Global Oceans - [in State of the Climate in 2024]

Johnson, G. C.; Lumpkin, R.; Beckley, Brian; Bellas-Manley, Ashley; Carter, Brendan R.; Cetinić, Ivona; Chambers, Don P.; Chan, Duo; Cheng, Lijing; Dong, Shenfu; Feely, Richard A.; Franz, Bryan A.; Gao, Meng; Garg, Jay; Giglio, Donata; Graham, Garrett; Hamlington, Benjamin D.; Hobbs, Will; Hu, Zeng-Zhen; Huang, Boyin; Jersild, Annika; Jevrejeva, Svetlana ORCID: https://orcid.org/0000-0001-9490-4665; Johns, William E.; Killick, Rachel. E.; Kuusela, Mikael; Lamont, Tarron; Landerer, F. W.; Landschützer, Peter; Le Hénaff, Matthieu; Leuliette, Eric; Locarnini, Ricardo; Lyman, John M.; Merrifield, Mark A.; Mishonov, Alexey; Mitchum, Gary T.; Moat, Ben I. ORCID: https://orcid.org/0000-0001-8676-7779; Nerem, R. Steven; Oe, Mitsuho; Perez, Renellys C.; Reagan, James; Schlegal, Robert W.; Schmid, Claudia; Smeed, David A. ORCID: https://orcid.org/0000-0003-1740-1778; Smith, Ryan H.; Speich, Sabrina; Stackhouse, Paul W.; Sukianto, Thea; Sweet, William; Thompson, Philip R.; Triñanes, Joaquin A.; Tuchen, Franz Philip; Volkov, Denis L.; Wanninkhof, Rik; Weller, Robert A.; Westberry, Toby K.; Widlansky, Matthew J.; Willis, Joshua K.; Yin, Xungang; Yu, Lisan; Zhang, Huai-Min. 2025 Global Oceans - [in State of the Climate in 2024]. Bulletin of the American Meteorological Society, 106 (8). S173-S232. 10.1175/BAMS-D-25-0074.1

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Abstract/Summary

El Niño ebbed in early 2024, reaching neutral status in May and crossing the threshold into La Niña conditions in December. The global average annual sea surface temperature was 0.06°C above the previous record set in 2023. Marine heatwaves in 2024 were, as in 2023, more widespread, long-lived, and severe than in previous years. From 2023 to 2024, ocean heat content from 0 dbar to 2000 dbar increased at a rate equivalent to ~1.5 W m−2 of heat applied over the ocean surface, and global sea level increased by 4.6 (±1.4) mm, both reaching record-high levels in 2024. Maps of air–sea flux data estimate that the oceans absorbed carbon at a rate of ~2.7 Pg C yr−1 in 2024, which was below the 2014–23 average of ~3.7 Pg C yr−1. In the Pacific Ocean, given the shift from a strong El Niño to weak La Niña conditions, surface currents across the equatorial Pacific in 2024 were strongly anomalously westward, and sea surface temperatures, sea surface salinities, 0 m–2000 m ocean heat content, and sea level all decreased sharply in the eastern equatorial Pacific from 2023 to 2024. Fluxes of carbon dioxide from ocean to atmosphere were anomalously lower than average during 2024 off Peru and out to about 140°W, likely owing to the El Niño in the first few months of the year. As in 2023, chlorophyll-a anomalies in 2024 were low in a wedge in the central and eastern equatorial Pacific, but high just outside that wedge. The Pacific Decadal Oscillation has been in a negative phase since 2020, with sea surface temperature, ocean heat content, and sea surface height values in the center of the North Pacific basin all higher than average, along with relatively lower values around the edges in 2024. A persistent 2020–24 poleward shift in the Kuroshio extension also continued to be evident east of Japan in both ocean heat content and zonal surface current anomalies. In the Indian Ocean, sea surface temperature, ocean heat content, and sea level were all above average in 2024 across much of the basin, except for a large patch of below-average ocean heat content along 20°S–30°S. Surface currents near the equator were anomalously eastward. Surface salinities were primarily strongly anomalously fresh north of about 12°S in 2024, consistent with anomalously high freshwater input (precipitation minus evaporation) from the atmosphere to the ocean in the region. Chlorophyll-a anomalies were quite negative offshore of Somalia and Oman, as well as northeast of Madagascar, but generally positive in the rest of the basin. There was also a prominent ridge of high sea level and ocean heat content extending eastward from Africa just north of Madagascar, which was associated with anomalous westward surface currents on its northern flank. In the Atlantic, sea surface temperature, ocean heat content, and sea level were all well above average across much of the basin in 2024, with some below-average values of ocean heat content in a patch extending from east of Cape Cod to about 55°N, 25°W. A band of anomalously eastward surface current and above-average ocean heat content directly north of a band of anomalously westward surface current along the Gulf Stream extension west of 70°W is consistent with an anomalous northward shift of the axis of this current in 2024. Sea surface salinity was anomalously high in much of the basin but anomalously low around the Intertropical Convergence Zone and in the Labrador Sea. Updates of time series of the Atlantic meridional overturning circulation at two latitudes revealed little evidence of a trend over the past few decades.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1175/BAMS-D-25-0074.1
ISSN:	0003-0007
NORA Subject Terms:	Marine Sciences
Date made live:	10 Nov 2025 12:19 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/540537

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