Research Interests:
Ocean circulation, Meridional Overturning Circulation, near-inertial waves, mixed layer dynamics, upper ocean energy budget, mesoscale eddies, satellite oceanography, statistical data analysis, machine learning, observational techniques and instrumentation
Role of Rossby Waves and Eddies to the interannual variability of the Brazil Current
(Collaborators: Marlos Goes, Rick Lumpkin, Paolo Polito, Claudia Schmid, Hosmay Lopez)
The role of the propagating modes of variability in modulating the western boundary current is investigated in the South Atlantic Ocean using a complex empirical orthogonal function (EOF) analysis of satellite-derived sea surface heights between 1993 and 2017. It is found that the inter-annual variability of the volume transport of the western boundary current is influenced greatly by the westward propagating Rossby-like waves from the African Coast.
The recent changes in the ENSO regime in the Pacific Ocean are also found to be related to the inter-annual variability via atmospheric teleconnections. (Majumder et. al 2019)
Ocean circulation, Meridional Overturning Circulation, near-inertial waves, mixed layer dynamics, upper ocean energy budget, mesoscale eddies, satellite oceanography, statistical data analysis, machine learning, observational techniques and instrumentation
Role of Rossby Waves and Eddies to the interannual variability of the Brazil Current
(Collaborators: Marlos Goes, Rick Lumpkin, Paolo Polito, Claudia Schmid, Hosmay Lopez)
The role of the propagating modes of variability in modulating the western boundary current is investigated in the South Atlantic Ocean using a complex empirical orthogonal function (EOF) analysis of satellite-derived sea surface heights between 1993 and 2017. It is found that the inter-annual variability of the volume transport of the western boundary current is influenced greatly by the westward propagating Rossby-like waves from the African Coast.
The recent changes in the ENSO regime in the Pacific Ocean are also found to be related to the inter-annual variability via atmospheric teleconnections. (Majumder et. al 2019)
Variability of the Benguela Current between 1993 and 2015(Collaborator: Claudia Schmid)
A three dimensional velocity product (Argo & Altimetry) using observations from Argo floats and satellite altimetry is used to understand the variability of the Benguela Current between 1993 and 2015. This new data set enable us to present a detailed analysis of the variability of the meridional transport of this current, which was not possible previously. Results show that the mean meridional transport in the upper 800 m between the continental shelf of Africa and 3° E, decreases from 23 ± 3 Sv at 31° S to 11 ± 3 Sv at 28° S. The Agulhas eddies from the Indian Ocean plays a major role in modulating the transport of this current at the southern latitudes; no such influence is seen north of 30°S. (relevant publication) Meridional Overturning Ciruclation (MOC) in the South Atlantic(Collaborators: Claudia Schmid, George Halliwell, Marlos Goes, Gustavo Goni, Shenfu Dong)
The three dimensional absolute velocity product described above is used to understand the variability of the MOC at four different latitudes (20°S, 25°S, 30°S and 35°S) in the South Atlantic between 2000 and 2014. The details of this work was published in majumder_et_al_2016. In an ongoing effort, heat and fresh water budgets in the South Atlantic ocean are estimated to identify the processes that govern the variability of the meridional heat (MHT) and freshwater transports (MOV). |
Climatology of geostrophic velocity (cm/sec) of the Benguela Current. The details of the velocity product can be found here
Seasonality of MOC using Argo & Altimetry (black), SODA (green), NCEP/GODAS (blue) and HYCOM (red).
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Near Inertial Waves and Mixed layer Energy Budgets(Collaborators: Amit Tandon, Tom Farrar, Daniel Rudnick)
Data from a mooring array in the Arabian Sea is used to understand the growth and decay of near-inertial currents in the upper ocean during the northeast and the southwest monsoons in the Arabian Sea. Monsoon winds in this part of the world ocean are characterized by steady, unidirectional wind stress. To understand the upper ocean response during these two different wind periods, kinetic energy budgets in the mixed layer and in the transition layer are analyzed at near-inertial frequencies. In addition to this, how the vertical shear in the transition layer evolves at near-inertial frequencies is explained. It is shown that even though the winds in the Arabian Sea is unidirectional strong near-inertial currents are excited in the upper ocean due to fluctuation in amplitude of the wind stress. A fraction of the near-inertial wind energy propagates down the transition layer into the interior ocean during strong near-inertial events. A mixed layer model was used for the interpretation. The details of this research can be found at majumder_et_al_2015. |
Wind stress (first panel), near-inertial kinetic energy in the mixed layer and the transition layer and the residual flux (second panel). Near-inertial currents and the downward flux of near-inertial energy (3rd and the 4th panel).
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Eddy driven mixing and the role of near-inertial currents in the SST evolution in the South Eastern Pacific Region
(Collaborators: Robert Weller, Amit Tandon) The importance of diurnal restratification events and near-inertial currents in the evolution of sea surface temperature in the Southeastern Pacific is investigated using observations from a long-term mooring. In addition to this, the roles of mesoscale and submesoscale eddies in the upper ocean's temperature and salinity distribution are also analysed. Observations used in this research is from a long-term mooring (STRATUS) off the Peru-Chile coast at about 20 ° S, 85 ° W. A mixed-layer model was used for the interpretation. A part of this work that focuses on the role of near-inertial waves in setting up the sea surface temperature was published in Weller_et_al_2014. The part on the role of eddies is in preparation. |
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