@article {petit_propagation_2023,
	title = {Propagation and Transformation of Upper North Atlantic Deep Water From the Subpolar Gyre to 26.5{\textdegree}N},
	journal = {Journal of Geophysical Research: Oceans},
	volume = {128},
	number = {8},
	year = {2023},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023JC019726},
	pages = {e2023JC019726},
	abstract = {Because new observations have revealed that the Labrador Sea is not the primary source for waters in the lower limb of the Atlantic Meridional Overturning Circulation (AMOC) during the Overturning in the Subpolar North Atlantic Programme (OSNAP) period, it seems timely to re-examine the traditional interpretation of pathways and property variability for the AMOC lower limb from the subpolar gyre to 26.5{\textdegree}N. In order to better understand these connections, Lagrangian experiments were conducted within an eddy-rich ocean model to track upper North Atlantic Deep Water (uNADW), defined by density, between the OSNAP line and 26.5{\textdegree}N as well as within the Labrador Sea. The experiments reveal that 77\% of uNADW at 26.5{\textdegree}N is directly advected from the OSNAP West section along the boundary current and interior pathways west of the Mid-Atlantic Ridge. More precisely, the Labrador Sea is a main gateway for uNADW sourced from the Irminger Sea, while particles connecting OSNAP East to 26.5{\textdegree}N are exclusively advected from the Iceland Basin and Rockall Trough along the eastern flank of the Mid-Atlantic Ridge. Although the pathways between OSNAP West and 26.5{\textdegree}N are only associated with a net formation of 1.1 Sv into the uNADW layer, they show large density changes within the layer. Similarly, as the particles transit through the Labrador Sea, they undergo substantial freshening and cooling that contributes to further densification within the uNADW layer.},
	issn = {2169-9291},
	doi = {10.1029/2023JC019726},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023JC019726},
	author = {Petit, T. and Lozier, M. S. and R{\"u}hs, S. and Handmann, P. and Biastoch, A.}
}
@article {petit_understanding_2023,
	title = {Understanding the Sensitivity of the North Atlantic Subpolar Overturning in Different Resolution Versions of HadGEM3-GC3.1},
	journal = {Journal of Geophysical Research: Oceans},
	volume = {128},
	number = {10},
	year = {2023},
	note = {_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2023JC019672},
	pages = {e2023JC019672},
	abstract = {The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the global climate but is not simulated consistently across models or model resolutions. Here, we use a hierarchy of the global coupled model HadGEM3-GC3.1, with ocean resolutions of 1{\textdegree}, {\textonequarter}{\textdegree}, and 1/12{\textdegree}, to evaluate the subpolar AMOC and its sensitivity to horizontal resolution. In line with observations, the models show that the mean overturning and surface forced water mass transformation (SFWMT) are concentrated in the eastern subpolar gyre rather than in the Labrador Sea. However, the magnitude of the overturning along the OSNAP line at medium and high resolutions is 25\% and 40\% larger than in the observations, respectively. This disagreement in overturning strength is noted for both OSNAP East and OSNAP West, and is mainly due to anomalously large SFWMT rather than anomalously large interior mixing or overflow transport from the Nordic Seas. Over the Labrador Sea, the intensification of SFWMT with resolution is explained by a combination of two main biases. Anomalously warm surface water enhances heat loss and reduces the extension of marginal sea ice, which increases the surface density flux over the boundary of the basin. A bias in salinity leads to anomalously dense surface water that shifts the outcropping area of the AMOC isopycnal and results in intense dense water formation along the boundary of the basin at medium and high resolutions. Thus, our analysis sheds light on a range of model biases responsible for large overturning over the Labrador Sea in climate models.},
	issn = {2169-9291},
	doi = {10.1029/2023JC019672},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023JC019672},
	author = {Petit, T. and Robson, J. and Ferreira, D. and Jackson, L. C.}
}
@article {jackson_north_2022,
	title = {North Atlantic overturning and water mass transformation in CMIP6 models},
	journal = {Climate Dynamics},
	year = {2022},
	abstract = {Climate models are important tools for investigating how the climate might change in the future, however recent observations have suggested that these models are unable to capture the overturning in subpolar North Atlantic correctly, casting doubt on their projections of the Atlantic Meridional Overturning Circulation (AMOC). Here we compare the overturning and surface water mass transformation in a set of CMIP6 models with observational estimates. There is generally a good agreement, particularly in the recent conclusion from observations that the mean overturning in the east (particularly in the Iceland and Irminger seas) is stronger than that in the Labrador Sea. The overturning in the Labrador Sea is mostly found to be small, but has a strong relationship with salinity: fresh models have weak overturning and saline models have stronger mean overturning and stronger relationships of the Labrador Sea overturning variability with the AMOC further south.We also find that the overturning reconstructed from surface flux driven water mass transformation is a good indicator of the actual overturning, though mixing can modify variability and shift signals to different density classes.},
	keywords = {AMOC, CMIP6},
	issn = {1432-0894},
	doi = {10.1007/s00382-022-06448-1},
	url = {https://doi.org/10.1007/s00382-022-06448-1},
	author = {Jackson, L. C. and Petit, T.}
}
@article {RN246,
	title = {Subpolar North Atlantic western boundary density anomalies and the Meridional Overturning Circulation},
	journal = {Nature Communications},
	volume = {12},
	number = {1},
	year = {2021},
	pages = {3002},
	type = {Journal Article},
	abstract = {Changes in the Atlantic Meridional Overturning Circulation, which have the potential to drive societally-important climate impacts, have traditionally been linked to the strength of deep water formation in the subpolar North Atlantic. Yet there is neither clear observational evidence nor agreement among models about how changes in deep water formation influence overturning. Here, we use data from a trans-basin mooring array (OSNAP{\textemdash}Overturning in the Subpolar North Atlantic Program) to show that winter convection during 2014{\textendash}2018 in the interior basin had minimal impact on density changes in the deep western boundary currents in the subpolar basins. Contrary to previous modeling studies, we find no discernable relationship between western boundary changes and subpolar overturning variability over the observational time scales. Our results require a reconsideration of the notion of deep western boundary changes representing overturning characteristics, with implications for constraining the source of overturning variability within and downstream of the subpolar region.},
	doi = {10.1038/s41467-021-23350-2},
	url = {https://app.dimensions.ai/details/publication/pub.1138293382 https://www.nature.com/articles/s41467-021-23350-2.pdf},
	author = {Li, F. and Lozier, M. S. and Bacon, S. and Bower, A. S. and Cunningham, S. A. and de Jong, M. F. and deYoung, B. and Fraser, N. and Fried, N. and Han, G. and Holliday, N. P. and Holte, J. and Houpert, L. and Inall, M. E. and Johns, W. E. and Jones, S. and Johnson, C. and Karstensen, J. and Le Bras, I. A. and Lherminier, P. and Lin, X. and Mercier, H. and Oltmanns, M. and Pacini, A. and Petit, T. and Pickart, R. S. and Rayner, D. and Straneo, F. and Thierry, V. and Visbeck, M. and Yashayaev, I. and Zhou, C.}
}
