[A-CG41] Satellite Earth Environment Observation

[ACG41-15] Recent years change in North Pacific observed by GCOM-C “SHIKISAI”

*Hiroshi Murakami¹ (1.Earth Observation Research Center, Japan Aerospace Exploration Agency)

Keywords:GCOM-C, SHIKISAI, time series analysis, North Pacific

Second-generation Global Imager (SGLI) aboard the JAXA Global Change Observation Mission - Climate (GCOM-C) has been observing global environmental variables, such as sea surface temperature (SST), chlorophyll-a concentration (CHL), solar radiation (SWR), clouds, aerosols, land surface temperature, vegetation index, snow, ice cover, and surface albedo, since the start of observations in January 2018. The data products are continuously improved [1], verified [2], and published on JAXA's data portal sites G-portal [3] and JASMES [4]. In order to monitor long-term variability and improve understanding of climate change, which is a key purpose of GCOM, we have started combined time series analysis with other satellite sensors. In this presentation, we will introduce the SST, SWR and CHL change in the North Pacific Ocean in recent years using the 25-year monthly time series. According to the last El Niño which started in the spring of 2023 and ended in the spring of 2024, the global monthly SST (60N~60S average) reached its highest value in July 2023, the monthly anomaly became highest in January 2024, and it has returned to the normal level of the long-term increase trend (about 0.02K/y). On the other hand, the SST anomaly near Japan and North Pacific remained high in 2024. The highest temperature anomaly of about +7.5°C at maximum off the coast of Tohoku (142.0~144E, +37.5~40.5N) in January-May 2024, and around North Pacific subarctic front (160E~185W, 35~45N) showed a highest value of about +3.5°C in September-October 2025. In addition to continuous increase of SST since 2020, the short-term high anomaly of SST in September-October 2024 seems to correspond to the SWR increase (SST increased about two months behind of SWR). On the other hand, SST did not correlate with SWR off the coast of Tohoku but correspond to the distribution of Kuroshio extension water which distributed further north than normal in 2023-2024. CHL in both areas decreased in negative correlation with the SST increase. The estimate of CHL might be influenced by error of sensor calibration, however consistent results among other sensors, SGLI, MODIS, VIIRS, and OLCI, support the reliability of CHL changes described here. GCOM-C has been in operation for more than seven years, and it will continue accumulation of longer-term data to monitor the coming global environmental changes.
References:
[1] GOCM-C homepage: Products & Algorithms, https://suzaku.eorc.jaxa.jp/GCOM_C/data/product_std.html.
[2] GOCM-C homepage: Validation, https://suzaku.eorc.jaxa.jp/GCOM_C/data/validation.html.
[3] JAXA G-portal: https://gportal.jaxa.jp/gpr/.
[4] JASMES homepage: https://kuroshio.eorc.jaxa.jp/JASMES/.