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Abstract Previous studies have suggested that variability in the Gulf Stream (GS) region can lead North Atlantic atmospheric variability. However, it remains unclear what GS characteristic is most important in driving this lead time. Here, we show that the GS sensible heat flux (SHF) gradient specifically leads the North Atlantic Oscillation (NAO) by 1 month. This lag relationship occurs only when climatological sea‐surface temperature and SHF gradients are largest in late winter. Further analysis reveals that fine‐scale gradients (∼50 km) are critical. A month prior to a negative NAO, stronger than normal diabatic frontogenesis associated with anomalously strong SHF gradients is observed over the separated GS region. This is collocated with a North Atlantic eddy‐driven jet located in its Southern regime. These results suggest that knowledge of fine‐scale air‐sea heat flux gradients in late winter can potentially provide useful information about the NAO in weather forecasts and climate prediction systems.
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From Synoptic to Submesoscale: Understanding Sensible Heat Flux Variability in the Southern Ocean
Abstract Advances in uncrewed surface vehicles enable expanded observations in the critically undersampled Southern Ocean—a region vital for global heat uptake. Using data from three Saildrone missions that sampled the Pacific sector of the Southern Ocean in both summer and winter, we evaluate processes and spatiotemporal scales of decorrelation that drive sensible heat fluxes. Enhanced heat flux variability is primarily linked to synoptic‐scale southwesterly winds, with decorrelation scales of 50 km and 10 hr, consistent across seasons. These scales are influenced by both atmospheric forcing and oceanic variability, with sharp sea surface temperature changes occasionally driving pronounced shifts in sensible heat flux. Our results extend the observed relationship between wind direction and heat loss across the entire Pacific sector of the Southern Ocean, previously limited to three locations. Our data sets reveal over 8,000 temperature fronts ranging from <1 km to >20 km in width. These fine‐scale ocean processes contribute to the heat flux variability 35% of the time. While wind‐related variability dominates sensible heat flux changes across the smallest fronts, the ocean's role becomes increasingly significant with wider ocean fronts, particularly those over 4 km in width. However, due to their larger abundance, the total change of sensible heat flux over smaller (1 km) fronts is an order of magnitude greater than larger fronts (>4 km). These results highlight the role of fine‐scale atmosphere‐ocean interactions relating to heat flux variability in the Southern Ocean, offering valuable insights for enhancing flux estimates in this critical region.
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- Award ID(s):
- 1924388
- PAR ID:
- 10647721
- Publisher / Repository:
- AGU
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 130
- Issue:
- 10
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2024JC022292
