Earth's Energy Imbalance From the Ocean Perspective (2005–2019). Issue 16 (23rd August 2021)

• Record Type: Journal Article
• Authors: Hakuba, M. Z.; Frederikse, T.; Landerer, F. W.
• Is Part Of: Geophysical research letters. Volume 48:Issue 16(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-23
• Subjects: Earth's energy imbalance -- sea level budget -- Geodesy -- ocean heat uptake -- thermal expansion; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL093624
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Earth's energy imbalance (EEI) represents the rate of global energy accumulation in response to radiative forcings and feedbacks. Ocean heat uptake (OHU) poses a vital constraint on EEI and its uncertainty. Considering recent geodetic observations, geophysical corrections, and new estimates of the ocean's expansion efficiency of heat, we translate steric sea‐level change, the difference of total sea‐level and ocean‐mass change, into an OHU of 0.86 [0.62, 1.10, 5%–95%] Wm −2 for the period 2005–2019. Adding components of non‐oceanic heat uptake, we obtain an EEI of 0.94 [0.70, 1.19] Wm −2, which is at the upper end of previous assessments, but agrees within uncertainty. Interannual geodetic OHU variability exhibits a higher correlation with top‐of‐the‐atmosphere net radiative flux than hydrographic‐only data, but has a three times larger standard deviation. The radiation fluxes and the geodetic approach suggest an increase in heat uptake since 2005, most markedly in recent years. Plain Language Summary: As the Earth is warming in response to increasing greenhouse gas concentrations, 90% of the extra heat is deposited in the world's oceans. This heat accumulation in the ocean can be used to estimate Earth's energy imbalance (EEI), which quantifies the energy uptake or deficit of our planet. Profiles of ocean temperature measured with profiling floats are often used to calculate the ocean heat uptake, but this approach does not sample the deep ocean (below 2, 000 m) and misses some areas near coasts. Alternatively, the ocean's thermal expansion can be related to the heat uptake and is obtained by subtracting satellite‐observed ocean mass changes due to ice‐sheet and glacier melt, from total sea‐level changes. Using the newest data and methods over the recent two decades, we find that EEI (0.94 Wm −2 ) derived from the satellite data is slightly larger than that from the ocean float measurements (0.76 Wm −2 ). But despite the higher central value, both are equivalent within uncertainty. Key Points: We assess the sea‐level budget and its implications on Earth's energy imbalance (EEI) over 2005–2019 Space geodesy suggests an EEI of 0.94 ± 0.24 Wm −2 Multiple approaches suggest that heat uptake is increasing most markedly in recent years