Escalating Oceanic Temperatures: Record Highs for Global Sea Surface Heat

Data on Sea Surface Temperature Anomalies on August 21, 2023, from the Multiscale Ultrahigh Resolution Sea Surface Temperature (MUR SST) Initiative

Years of incremental warming attributed to anthropogenic climate change and a Pacific El Niño event have propelled global ocean temperatures to unprecedented highs in 2023.

In the spring of 2023, some geoscientists highlighted that the mean sea surface temperatures had exceeded previous peak levels recorded in a principal dataset overseen by NOAA. These elevated temperatures have sustained for months, registering a global sea surface temperature that was 0.99°C (1.78°F) above the norm in July—marking the fourth consecutive month of record-breaking heat.

Underlying Causes for the Surge

NASA researchers have scrutinized the root causes. Josh Willis, an oceanographer at NASA’s Jet Propulsion Laboratory (JPL), stated, “Two primary elements have escalated sea surface temperatures to new records: the emergence of an El Niño in the Pacific and the ongoing global warming that has consistently increased oceanic temperatures almost universally for a century.”

The introductory map of this article presents sea surface temperature anomalies as of August 21, 2023, where numerous regions were upwards of 3°C (5.4°F) warmer than their historical averages. Particularly, the equatorial zones of the central and eastern Pacific displayed unusually elevated temperatures, indicative of an emerging El Niño. This warmth is not isolated to the Pacific; extensive warm patches have also manifested near Japan in the Northwest Pacific, and near California and Oregon in the Northeast Pacific. Sections of the Indian, Southern, and Arctic Oceans have likewise exhibited abnormal heat.

Data Interpretation and Anomalies

The source of this map is the Multiscale Ultrahigh Resolution Sea Surface Temperature (MUR SST) project. Managed by JPL, the initiative amalgamates sea surface temperature measurements from a range of NASA, NOAA, and global satellites, supplemented by ship and buoy data. Rather than absolute temperatures, the map represents the anomaly between sea surface temperatures on August 21, 2023, and the average for that day from 2003-2014.

Gavin Schmidt, the director of NASA’s Goddard Institute for Space Studies, mentioned, “In the broader perspective, the escalation in heat and warmer sea surface temperatures are nearly entirely attributable to human activities—specifically, the substantial increase in greenhouse gas emissions since the onset of the industrial age.”

Deciphering the Patterns

Schmidt acknowledged that while other variables like weather patterns or aerosol distribution can have transient impacts on regional sea surface temperatures, they usually make a marginal contribution to the long-term global mean. Previous studies reveal that about 90 percent of the surplus heat generated by rising greenhouse gas levels is absorbed by the ocean, mainly at the surface.

According to Willis, the critical driver that catapulted sea surface temperatures to record levels in 2023 was the evolving Pacific El Niño. His analysis of the timing and intensity of anomalies in various regions relative to the global trend led him to this conclusion.

“The Pacific has had an outsized influence on this year’s global mean, given its vast expanse. It accounts for approximately half of the world’s total oceanic area,” Willis elaborated.

Marine Thermal Events

Defined as prolonged episodes of anomalously high sea temperatures, marine heat waves have recently affected numerous oceanic regions. A NOAA study found that 48% of the world’s oceans were undergoing a marine heat wave in August—setting a new record since data collection began in 1991.

Willis anticipates that the heat in the equatorial Pacific will be more enduring than many other marine heat waves observed globally. “The majority of marine heat waves are transient and superficial, often lasting only weeks and primarily driven by atmospheric conditions,” he explained.

The evolving El Niño in the equatorial Pacific, following three consecutive La Niña years, is predicted to weaken trade winds in a manner that will further augment surface water warming. According to NOAA forecasters, the odds exceed 95% that these El Niño conditions will persist through the winter season in the Northern Hemisphere.

Monitoring Mechanisms and Conclusion

Scientists at NOAA and NASA employ a range of tools—oceanic sensors, buoys, and multiple types of satellites—to monitor sea surface temperature changes and anomalies. Teams from NOAA’s Physical Sciences Laboratory, NOAA’s Coral Reef Watch, and NASA’s Jet Propulsion Laboratory closely follow marine heat waves and sea surface temperature deviations.

The graphical data in this article comes from NASA’s Multiscale Ultrahigh Resolution (MUR) initiative, and its video visualization was produced by NASA’s Scientific Visualization Studio, drawing on MUR data.

Frequently Asked Questions (FAQs) about Global Sea Surface Temperatures 2023

More about Global Sea Surface Temperatures 2023

• NASA’s Jet Propulsion Laboratory: Oceanography Research
• NOAA: Climate Change and Sea Surface Temperature
• Multiscale Ultrahigh Resolution Sea Surface Temperature (MUR SST) Project
• NASA’s Goddard Institute for Space Studies: Climate Research
• El Niño and its Global Impact
• Marine Heat Waves: An Emerging Threat
• NOAA’s Physical Sciences Laboratory: Sea Surface Temperature Monitoring
• NOAA’s Coral Reef Watch: Marine Heat Waves
• Anthropogenic Climate Change: A Global Overview
• NASA’s State of the Ocean Tool on Worldview