GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Online Resource
    Online Resource
    Variability in the subtropical-tropical cells and its effect on near-surface temperature of the equatorial Pacific: a model study (2008)
    Associated volumes
    Details Availability
    In: Ocean science, Katlenburg-Lindau : Copernicus Publ., 2005, 4(2008), Seite 73-88, 1812-0792
    In: volume:4
    In: year:2008
    In: pages:73-88
    Description / Table of Contents: A set of experiments utilizing different implementations of the global ORCA-LIM model with horizontal resolutions of 2°, 0.5° and 0.25° is used to investigate tropical and extra-tropical influences on equatorial Pacific SST variability at interannual to decadal time scales. The model experiments use a bulk forcing methodology building on the global forcing data set for 1958 to 2000 developed by Large and Yeager (2004) that is based on a blend of atmospheric reanalysis data and satellite products. Whereas representation of the mean structure and transports of the (sub-)tropical Pacific current fields is much improved with the enhanced horizontal resolution, there is only little difference in the simulation of the interannual variability in the equatorial regime between the 0.5° and 0.25° model versions, with both solutions capturing the observed SST variability in the Nino3-region. The question of remotely forced oceanic contributions to the equatorial variability, in particular, the role of low-frequency changes in the transports of the Subtropical Cells (STCs), is addressed by a sequence of perturbation experiments using different combinations of fluxes. The solutions show the near-surface temperature variability to be governed by wind-driven changes in the Equatorial Undercurrent. The relative contributions of equatorial and off-equatorial atmospheric forcing differ between interannual and longer, (multi-) decadal timescales: for the latter there is a significant impact of changes in the equatorward transport of subtropical thermocline water associated with the lower branches of the STCs, related to variations in the off-equatorial trade winds. A conspicuous feature of the STC variability is that the equatorward transports in the interior and along the western boundary partially compensate each other at both decadal and interannual time scales, with the strongest transport extrema occurring during El Nino episodes. The behaviour is rationalized in terms of a wobbling in the poleward extents of the tropical gyres, which is manifested also in a meridional shifting of the bifurcation latitudes of the North and South Equatorial Current systems.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    Language: English
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    GEOMAR CATALOGUE
    Link to Library Catalog
    get availability status
  • 2
    facet.materialart.
    Unknown
    Southern Ocean wind stress affects the North Atlantic overturning via northward propagating temperature and salinity anomalies (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-08-02
    Description: The southern hemisphere westerly winds are projected to increase in the future, altering local ocean hydrography and dynamics. While anomalies of southern hemisphere origin were shown to affect the Atlantic Meridional Overturning Circulation, many details of this connection remain unexplained. Most existing studies are limited by the application of forced ocean models that prevent an atmospheric response to the anomalies, coarse resolution ocean models not able to explicitly simulate mesoscale variability, or a short runtime of experiments. Here we apply a coupled, nested model configuration covering the entire Atlantic at an eddying resolution of 1/10°, to study the inter-hemispheric propagation of anomalies generated by a 30% increase in southern hemisphere wind stress. To obtain statistically more robust results, a 5-member ensemble experiment is conducted with a runtime of 120 years of each member. The South Atlantic response is dominated by a sustained increase of Agulhas Leakage by 3 Sv. Based on a combination of Lagrangian and Eulerian analysis, we show that the propagation of anomalies generated by an increased inflow of Indian Ocean water into the South Atlantic, is a complicated interplay of advection, mixing and local atmospheric responses and thus not simply follows the advective pathways of the leakage water. The North Atlantic overturning responds with a strengthening of 1.5 Sv after approximately 80 years. Anomalous water mass transformation associated with the increased AMOC mainly occurs at the entry into the Nordic Seas, while enhanced sinking is seen along the boundary of the subpolar gyre.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    GFZ OAI
  • 3
    facet.materialart.
    Unknown
    Robust estimates for the decadal evolution of Agulhas leakage from the 1960s to the 2010s (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-01
    Description: Agulhas leakage, the transport of warm and salty waters from the Indian Ocean into the South Atlantic, represents a choke point for the surface branch of the global overturning circulation. Previous studies suggest that Agulhas leakage has been increasing under anthropogenic climate change as a response to strengthening Southern Hemisphere westerly winds, and that the resulting enhanced salt transport into the South Atlantic may counteract the projected weakening of the Atlantic meridional overturning circulation (AMOC) through warming and ice melting. However, due to its turbulent and intermittent nature, estimates for the past and future evolution of Agulhas leakage are sparse and individual estimates are associated with considerable uncertainties. Here we present an analysis of already established as well as new observation- and model-based estimates for Agulhas leakage variability to robustly quantify it’s (sub-)decadal evolution since the 1960s. We find that Agulhas leakage very likely increased in the 1960s through the 1980s, in agreement with strengthening Southern Hemisphere winds, while it appears unlikely that Agulhas leakage substantially increased since the 1990s, despite continuously strengthening winds. Our models further suggest that the increase in leakage coincided with a strengthening of the AMOC in the South Atlantic, which propagated into the North Atlantic within one to two decades. Hence, the South Atlantic may not only be important for future AMOC changes but may already have modulated basin-wide AMOC variability over the past decades. This underlines the importance of sustained efforts to monitor the AMOC in the South Atlantic, e.g., across the SAMBA array.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    GFZ OAI
  • 4
    facet.materialart.
    Unknown
    Identifying key regions for AMOC variability by explainable artificial intelligence (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-13
    Description: Machine Learning is fast becoming a crucial tool to process and investigate the big data of Ocean General Circulation Models (OGCM), and together with explanation methods it is possible to look into the decisions of learning methods, and thus understand dynamics. Even though monitoring arrays like RAPID or OSNAP are large international efforts, their limited sampling resolution still challenges the deciphering of AMOC variability into local vs. remote causes. Patterns that are correlated with these remote causes are of great interest for the community and are key for understanding the AMOC outside of monitoring arrays.To extract possible patterns and causes for the AMOC variability which can be later tested against single observations, we utilize OGCM data from the eddy-rich ocean model VIKING20X to train a Neural Network (NN). Its output is subsampled to mimic sparse observations (e.g., ARGO profiles), and explored to predict reconstructions of the complete fields and the AMOC strength of the model ‘truth’. By making the trained NNs interpretable with explainable artificial intelligence, we extract maps of interest that indicate which patterns are important for ocean dynamics and AMOC variability. To avoid a direct comparison between the model interpretations and the real world observations we aim for highly generalizable knowledge extracted from our NN.In conclusion, this study identifies the usefulness of applying NNs to aid the observational sampling strategy and the interpretation for AMOC monitoring.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    GFZ OAI
  • 5
    facet.materialart.
    Unknown
    Key roles for atmospheric feedback and mesoscale eddies in modelling the AMOC response to enhanced Greenland runoff (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-09-12
    Description: To understand and project the implications of enhanced Greenland Ice Sheet mass loss and potential Atlantic Meridional Overturning Circulation weakening it is necessary to determine and overcome challenges in simulating their complex linkages. We discuss the role of the ocean mean state, subpolar gyre circulation, mesoscale eddies and atmospheric coupling in shaping the response of the subpolar North Atlantic Ocean to enhanced Greenland runoff. A suite of eight dedicated 60 to 100-year long model experiments with and without atmospheric coupling, with eddy processes parameterized and explicitly simulated, and with regular and significantly enlarged Greenland runoff is presented. The important role of an interactive atmosphere stands out as being crucial for limiting the AMOC weakening because its response to ocean changes enables a compensating temperature feedback. Further, explicitly simulating mesoscale dynamics yields a more realistic distribution path of the meltwater along the North American coast and into the wider North Atlantic with implications for coastal sea-level rise projections. Underestimating eddy activity in the Labrador Sea may lead to too little or too slow entrainment of meltwater and lack of stratification in the deep convection regions. In this respect we demonstrate where eddy parameterization works quite successfully and where only high resolution (〉1/12˚) yields a realistic ocean response. This underlines the necessity to advance scale-aware eddy parameterizations for next-generation climate models.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    GFZ OAI
  • 6
    facet.materialart.
    Unknown
    North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part II: Inter-annual to decadal variability (2016)
    In:  EPIC3Ocean Modelling, 97, pp. 65-90
    Details
    Publication Date: 2016-02-29
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 7
    facet.materialart.
    Unknown
    An assessment of the Arctic Ocean in a suite of interannual CORE-II simulations. Part II: Liquid freshwater (2016)
    In:  EPIC3Ocean Modelling, 99, pp. 86-109
    Details
    Publication Date: 2018-06-07
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Format: application/pdf
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 8
    facet.materialart.
    Unknown
    Uptake and spreading of anthropogenic trace gases in an eddy-permitting model of the Atlantic Ocean (2007)
    In:  EPIC3Journal of Geophysical Research - Oceans, 112, C09017
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 9
    facet.materialart.
    Unknown
    Coordinated ocean-ice reference experiments (COREs) (2009)
    In:  EPIC3Ocean Modelling, 26(1), pp. 1-46
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 10
    facet.materialart.
    Unknown
    Oceanic Uptake of Anthropogenic Trace Gases - Effects of Mesoscale Processes in Ocean Models (2004)
    In:  EPIC3Ocean Sciences Meeting, Portland, USA.-30. Jan. 2004., 26
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER (OA)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...