Abstract
Observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) project are used to describe a sequence of events linking midwinter long-range advection of atmospheric heat and moisture into the Arctic Basin, formation of supercooled liquid water clouds, enhancement of net surface energy fluxes through increased downwelling longwave radiation, and reduction in near-surface conductive heat flux loss due to a warming of the surface, thereby leading to a reduction in sea-ice bottom growth. The analyses provide details of two events during Jan. 1–12, 1998, one entering the Arctic through Fram Strait and the other from northeast Siberia; winter statistics extend the results. Both deep, precipitating frontal clouds and post-frontal stratocumulus clouds impact the surface radiation and energy budget. Cloud liquid water, occurring preferentially in stratocumulus clouds extending into the base of the inversion, provides the strongest impact on surface radiation and hence modulates the surface forcing, as found previously. The observations suggest a minimum water vapor threshold, likely case dependent, for producing liquid water clouds. Through responses to the radiative forcing and surface warming, this cloud liquid water also modulates the turbulent and conductive heat fluxes, and produces a thermal wave penetrating into the sea ice. About 20–33 % of the observed variations of bottom ice growth can be directly linked to variations in surface conductive heat flux, with retarded ice growth occurring several days after these moisture plumes reduce the surface conductive heat flux. This sequence of events modulate pack-ice wintertime environmental conditions and total ice growth, and has implications for the annual sea-ice evolution, especially for the current conditions of extensive thinner ice.
Highlights
The Arctic Ocean is a region approximately the size of the United States and whose climate is changing at a rate more rapidly than elsewhere on the globe
The primary source of the meteorological and surface energy budget (SEB) data is the Atmospheric Surface Flux Group (ASFG) data set (Persson et al 2002), while measurements from the sites run by the Surface Heat Budget of the Arctic Ocean (SHEBA) Project Office, Atmospheric Radiation Measurement program, and the National Center for Atmospheric Research are used to supplement this data
This data set is complete and provides direct observations of all terms of the surface energy budget of the multi-year SHEBA site: Fnet = Fatm + Fc study, with Pittsburgh located ~100 m from the ASFG flux tower and Quebec2 about 1300 m distant
Summary
The Arctic Ocean is a region approximately the size of the United States and whose climate is changing at a rate more rapidly than elsewhere on the globe. Persson et al (1999) showed that net longwave radiation over the wintertime Arctic sea ice has a bimodal distribution that was produced by the presence (or not) of liquid water in clouds, and that this bimodal cloud forcing produces large, sudden, surface temperature changes and bimodal responses in other surface energy budget terms These cloud–surface interactions have since been discussed by others who have suggested that these two radiative peaks represent distinct “atmospheric states” (e.g., Shupe and Intrieri 2004; Stramler et al 2011; Morrison et al 2012; Engström et al 2014).
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
