Ocean heat content (OHC) change contributes substantially to global sea level rise (30%~50%), and provides a key metric for the earth’s energy budget (90% of the earth’s energy imbalance is stored in the ocean), so it is a vital task for the climate research community to estimate historical OHC. While there are large uncertainties regarding its value. IPCC AR5 provided five independent estimates of historical OHC change from 1970 to 2010 by five different international groups ranging from 74TW~137TW. Among these values, the minimum is as much as a half of the maximum, implying large divergence in the assessment of the ocean warming rate. That’s because there are several major error sources during OHC estimation.
Dr. Cheng Lijing, Prof. Zhu Jiang from IAP carried out a series of studies examining and quantifying the error sources in OHC estimates. These improvements lead to a new reconstruction of historical upper (0–700 m) OHC change.
Chen and Zhu worked with John Abraham from University of St. Thomas, USA, and obtained upper 0–700 m OHC trend which is 0.55 ± 0.14 × 1022 J yr−1 (168TW) from 1970 to 2014, stronger than IPCC-AR5’s estimates. The long-term trend reveals the signal of anthropogenic forcing since industrial revolution, and inter-annual variability is dominated by El Niño-Southern Oscillation (ENSO). Furthermore, they show that Coupled Model Intercomparison Project, Phase 5 (CMIP5) simulations have limited ability in capturing the interannual and decadal variability of historical upper OHC changes during the past 45 years.
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