New research has shown that more than 90% of the excess energy injected into the climate system in the past century has been absorbed by the ocean, resulting in significant warming, at all depths.
Using a new moored temperature time series, with data from February 2019 to August 2020, the study confirmed that warming trends previously observed in abyssal regions of the South Atlantic Ocean have persisted into recent years. The study examined the Vema Channel, a deep narrow passage in the South Atlantic bathymetry where most of the Antarctic bottom water in the South Atlantic flows northward. Published in Geophysical Research Letters, this data also suggests that warming may be occurring at an increasing rate since the early 2000s.
The study was conducted by an international collaboration of researchers including NOAA/AOML’s Renellys Perez and Shenfu Dong and was supported by the NOAA Climate Program Office’s (CPO) Climate Observations and Monitoring (COM) and Climate Variability and Predictability (CVP) programs.
The study’s abstract says, “Together with historical data, the combined record confirms the warming of the abyssal waters, with an increase of 0.059°C in potential temperature between January 1991 and August 2020, embedded within intense high-frequency variability. Moreover, the data suggests the possibility of accelerated warming, with a change in the temperature trend from 0.0016°C yr-1 , between the early 1990s and 2005, to 0.0026°C yr-1 afterward.”
“The excess heat absorbed from the atmosphere has increased the temperature in the upper layers of the ocean (up to 2,000m). In the abyss, infrequently repeated ship sections, deep Argo float measurements, and sparse moored observations have found signs of warming in the Southwest Atlantic, possibly linked to changes in the Weddell Sea.”
The study continues, “Water is an efficient temperature regulator. Large energy exchange is required to produce small changes in water temperature. Since 71% of the Earth’s surface is covered by oceanic water, the ocean plays a fundamentally important role in the climate system. The ocean transports, stores, and exchanges with the atmosphere substantial amounts of heat and freshwater. In this way, the ocean slows down and mitigates temperature variability in the climate system.
“However, in spite of its high thermal inertia, the ocean is also affected by global warming. More than 90% of the excess energy injected into the climate system in the past century has been absorbed by the ocean. As a result, the ocean has warmed significantly, at all depths. We report results of observations confirming that warming trends observed previously in abyssal regions of the South Atlantic persist into recent years in the Vema Channel. Our data also suggest that the warming may be occurring with an increasing rate since the early 2000s.”