Seasonal Change of the Atmospheric Heat Budget over the Southern Ocean from ECMWF and ERBE Data

Abstract

The seasonal variation of the zonally averaged atmospheric energy budget between 60Њ and 70ЊS was estimated. This region is predominantly within the seasonal sea ice zone of the Southern Ocean, including some parts of the Antarctic continent. In the Southern Ocean, seasonal sea ice extent exhibits large amplitudes and affects the surface heat exchange considerably. Seasonal variation of the energy budget and its relationship to the surface condition should be clarified as the basic variation. In spite of its importance, the data to estimate energy budgets are extremely sparse in this sea ice zone. Hence, the global objective analyses with forecasting models are mainly used as data for the present study. The surface energy flux is obtained as a remainder term in the energy budget of the total atmosphere, with the energy divergence and changes to the energy content of the atmospheric column derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) objective analyses, and with the radiation budget at the top of the atmosphere estimated from the Earth Radiation Budget Experiment (ERBE) data.The derived values of the surface flux are not seasonally symmetric. This differs from other latitude bands (e.g., 50Њ-60ЊS) where the variation is symmetric and is driven by shortwave radiation change. The monthly mean surface energy flux shows an immediate increase to the maximum of 116 W m Ϫ2 in May (heating of the atmosphere), and then gradually decreases to the minimum of Ϫ108 W m Ϫ2 in December (cooling of the atmosphere). It is suggested that the asymmetry at 60Њ-70ЊS is due to the effect of seasonal sea ice extent changes on the surface energy exchanges. A comparison of the derived values of the surface flux with the latent heat required for the change in sea ice extent provides some support for this suggestion. The rate of sea ice expansion shows a peak in May when the surface energy flux becomes maximum. The turbulent heat component of the surface energy flux is compared with other estimates of turbulent heat exchange over the Southern Ocean. Suppression of the turbulent heat exchange in late winter derived in the present study, in comparison with those values over open water area, suggests the effect of extended sea ice cover.

Spatial and temporal operation of the Scotia Sea ecosystem: a review of large-scale links in a krill centred food web

“…Within this flow regime, the other major factor that determines the structure of the ecosystem is the marked seasonality of polar environments (Clarke 1988). Changes in solar irradiance and associated fluctuations in sea ice cover result in strong seasonal variation in upper ocean temperature and light levels (Okada & Yamanouchi 2002). This seasonal variation dominates the operation of Southern Ocean ecosystems in a number of ways.…”

The Antarctic Atmospheric Energy Budget. Part I: Climatology and Intraseasonal-to-Interannual Variability

“…Several previous studies have estimated the Antarctic atmospheric energy budget relying to different degrees on observations, reanalyses, and climate models (Nakamura and Oort 1988, hereafter NO88;Genthon and Krinner 1998;Okada and Yamanouchi 2002;van de Berg et al 2007;Cullather and Bosilovich 2012, hereafter CB12). Here, we construct the energy budget using satellite observations from the Clouds and the Earth's Radiant Energy System (CERES; Wielicki et al 1996) and data from the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim; Dee et al 2011).…”

Interannual and intraseasonal variations of the energy budget over the polar regions and its climatic implications

“…The energy change in the polar regions consists of variations over multiple timescales. However, compared to the interannual (e.g., ) and annual (e.g., Masuda 1990;Okada and Yamanouchi 2002; variations of the polar energy budget, intraseasonal variations have not been well examined. To improve our understanding of polar climate and its global interactions, this study is designed to explore possible remote impacts of the intraseasonal timescale tropical energy change on the polar energy budget.…”