Mechanisms controlling global mean sea surface temperature determined from a state estimate
MetadataShow full item record
KeywordSea surface temperature
Global mean sea surface temperature ((T) over bar) is a variable of primary interest in studies of climate variability and change. The temporal evolution of (T) over bar) can be influenced by surface heat fluxes ((F) over bar)) and by diffusion ((D) over bar)) and advection ((A) over bar)) processes internal to the ocean, but quantifying the contribution of these different factors from data alone is prone to substantial uncertainties. Here we derive a closed (T) over bar) budget for the period 1993-2015 based on a global ocean state estimate, which is an exact solution of a general circulation model constrained to most extant ocean observations through advanced optimization methods. The estimated average temperature of the top (10-m thick) level in the model, taken to represent (T) over bar), shows relatively small variability at most time scales compared to (F) over bar), (D) over bar), or (A) over bar), reflecting the tendency for largely balancing effects from all the latter terms. The seasonal cycle in (T) over bar) is mostly determined by small imbalances between (F) over bar) and (D) over bar), with negligible contributions from (A) over bar). While (D) over bar) seems to simply damp (F) over bar) at the annual period, a different dynamical role for (D) over bar) at semiannual period is suggested by it being larger than (F) over bar). At periods longer than annual, (A) over bar) contributes importantly to (T) over bar) variability, pointing to the direct influence of the variable ocean circulation on (T) over bar) and mean surface climate. Plain Language Summary Global mean sea surface temperature (T) over bar) is a key metric when defining the Earth's climate. Determining what controls the evolution of (T) over bar )T is thus vital for understanding past climate variability and predicting its future evolution. Processes that control (T) over bar) involve forcing surface heat fluxes, as well as advection and diffusion of heat internal to the ocean, but their relative contributions are poorly known and difficult to assess from observations alone. Here we use advanced methods to combine models and data and derive a closed budget for (T) over bar) variability in terms of the forcing, advection, and diffusion processes. The estimated (T) over bar) shows relatively small variability compared to surface forcing, advection, or diffusion, reflecting the tendency for largely balancing effects from all the latter terms. The seasonal cycle in (T) over bar) is mostly determined by small imbalances between forcing and diffusion, with negligible contributions from advection. Diffusion does not always act as a simple damping of forcing surface fluxes, however. In addition, at periods longer than annual, advection contributes importantly to (T) over bar) variability. The results point to the direct influence of the variable ocean circulation on (T) over bar) and the Earth's surface climate.
Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 45 (2018): 3221-3227, doi:10.1002/2017GL076821.
The publisher requires that this item be embargoed until 2018-09-25. Please check back after 2018-09-25.
Suggested CitationArticle: Ponte, Rui Vasques de Melo, Piecuch, Christopher G., "Mechanisms controlling global mean sea surface temperature determined from a state estimate", Geophysical Research Letters 45 (2018): 3221-3227, DOI:10.1002/2017GL076821, https://hdl.handle.net/1912/10450
Showing items related by title, author, creator and subject.
Role of net surface heat flux in seasonal variations of sea surface temperature in the tropical Atlantic Ocean Yu, Lisan; Jin, Xiangze; Weller, Robert A. (American Meteorological Society, 2006-12-01)The present study used a new net surface heat flux (Qnet) product obtained from the Objective Analyzed Air–Sea Fluxes (OAFlux) project and the International Satellite Cloud Climatology Project (ISCCP) to examine two specific ...
Ocean preconditioning of Cyclone Nargis in the Bay of Bengal : interaction between Rossby waves, surface fresh waters, and sea surface temperatures Yu, Lisan; McPhaden, Michael J. (American Meteorological Society, 2011-09)An in-depth data analysis was conducted to understand the occurrence of a strong sea surface temperature (SST) front in the central Bay of Bengal before the formation of Cyclone Nargis in April 2008. Nargis changed its ...
Global temperature calibration of the alkenone unsaturation index (UK′37) in surface waters and comparison with surface sediments Conte, Maureen H.; Sicre, Marie-Alexandrine; Ruhlemann, Carsten; Weber, John C.; Schulte, Sonja; Schulz-Bull, Detlef; Blanz, Thomas (American Geophysical Union, 2006-02-07)In this paper, we compile the current surface seawater C37 alkenone unsaturation (UK′37) measurements (n=629, −1 to 30°C temperature range) to derive a global, field-based calibration of UK′37 with alkenone production ...