Talks

The principle dynamical components in the large scale ocean (i.e. spatial scales larger than O(100m)) are dominated by mesoscale eddies, submesoscale currents and interia gravity waves comprising both storm-forced Near-Inertial Waves (NIWs) and tidally generated internal waves (TIWs).  While mesoscale eddies (length scales of 10s of kms), generated primarily through baroclinic instability are the principal reservoir of kinetic energy in the world oceans, submesoscale currents (O(1-10 km)) comprising mixed layer eddies and fronts interact strongly with mesoscales and are critical for  regulating biogeochemical and air-sea fluxes. Here we use the so-called coarse-graining approach to compute cross-scale energy fluxes that shed light on dynamical interactions between these three components and their impact on the upper ocean. By first decomposing the oceanic velocity field into rotational and divergent components on one hand (i.e. a Helmholtz decomposition) and separately using an eddy-IG...

Mesoscale Eddies are rotating structures found in the ocean with size of 50 to 500 km with a lifespan of 10 to 100 days. Eddies can be detected from Sea Surface Height (SSH) data. These circulations play a major role in transportation of heat, salt, carbon and nutrients throughout the ocean and are also associated with complex atmosphere-ocean interactions. That is why the detection of the eddies is extremely important to understand the big picture of the climate. Various, physics based methods were used for eddies detection but dependent upon the threshold values and human expertise which leads to the false detection. Therefore, advance techniques of artificial intelligence are needed to overcome these challenges. Various Deep Learning based works were done over the South China Sea and South Atlantic Ocean but Bay of Bengal is less explored. In this study we trained deep learning models, U-Net and Attention U-Net, for detecting the mesoscale ocean eddies over Bay of Bengal from daily ...

Present-day galaxies still contain a multitude of clues about their formation histories. But which properties should we best look at and what do they actually reveal about the past? Using cosmological simulations, I will show what insights about a galaxy's formation and merger history can be gained from a diverse set of measurements. For this, I will show how the overall galaxy shapes and tidal features in the outskirts are related to the inner kinematics. These results give us indications about the correlation with the recent merger histories of the galaxies. Finally, I will discuss how early gas-rich mergers can be revealed through the ages of globular cluster populations.

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Hilbert spaces are incomprehensibly vast and rich. Model Hamiltonians are space ships. They could take us to new worlds, such as cold \textit{spin liquid oasis} in hot regions in Hilbert space deserts. Exact decomposition of isotropic Heisenberg Hamiltonian on a Honeycomb lattice into a sum of 3 non-commuting (permuted) Kitaev Hamiltonians, helps us build a degenerate \textit{manifold of metastable flux free Kitaev spin liquid vacua} and vector Fermionic (Goldstone like) collective modes. Our method, \textit{symmetric decomposition of Hamiltonians}, will help design exotic metastable quantum scars and exotic quasi particles, in nonexotic real systems.
G. Baskaran, arXiv:2309.07119

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We use the ocean-only global circulation model (gcm) ICON-O with very high horizontal (5km), vertical and temporal resolution including the astronomical tidal forcing to study the effects of mesoscale eddies on the low-mode internal tide. This is the first study using a high-resolution gcm to study these interactions.
The diagnosed lunar semidiurnal (M2) internal tide reveals wavy patterns with horizontally varying wavelengths, which do not correspond to plain waves.
We therefore propose a new modal decomposition method based on spatial empirical orthogonal functions. Using this method we observe enhanced dissipation of the internal tide kinetic energy inside and in the lee area of the eddy, which can be attributed to enhanced weakening of the low mode internal tide. We also observe that eddies can significantly alter the propagation pathways of the low-mode internal tide by refracting the beam southwards.
We also find that the high-modes of the internal tide are trapped inside and ...

Baroclinic instability is a phenomenon in rotating stratified systems, and is known to play an important role in the Earth's atmosphere and ocean. The Eady problem is a text book example of baroclinic instability widely invoked for various applications (along with the Charney and Phillips problem). In the first part we recap some of the features of the standard geostrophic Eady problem (e.g., as described in most standard GFD textbooks), such as the linear instability characteristics, method of solution by analytical means, instability mechanism in terms of Counter-propagating Rossby Waves (CRWs), relations to baroclinic lifecycles, and its parameterisation in atmospheric and/or oceanic systems (e.g., works of Green, Gent-McWilliams and/or Greatbach-Lamb schemes). In the second part, we proceed to highlight and/or clarify some features of a modified Eady linear instability problem in the presence of a slope, namely (i) links of the Eady problem with quantum mechanics under the umbrella...