Observational Advances in Estimates of Oceanic Heating

Abstract

Since the early twenty-first century, improvements in understanding climate variability resulted from the growth of the ocean observing system. The potential for a closure of the Earth's energy budget has emerged with the unprecedented coverage of Argo profiling floats, which now provide a decade (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015) of invaluable information on ocean heat content changes above 2000 m. The expertise gained from Argo and repeat hydrography sections motivated the extension of the array toward the ocean bottom, which will progressively reveal the poorly known deep ocean and reduce the uncertainty of its presumed 10-15 % contribution to the 2006-2015 global ocean warming trend of 0.65-0.80 W m −2 . The sustainability and synergy of various observing systems helped to corroborate numerical models and decipher the internal variability of distinct ocean basins. Due to unique observations of the circulation in the North Atlantic, particular attention is paid to heat content changes and their relationship to dynamic variability in that region.

Climate-change–driven accelerated sea-level rise detected in the altimeter era

“…Constraining the thermosteric contribution to sea-level acceleration is hampered by the large discrepancies and related uncertainties that exist in ocean heat content datasets ( 20 , 29 ). The root cause of these discrepancies has been attributed to errors in the raw data and mapping methods used to infill data gaps, which are particularly large in the southern oceans, but substantial progress has been made recently in dealing with these issues ( 30 , 31 ). Given the systematic biases imparted by both data errors and infilling methods, a simple averaging across available datasets is not an effective means of minimizing bias ( 32 ).…”

The Argo Program: Present and Future

“…Deep ocean properties show significant large-scale trends on decadal time scales in some deep basins, with the strongest anomalies occurring at high latitudes Johnson, 2010, 2013;Desbruyères et al, 2016) near water mass formation regions. Globally, multidecadal depth-dependent trends below 2,000 m are 4−8 × 10 -3 degrees per decade in temperature (Purkey and Johnson, 2010).…”

“…The contribution of Argo to the global ocean observing system is synergistic with satellite altimetry and is assimilated to constrain ocean reanalyses and forecasts (Chang et al, 2013). The Argo data set puts strong constraints on the uptake of heat by the ocean due to anthropogenic climate change (Desbruyères et al, 2016). Argo has also significantly reduced the uncertainty in decadal rates of ocean heat uptake above 2,000 m (G.C.…”

Reconciling Estimates of Ocean Heating and Earth’s Radiation Budget

“…More recently, Desbruyères et al [26] have provided a review focussed on twenty-first century ocean measurements for insights into the planetary energy and sea level budgets. We refer the reader to these papers for a more extended discussion of this topic and limit our attention to summarising the key challenges for OHC change estimates and some of the most promising approaches.…”