Global Oceans, BAMS State of the Climate in 2021, Chapter 3

Johnson, Gregory C.; Lumpkin, Rick; Boyer, Tim; Bringas, Francis; Cetinić, Ivona; Chambers, Don P.; Cheng, Lijing; Dong, Shenfu; Feely, Richard A.; Fox-Kemper, Baylor; Frajka-Williams, Eleanor ORCID: https://orcid.org/0000-0001-8773-7838; Franz, Bryan A.; Fu, Yao; Gao, Meng; Garg, Jay; Gilson, John; Goni, Gustavo; Hamlington, Benjamin D.; Hewitt, Helene T.; Hobbs, William R.; Hu, Zeng-Zhen; Huang, Boyin; Jevrejeva, Svetlana ORCID: https://orcid.org/0000-0001-9490-4665; Johns, William E.; Katsunari, Sato; Kennedy, John J.; Kersalé, Marion; Killick, Rachel E.; Leuliette, Eric; Locarnini, Ricardo; Lozier, M. Susan; 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; Notz, Dirk; Perez, Renellys C.; Purkey, Sarah G.; Rayner, Darren ORCID: https://orcid.org/0000-0002-2283-4140; Reagan, James; Schmid, Claudia; Siegel, David A.; Smeed, David A. ORCID: https://orcid.org/0000-0003-1740-1778; Stackhouse, Paul W.; Sweet, William; Thompson, Philip R.; Volkov, Denis L.; Wanninkhof, Rik; Weller, Robert A.; Wen, Caihong; Westberry, Toby K.; Widlansky, Matthew J.; Willis, Josh K.; Yu, Lisan; Zhang, Huai-Min. 2022 Global Oceans, BAMS State of the Climate in 2021, Chapter 3. Bulletin of the American Meteorological Society, 103 (8). S143-S192. https://doi.org/10.1175/BAMS-D-22-0072.1

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Official URL: http://dx.doi.org/10.1175/BAMS-D-22-0072.1

Abstract/Summary

Patterns of variability in ocean properties are often closely related to large-scale climate pattern indices, and 2021 is no exception. The year 2021 started and ended with La Niña conditions, charmingly dubbed a “double-dip” La Niña. Hence, stronger-than-normal easterly trade winds in the tropical south Pacific drove westward surface current anomalies in the equatorial Pacific; reduced sea surface temperature (SST) and upper ocean heat content in the eastern tropical Pacific; increased sea level, upper ocean heat content, and salinity in the western tropical Pacific; resulted in a rim of anomalously high chlorophyll-a (Chla) on the poleward and westward edges of the anomalously cold SST wedge in the eastern equatorial Pacific; and increased precipitation over the Maritime Continent. The Pacific decadal oscillation remained strongly in a negative phase in 2021, with negative SST and upper ocean heat content anomalies around the eastern and equatorial edges of the North Pacific and positive anomalies in the center associated with low Chla anomalies. The South Pacific exhibited similar patterns. Fresh anomalies in the northeastern Pacific shifted towards the west coast of North America. The Indian Ocean dipole (IOD) was weakly negative in 2021, with small positive SST anomalies in the east and nearly-average anomalies in the west. Nonetheless, upper ocean heat content was anomalously high in the west and lower in the east, with anomalously high freshwater flux and low sea surface salinities (SSS) in the east, and the opposite pattern in the west, as might be expected during a negative phase of that climate index. In the Atlantic, the only substantial cold anomaly in SST and upper ocean heat content persisted east of Greenland in 2021, where SSS was also low, all despite the weak winds and strong surface heat flux anomalies into the ocean expected during a negative phase of the North Atlantic Oscillation. These anomalies held throughout much of 2021. An Atlantic and Benguela Niño were both evident, with above-average SST anomalies in the eastern equatorial Atlantic and the west coast of southern Africa. Over much of the rest of the Atlantic, SSTs, upper ocean heat content, and sea level anomalies were above average. Anthropogenic climate change involves long-term trends, as this year’s chapter sidebars emphasize. The sidebars relate some of the latest IPCC ocean-related assessments (including carbon, the section on which is taking a hiatus from our report this year). This chapter estimates that SST increased at a rate of 0.16–0.19°C decade−1 from 2000 to 2021, 0–2000-m ocean heat content warmed by 0.57–0.73 W m−2 (applied over Earth’s surface area) from 1993 to 2021, and global mean sea level increased at a rate of 3.4 ± 0.4 mm yr−1 from 1993 to 2021. Global mean SST, which is more subject to interannual variations than ocean heat content and sea level, with values typically reduced during La Niña, was ~0.1°C lower in 2021 than in 2020. However, from 2020 to 2021, annual average ocean heat content from 0 to 2000 dbar increased at a rate of ~0.95 W m−2, and global sea level increased by ~4.9 mm. Both were the highest on record in 2021, and with year-on-year increases substantially exceeding their trend rates of recent decades.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1175/BAMS-D-22-0072.1
ISSN:	0003-0007
Date made live:	21 Sep 2022 09:20 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/533242

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1175/BAMS-D-22-0072.1

ISSN:

0003-0007

Date made live:

21 Sep 2022 09:20 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/533242