Arctic cyclogenesis at the marginal ice zone: A contributory mechanism for the temperature amplification?

Abstract

[1] Rapid sea-ice retreat over the Arctic Ocean has a leading role in Arctic amplification. The sea-ice extent dramatically recovers during every freezing season, so despite the recent summer sea-ice retreat, there must be extraordinary heat exchange between the lower atmosphere and upper ocean. However, the underlying mechanisms for this remain uncertain. Here we show that autumn frontal cyclogenesis is a crucial event in the Arctic air-sea coupled system. Our shipboard Doppler radar and intensive radiosonde observations at the marginal ice zone detected an explosive frontal cyclogenesis, with coupling between upper and lower tropospheric vortices. The thermal contrast between ocean and ice surfaces is likely favorable to cyclogenesis with an identical life-cycle to that at mid-latitudes. This suggests a northward shift of meridional heat transport. The 1.5 K temperature decrease in the upper ocean after the cold front has passed reveals that a large amount of heat is transported into the atmosphere. This is an invaluable example of the fact that sea ice retreat contributes to polar amplification of surface air temperature increase. Citation: Inoue, J., and M. E. Hori (2011), Arctic cyclogenesis at the marginal ice zone: A contributory mechanism for the temperature amplification?, Geophys.

Recent Arctic amplification and extreme mid-latitude weather

“…However, during autumn when the air cools to temperatures lower than the ocean surface, the excess heat absorbed during summer is transferred from the ocean to the atmosphere via radiative and turbulent fluxes, which strongly warms the lower Arctic troposphere. The additional heat in the system slows the formation of sea ice through winter, both in extent and, especially, thickness 23,24 . Hence, winter sea ice has thinned 2 , enabling easier melting, fracturing and/or mobility of the ice cover.…”

The open-ocean sensible heat flux and its significance for Arctic boundary layer mixing during early fall

“…During late summer and early fall, the turbulent heat loss from the ocean is considered important for initiating refreeze processes (Inoue and Hori, 2011;Tietsche et al, 2011). Our study shows that the efficiency of turbulent heat exchange has not increased substantially over the regions that have recently experienced accelerated summer sea ice loss.…”

“…more northern latitudes compared to earlier years ( Fig. 1; Sato et al, 2012;Inoue and Hori, 2011). The year 2013, however, is an exception when observations were primarily collected at a fixed point (72.75 • N and 168.25 • W) as part of the Arctic Research Collaboration for the Radiosonde Observing System (ARCROSE) experiment Kawaguchi et al, 2015).…”

“…Ship-based observations during the fall of 2010 have similarly indicated the importance of the ocean sensible heat flux for the onset of the annual freeze cycle (Inoue and Hori, 2011). The authors suggested that the cold air outbreak in the wake of cyclogenesis enabled significant cooling of the upper ocean (and freeze onset; Inoue and Hori, 2011). Presently, however, there is limited observational guidance for the open-ocean heat fluxes and the efficiency of turbulent heat exchange during such events.…”

“…Models also project that future occurrences of CAA may spread further poleward along the retreating sea ice margin (Kolstad and Bracegirdle, 2008). In spite of recent observations and modeling efforts (Inoue and Hori, 2011;Klein et al, 2009), there are limited measurements of actual surface fluxes during such events. In the following sections, using ship-based measurements, we investigate the instantaneous relationship between the SSHF and the BL height, which qualitatively represents the efficiency of turbulent heat exchange between the ocean and the atmosphere.…”