|
|
|
|
|
| Lozier, M. Susan; Bacon, Sheldon; Bower, Amy S.; Cunningham, Stuart A.; De Jong, M. Femke; De Steur, Laura; Deyoung, Brad; Fischer, Juergen; Gary, Stefan F.; Greenan, Blair J. W.; Heimbach, Patrick; Holliday, Naomi P.; Houpert, Loic; Inall, Mark E.; Johns, William E.; Johnson, Helen L.; Karstensen, Johannes; Li, Feili; Lin, Xiaopei; Mackay, Neill; Marshall, David P.; Mercier, Herle; Myers, Paul G.; Pickart, Robert S.; Pillar, Helen R.; Straneo, Fiammetta; Thierry, Virginie; Weller, Robert A.; Williams, Richard G.; Wilson, Chris; Yang, Jiayan; Zhao, Jian; Zika, Jan D.. |
| A new ocean observing system has been launched in the North Atlantic in order to understand the linkage between the meridional overturning circulation and deep water formation. For decades oceanographers have understood the Atlantic Meridional Overturning Circulation (AMOC) to be primarily driven by changes in the production of deep water formation in the subpolar and subarctic North Atlantic. Indeed, current IPCC projections of an AMOC slowdown in the 21st century based on climate models are attributed to the inhibition of deep convection in the North Atlantic. However, observational evidence for this linkage has been elusive: there has been no clear demonstration of AMOC variability in response to changes in deep water formation. The motivation for... |
| Tipo: Text |
|
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00358/46881/46764.pdf |
| |
|
|
| Macgilchrist, Graeme A.; Johnson, Helen L.; Marshall, David P.; Lique, Camille; Thomas, Matthew; Jackson, Laura C.; Wood, Richard A.. |
| A substantial fraction of the deep ocean is ventilated in the high-latitude North Atlantic. Consequently, the region plays a crucial role in transient climate change through the uptake of carbon dioxide and heat. However, owing to the Lagrangian nature of the process, many aspects of deep Atlantic Ocean ventilation and its representation in climate simulations remain obscure. We investigate the nature of ventilation in the high latitude North Atlantic in an eddy-permitting numerical ocean circulation model using a comprehensive set of Lagrangian trajectory experiments. Backwards-in-time trajectories from a model-defined ‘North Atlantic DeepWater’ (NADW) reveal the locations of subduction from the surface mixed layer at high spatial resolution. The major... |
| Tipo: Text |
Palavras-chave: North Atlantic Ocean; Atmosphere-ocean interaction; Lagrangian circulation/transport; Ocean circulation; Boundary currents; Diapycnal mixing. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00646/75833/76825.pdf |
| |
|
|
| Hewitt, Helene T.; Roberts, Malcolm; Mathiot, Pierre; Biastoch, Arne; Blockley, Ed; Chassignet, Eric P.; Fox-kemper, Baylor; Hyder, Pat; Marshall, David P.; Popova, Ekaterina; Treguier, Anne-marie; Zanna, Laure; Yool, Andrew; Yu, Yongqiang; Beadling, Rebecca; Bell, Mike; Kuhlbrodt, Till; Arsouze, Thomas; Bellucci, Alessio; Castruccio, Fred; Gan, Bolan; Putrasahan, Dian; Roberts, Christopher D.; Van Roekel, Luke; Zhang, Qiuying. |
| Purpose of Review Assessment of the impact of ocean resolution in Earth System models on the mean state, variability, and future projections and discussion of prospects for improved parameterisations to represent the ocean mesoscale. Recent Findings The majority of centres participating in CMIP6 employ ocean components with resolutions of about 1 degree in their full Earth System models (eddy-parameterising models). In contrast, there are also models submitted to CMIP6 (both DECK and HighResMIP) that employ ocean components of approximately 1/4 degree and 1/10 degree (eddy-present and eddy-rich models). Evidence to date suggests that whether the ocean mesoscale is explicitly represented or parameterised affects not only the mean state of the ocean but also... |
| Tipo: Text |
Palavras-chave: Ocean models; Resolution; Parameterisation; Mesoscale; Submesoscale. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00654/76603/77753.pdf |
| |
|
|
| Macgilchrist, Graeme A.; Marshall, David P.; Johnson, Helen L.; Lique, Camille; Thomas, Matthew. |
| Ventilation of the upper ocean plays an important role in climate variability on interannual to decadal timescales by influencing the exchange of heat and carbon dioxide between the atmosphere and ocean. The turbulent nature of ocean circulation, manifest in a vigorous mesoscale eddy field, means that pathways of ventilation, once thought to be quasi-laminar, are in fact highly chaotic. We characterize the chaotic nature of ventilation pathways according to a nondimensional filamentation number, which estimates the reduction in filament width of a ventilated fluid parcel due to mesoscale strain. In the subtropical North Atlantic of an eddy-permitting ocean model, the filamentation number is large everywhere across three upper ocean density... |
| Tipo: Text |
Palavras-chave: Ventilation; North Atlantic; Thermocline; Chaos; Mesoscale eddies; Lagrangian trajectories. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00410/52104/52807.pdf |
| |
|
|
| Cimoli, Laura; Caulfield, Colm‐cille P.; Johnson, Helen L.; Marshall, David P.; Mashayek, Ali; Naveira Garabato, Alberto C.; Vic, Clement. |
| There have been recent advancements in the quantification of parameters describing the proportion of internal tide energy being dissipated locally and the “efficiency” of diapycnal mixing, i.e. the ratio of the diapycnal mixing rate to the kinetic energy dissipation rate. We show that oceanic tidal mixing is non‐trivially sensitive to the co‐variation of these parameters. Varying these parameters one at the time can lead to significant errors in the patterns of diapycnal mixing driven upwelling and downwelling, and to the over and under estimation of mixing in such a way that the net rate of globally‐integrated deep circulation appears reasonable. However, the local rates of upwelling and downwelling in the deep ocean are significantly different when both... |
| Tipo: Text |
|
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00595/70675/68873.pdf |
| |
|
|
|
