@article{fdi:010089596,
  title = {{R}ole of intersecting equatorial and coastal waveguides near {S}ri {L}anka on intraseasonal sea level variability along the west coast of {I}ndia},
  author = {{S}uresh, {I}. and {V}ialard, {J}{\'e}r{\^o}me and {I}zumo, {T}akeshi and {L}engaigne, {M}atthieu},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he sea level variations along the west coast of {I}ndia ({WCI}) significantly affect the ecosystems and fisheries, because of their tight coupling with the oxycline depths in this region, which hosts the world's largest natural hypoxic system. {H}ere, we investigate the main causes of the {WCI} sea level variability. {U}sing idealized experiments with a linear, continuously stratified ocean model, we first demonstrate that there is a direct pathway between the equatorial waveguide and the {WCI}, in addition to the well-documented pathway that aligns with the coastal waveguide in the {B}ay of {B}engal. {T}his direct connection results from the intersection of equatorial and coastal waveguides near {S}ri {L}anka. {T}he forced and reflected equatorial {R}ossby waves induce sea level variations at the {S}ri {L}ankan coast around 6 degrees {N}, which propagate directly to the {WCI} as coastal {K}elvin waves, without transiting through the {B}ay of {B}engal coastal waveguide. {U}sing model experiments with realistic coastline and forcing, we then illustrate that this direct pathway is the primary contributor (0.4 regression coefficient) to the {WCI} intraseasonal (20-150 days) sea level variability, followed by the {B}ay of {B}engal coastal waveguide pathway (0.3) and the wind forcing in a small region near {S}ri {L}anka (0.25). {T}he remote forcing originating from the rest of the {B}ay of {B}engal and the {WCI} local wind forcing have weaker influence. {W}e conclude by discussing why this direct connection exhibits strong impact on sea level variability at the intraseasonal timescale, while its influence is considerably weaker at the longer seasonal and interannual timescales. {S}ea level reflects variations in subsurface oceanic heat content and structure. {A}long the west coast of {I}ndia ({WCI}), it acts as a warning sign for sudden strong decrease in seawater oxygen content that has deleterious impacts on ecosystems and fisheries. {I}t is thus important to understand the causes of sea level variations in this region. {P}revious studies emphasized that equatorial wind variations force sea level anomalies that travel eastward, reach the {I}ndonesian coast, and then propagate counter clockwise around the {B}ay of {B}engal rim, around {S}ri {L}anka and to the {WCI}. {H}ere, we demonstrate that there is also a much shorter, direct pathway from the equatorial band to {S}ri {L}ankan coast and then to the {WCI}, bypassing the pathway through the {B}ay of {B}engal. {T}his newly discovered direct connection is in fact the primary contributor to {WCI} intraseasonal (20-150 days) sea level variations. {T}he "classical" {B}ay of {B}engal pathway is the second contributor. {W}e also identify a forcing "hotspot" over a small region east of {S}ri {L}anka as the third contributor. {F}inally, we demonstrate that the "direct" connection that we have highlighted here does not operate efficiently for sea level variations that span over a season or longer. {T}his study highlights a new pathway for propagation of signals from equatorial band directly to west coast of {I}ndia, bypassing {B}ay of {B}engal {T}his direct connection results from intersection of equatorial and coastal waveguides near {S}ri {L}anka {T}his pathway contributes to the west coast of {I}ndia sea level primarily at intraseasonal timescale, but weakly at longer timescales},
  keywords = {west coast of {I}ndia ; sea level variability ; equatorial waveguide ; coastal waveguide ; intraseasonal oscillations ; {N}orth {I}ndian {O}cean ; {OCEAN} {INDIEN} ; {INDE}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {O}ceans},
  volume = {129},
  numero = {3},
  pages = {e2023{JC}020198 [16 p.]},
  ISSN = {2169-9275},
  year = {2024},
  DOI = {10.1029/2023jc020198},
  URL = {https://www.documentation.ird.fr/hor/fdi:010089596},
}