@article {goldsworth_destratifying_2024,
	title = {Destratifying and Restratifying Instabilities During Down-Front Wind Events: A Case Study in the Irminger Sea},
	journal = {Journal of Geophysical Research: Oceans},
	volume = {129},
	number = {2},
	year = {2024},
	note = {_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2023JC020365},
	pages = {e2023JC020365},
	abstract = {Observations indicate that symmetric instability is active in the East Greenland Current during strong northerly wind events. Theoretical considerations suggest that mesoscale baroclinic instability may also be enhanced during these events. An ensemble of idealized numerical ocean models forced with northerly winds shows that the short time-scale response (from 10 days to 3 weeks) to the increased baroclinicity of the flow is the excitation of symmetric instability, which sets the potential vorticity of the flow to zero. The high latitude of the current means that the zero potential vorticity state has low stratification, and symmetric instability destratifies the water column. On longer time scales (greater than 4 weeks), baroclinic instability is excited and the associated slumping of isopycnals restratifies the water column. Eddy-resolving models that fail to resolve the submesoscale should consider using submesoscale parameterizations to prevent the formation of overly stratified frontal systems following down-front wind events. The mixed layer in the current deepens at a rate proportional to the square root of the time-integrated wind stress. Peak water mass transformation rates vary linearly with the time-integrated wind stress. Mixing rates saturate at high wind stresses during wind events of a fixed duration which means increasing the peak wind stress in an event leads to no extra mixing. Using ERA5 reanalysis data we estimate that between 0.9 Sv and 1.0 Sv of East Greenland Coastal Current Waters are produced by mixing with lighter surface waters during wintertime due to down-front wind events. Similar amounts of East Greenland-Irminger Current water are produced.},
	keywords = {Atlantic Meridional Overturning Circulation, East Greenland Current, mixing, sub-polar North Atlantic, symmetric instability, water mass transformation},
	issn = {2169-9291},
	doi = {10.1029/2023JC020365},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023JC020365},
	author = {Goldsworth, F. W. and Johnson, H. L. and Marshall, D. P. and Le Bras, I. A.}
}
@article {buckley_buoyancy_2023,
	title = {Buoyancy forcing and the subpolar Atlantic meridional overturning circulation},
	journal = {Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences},
	volume = {381},
	number = {2262},
	year = {2023},
	note = {Publisher: Royal Society},
	month = {oct},
	pages = {20220181},
	abstract = {The North Atlantic meridional overturning circulation and its variability are examined in terms of the overturning in density space and diapycnal water mass transformation. The magnitude of the mean overturning is similar to the surface water mass transformation, but the density and properties of these waters are modified by diapycnal mixing. Surface waters are progressively densified while circulating cyclonically around the subpolar gyre, with the densest waters and deepest convection occurring in the Labrador Sea and Nordic Seas. The eddy-driven interaction between the convective interior and boundary currents is a key to the export of dense waters from marginal seas. Due to the multitude of pathways of dense waters within the subpolar gyre, as well as mixing with older waters, waters exiting the subpolar gyre have a wide range of ages, with a mean age on the order of a decade. As a result, interannual changes in water mass transformation are mostly balanced locally and do not result in changes in export to the subtropics. Only persistent changes in water mass transformation result in changes in export to the subtropics. The dilution of signals from upstream water mass transformation suggests that variability in export of dense waters to the subtropics may be controlled by other processes, including interaction of dense waters with the energetic upper ocean. This article is part of a discussion meeting issue {\textquoteleft}Atlantic overturning: new observations and challenges{\textquoteright}.},
	keywords = {Atlantic Meridional Overturning Circulation, buoyancy forcing, water mass transformation},
	doi = {10.1098/rsta.2022.0181},
	url = {https://royalsocietypublishing.org/doi/10.1098/rsta.2022.0181},
	author = {Buckley, Martha W. and Lozier, M. Susan and Desbruy{\`e}res, Damien and Evans, Dafydd Gwyn}
}
@article {chafik_observed_2023,
	title = {Observed mechanisms activating the recent subpolar North Atlantic Warming since 2016},
	journal = {Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences},
	volume = {381},
	number = {2262},
	year = {2023},
	note = {Publisher: Royal Society},
	month = {oct},
	pages = {20220183},
	abstract = {The overturning circulation of the subpolar North Atlantic (SPNA) plays a fundamental role in Earth{\textquoteright}s climate variability and change. Here, we show from observations that the recent warming period since about 2016 in the eastern SPNA involves increased western boundary density at the intergyre boundary, likely due to enhanced buoyancy forcing as a response to the strong increase in the North Atlantic Oscillation since the early 2010s. As these deep positive density anomalies spread southward along the western boundary, they enhance the North Atlantic Current and associated meridional heat transport at the intergyre region, leading to increased influx of subtropical heat into the eastern SPNA. Based on the timing of this chain of events, we conclude that this recent warming phase since about 2016 is primarily associated with this observed mechanism of changes in deep western boundary density, an essential element in these interactions. This article is part of a discussion meeting issue {\textquoteleft}Atlantic overturning: new observations and challenges{\textquoteright}.},
	keywords = {Atlantic Meridional Overturning Circulation},
	doi = {10.1098/rsta.2022.0183},
	url = {https://royalsocietypublishing.org/doi/10.1098/rsta.2022.0183},
	author = {Chafik, L{\'e}on and Penny Holliday, N. and Bacon, Sheldon and Baker, Jonathan A. and Desbruy{\`e}res, Damien and Frajka-Williams, Eleanor and Jackson, Laura C.}
}
@article {kostov_fast_2022,
	title = {Fast mechanisms linking the Labrador Sea with subtropical Atlantic overturning},
	journal = {Climate Dynamics},
	year = {2022},
	month = {aug},
	abstract = {We use an ocean general circulation model and its adjoint to analyze the causal chain linking sea surface buoyancy anomalies in the Labrador Sea to variability in the deep branch of the Atlantic meridional overturning circulation (AMOC) on inter-annual timescales. Our study highlights the importance of the North Atlantic Current (NAC) for the north-to-south connectivity in the AMOC and for the meridional transport of Lower North Atlantic Deep Water (LNADW). We identify two mechanisms that allow the Labrador Sea to impact velocities in the LNADW layer. The first mechanism involves a passive advection of surface buoyancy anomalies from the Labrador Sea towards the eastern subpolar gyre by the background NAC. The second mechanism plays a dominant role and involves a dynamical response of the NAC to surface density anomalies originating in the Labrador Sea; the NAC adjustment modifies the northward transport of salt and heat and exerts a strong positive feedback, amplifying the upper ocean buoyancy anomalies. The two mechanisms spin up/down the subpolar gyre on a timescale of years, while boundary trapped waves rapidly communicate this signal to the subtropics and trigger an adjustment of LNADW transport on a timescale of months. The NAC and the eastern subpolar gyre play an essential role in both mechanisms linking the Labrador Sea with LNADW transport variability and the subtropical AMOC. We thus reconcile two apparently contradictory paradigms about AMOC connectivity: (1) Labrador Sea buoyancy anomalies drive AMOC variability; (2) water mass transformation is largest in the eastern subpolar gyre.},
	keywords = {AMOC, Atlantic Meridional Overturning Circulation, Labrador Sea, LNADW, Lower North Atlantic Deep Water, NAC, North Atlantic Current, OSNAP, RAPID-MOCHA, Surface heat fluxes, water mass transformation},
	issn = {1432-0894},
	doi = {10.1007/s00382-022-06459-y},
	url = {https://doi.org/10.1007/s00382-022-06459-y},
	author = {Kostov, Yavor and Messias, Marie-Jos{\'e} and Mercier, Herl{\'e} and Johnson, Helen L. and Marshall, David P.}
}
