Authors:

LIJING CHENG

International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, and University of Chinese Academy of Sciences, Beijing, China

JIANG ZHU

International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China

Abstract:

Assessment of the upper-ocean (0–700 m) heat content (OHC) is a key task for monitoring climate change. However, irregular spatial and temporal distribution of historical subsurface observations has induced uncertainties in OHC estimation. In this study, a new source of uncertainties in calculating OHC due to the insufficiency of vertical resolution in historical ocean subsurface temperature profile observations was diagnosed. This error was examined by sampling a high-vertical-resolution climatological ocean according to the depth intervals of in situ subsurface observations, and then the error was defined as the difference between the OHC calculated by subsampled profiles and the OHC of the climatological ocean. The obtained resolution-induced error appeared to be cold in the upper 100 m (with a peak of approximately20.18C), warm within 100–700 m (with a peak of;0.18C near 180 m), and warm when averaged over 0–700-m depths (with a global average of;0.018–0.0258C,;1–2.531022 J). Geographically, it showed a warm bias within 308S–308N and a cold bias at higher latitudes in both hemispheres, the sign of which depended on the concave or convex shape of the vertical temperature profiles. Finally, the authors recommend maintaining an unbiased observation system in the future: a minimal vertical depth bin of 5% of the depth was needed to reduce the vertical-resolution-induced bias to less than 0.0058C on global average (equal to Argo accuracy)

Key words:

Citation:

LIJING CHENG,JIANG ZHU.JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY,DOI: 10.1175/JTECH-D-13-00220.1