Headline:
Scientists Develop Novel Method to Estimate Meridional Atlantic Freshwater Transport at Various Latitudes
Article:
In a groundbreaking development, researchers from the Institute of Physical Science and Technology of the Chinese Academy of Sciences and Xiamen University have developed an indirect method to estimate the meridional Atlantic freshwater transport (AMFT) across various latitudes. This pioneering study is published in Geophysical Research Letters.
Oceans, inhabitants of 97% of Earth’s water, play a crucial role in the global water cycle. They exchange water with the atmosphere, land, and cryosphere, with these interactions directly reflected in ocean salinity changes.
As a result, ocean salinity variations are often represented as changes in freshwater content in theoretical studies, providing a holistic framework for estimating Earth’s water cycle and understanding global water system dynamics.
The redistribution of freshwater in oceans, primarily driven by freshwater transport, is a significant part of Earth’s water cycle. The Atlantic Ocean, specifically, plays a vital role due to changes in freshwater content in the subpolar North Atlantic, which not only reflect regional freshwater exchange but also impact global ocean circulation.
However, current AMFT observations are limited to specific latitude bands (between 26°N and around 55°N) due to high associated costs of establishing observation arrays. This limited coverage significantly hinders understanding of AMFT variability and underlying mechanisms.
To overcome this challenge, the research team analyzed ocean freshwater content, derived from salinity, along with surface freshwater flux (precipitation and evaporation) and AMFT at 26.5°N (RAPID array).
Ocean freshwater content is influenced by surface freshwater flux and AMFT convergence. Therefore, AMFT can be calculated by subtracting surface freshwater flux from ocean freshwater content changes. Using this method, monthly AMFT estimates were obtained for the range 34°S to 66°N from 2004 to 2020.
Climatologically, AMFT extends southward between 18°S and 34°S, and northward from 18°N to 66°N. Interannually, AMFT shows different variabilities between 34°S and 40°N, and between 40°N and 66°N, potentially due to changes in AMFT driving factors in these regions.
Notably, the new estimates reveal a trend of increasing AMFT intensity northward across different latitudes between 2004 and 2020, although the time span is relatively short. However, this trend’s strength varies with latitude, resulting in convergence and divergence areas in AMFT that impact Atlantic freshwater content changes.
This method effectively addresses the limitation of observation dataset coverage, providing valuable data for deeper understanding of global warming-induced AMFT changes.
Reference:
Huayi Zheng et al., Estimate of south Atlantic freshwater transport based on observations, Geophysical Research Letters (2024). DOI: 10.1029/2024GL110021
