Press Releases
JAMSTEC
Sea-ice data improves climate prediction over the Antarctic Seas
– Applicability to Northern Hemisphere climate prediction –
Abstract:
Dr. Yushi Morioka (JAMSTEC Application Laboratory) and his research team have successfully improved prediction accuracy of sea-ice and climate variability over the Weddell Sea, one of the Antarctic Seas, by incorporating satellite data of sea-ice concentration into a climate model and performing re-forecast experiments over the past 30 years.
Weddell Sea (Fig. 1), located east of the Antarctic Peninsula, is covered in the greatest extent of sea-ice among the Antarctic Seas during austral winter (Jul-Sep). Through the generation of cold and saline Antarctic Bottom Water, it plays an important role in maintaining the global ocean thermohaline circulation (*1). In contrast to the Arctic Sea, which has witnessed a significant decrease in sea-ice cover due to the recent global warming, the sea-ice extent over the Antarctic Seas, including that over the Weddell Sea, has not shown a significant increasing or decreasing trend; rather, it has exhibited pronounced interannual variability. In particular, a recent study suggests that during austral spring (Oct-Dec), when the sea-ice starts to retreat, the lower-than-normal sea-ice cover over the Weddell Sea changes the surface-air temperature and surface wind in surrounding regions such as the Antarctic Peninsula and the South Atlantic. However, the potential impact of interannual sea-ice variability on seasonal climate prediction accuracy remains poorly understood.
To address this issue, Dr. Morioka and the research team performed two types of re-forecast experiments over the past 30 years using a climate model (SINTEX-F2; *2), which was originally developed as a collaboration between EU agencies and JAMSTEC. The control experiment (CTR) was set to the initialization of the model’s sea-surface temperature using the observation data, while the sea-ice restoring (SIR) experiment additionally incorporated the initialization of the model’s sea-ice concentration, which was derived from satellite observations. Compared to the CTR experiment, the SIR experiment shows significant improvement in terms of prediction skills needed for predicting sea-ice concentration over the Weddell Sea up to four months ahead (Figs. 2 and 3) from the Sep 1st initialization. It was also found that the improvement in the sea-ice prediction over the Weddell Sea during austral spring leads to corresponding improvements in the surface-air temperature and surface wind prediction for the surrounding regions (Figs. 4 and 5).
Given that the extent of sea-ice cover influences the high-latitude climate variability over the Antarctic Seas, including that in the Weddell Sea, it is imperative to accurately predict sea-ice variability using climate models. The findings of this study underline the importance of sea-ice observations, which help improve the prediction skills of the climate models for sea-ice and climate variability at high latitudes. The scientific findings and initialization schemes developed in this study are applicable to high-latitude climate prediction in the Southern and Northern hemispheres.
This study was conducted with support from the Science and Technology Research Partnership for Sustainable Development (SATREPS) of the Japan Agency for Medical Research and Development (AMED) and Japan International Cooperation Agency (JICA). It was also supported by the Grant-in-aid for early career scientist (B) program (IP15K17768) by the Japan Society for the Promotion of Science (JSPS).
This work will be published in Scientific Reports on February 25, 2019 (19:00 JST).
Title：Role of sea-ice initialization in climate predictability over Weddell Sea
Authors：Yushi Morioka1, Takeshi Doi1, Doroteaciro Iovino2, Simona Masina2, Swadhin K. Behera1
Affiliations: 1. Application Laboratory JAMSTEC 2. Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC)
https://www.nature.com/articles/s41598-019-39421-w
*1 Thermohaline Circulation: Global ocean circulation arising from hemispheric differences in the ocean density. In the high latitudes, sea water subducts into deep ocean because of decrease in ocean temperature and increase in salinity.
*2 SINTEX-F2 climate model: Global climate simulation and prediction system installed on the Earth Simulator, which was collaboratively developed by EU research agencies and JAMSTEC. ‘Climate model’ refers to a series of computer programs that describe physical processes of air-sea-ice-land interaction, which influence climate. The SINTEX-F2 model, developed in 2012, is a successor to the original SINTEX-F1 model, which includes a sea-ice dynamical model with increased spatial resolution for atmospheric and oceanic models (approx. 50-100 km horizontal resolution).
Figure 1: Antarctic sea-ice concentration (in %) during Oct-Dec 1982-2016.
Figure 2: (a) Prediction skills of the Antarctic sea-ice concentration (SIC) model during the Oct-Dec season for the CTR experiment initialized every September 1st from 1982 to 2015. The skills were evaluated against the correlation between the SIC observation data and the predicted SIC anomalies. (b) Same as in (a), but for the prediction skills associated with the sea-ice restoring (SIR) experiment. (c) Differences between the prediction skills in the SIR and CTR experiments.
Figure 3: Composite sea-ice concentration (SIC, in %) anomalies during the Oct-Dec season of the low sea-ice years (1996, 1998, 1999, 2001, 2010) in the Weddell Sea. (b) SIC anomalies predicted in the CTR experiments initialized every September 1st during the low sea-ice years in the Weddell Sea. (c) Same as in (b), but for the SIC anomalies predicted in the SIR experiments. (d) Differences in between the SIC anomalies predicted in the SIR experiment and that predicted in the CTR experiment.
Figure 4: Composite surface air-temperature (SAT, in ºC) anomalies during the Oct-Dec season of the low sea-ice years (1996, 1998, 1999, 2001, 2010) in the Weddell Sea. (b) SAT anomalies predicted in the CTR experiments initialized every Sep 1st of the low sea-ice years in the Weddell Sea. (c) Same as in (b), but for the SAT anomalies predicted in the SIR experiments. (d) Differences between the SAT anomalies predicted in the SIR experiments and those in the CTR experiments.
Figure 5: Composite sea-level pressure (SLP, color in hPa) and surface wind anomalies at 10 m height (arrows, in m s-1) during the Oct-Dec season of the low sea-ice years (1996, 1998, 1999, 2001, 2010) in the Weddell Sea. (b) SLP and wind anomalies predicted in the CTR experiments initialized every Sep 1st in the low sea-ice years. (c) Same as in (b), but for the SLP and wind anomalies predicted in the SIR experiments. (d) Differences between the predicted SLP and wind anomalies in the SIR and CTR experiments.
Contacts:
- (For this study)
- Yushi Morioka, Scientist, Application Laboratory
- (For press release)
- Tsuyoshi Noguchi, Manager, Press Division, Public Relations Department