is also carried out for observations using CERES-EBAF and MERRA-2 to investigate the role of lapse rate change on observed interannual surface energy budget variability and assess the performance of the models. Next, changes in the LRF are explored using the CMIP5 RCP8.5 simulation. Using lag/lead correlations, a feedback mechanism is proposed whereby seasonal heat exchange in ice-retreat regions contributes to a stronger LRF, facilitated by increasing summer heat storage in the ocean, increasing surface turbulent fluxes in autumn, and circulation changes that redistribute this heat to other Arctic regions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A52A..02B
- Keywords:
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- 3310 Clouds and cloud feedbacks;
- ATMOSPHERIC PROCESSES;
- 3359 Radiative processes;
- ATMOSPHERIC PROCESSES;
- 0764 Energy balance;
- CRYOSPHERE;
- 1621 Cryospheric change;
- GLOBAL CHANGE