My research is centered on polar ocean dynamics, with a recent focus on ice-ocean interactions from the mesoscale to microscale near and around ice shelf cavities and fjords in Greenland and Antarctica. Please also see the Movies link for simulations of the following work.
Completed Projects
(4) Linking Overturning, Recirculation, and Melt in Glacial Fjords
Glacial fjords are long, narrow, and deep inlets that connect glaciers to the open ocean. These glacial fjords exist around the margins of Greenland, West Antarctica, Alaska, and other regions, and collectively contribute a significant source of ice discharge into the ocean. Over the past two decades, tidewater glaciers in Greenland have accelerated, which can lead to sea level rise, and there is growing evidence that this acceleration is caused by deep warm water currents that flow into the fjords from the open ocean. These warm water currents have the potential to melt the submarine sides of glaciers, causing them to retreat over time. The dynamics of warm water delivery to the glacier face, particularly its interaction with fjord circulation, are presently poorly understood. In this study, we use high-resolution, process-oriented simulations to understand fjord currents and how they vary with different fjord characteristics and lead to different rates of submarine melting of the glacier face. We find that submarine glacial melt can cause feedbacks by amplifying the strength of the ocean currents, which further increase glacial melt. These results are an important step towards understanding a critical process that may help us improve sea level rise predictions.
(3) Dynamics of Eddies Generated by Sea Ice Leads
I co-supervised Kaylie Cohanim, who was an undergraduate researcher at UCLA. Kaylie used an idealized MITgcm configuration to study submesoscale eddy generation beneath sea ice leads.
(2) Geometric Constraints on Glacial Fjord-Shelf Exchange
The oceanic connections between tidewater glaciers and continental shelf waters are modulated and controlled by geometrically complex fjords. These fjords exhibit both overturning circulations and horizontal recirculations, driven by a combination of water mass transformation at the head of the fjord, variability on the continental shelf, and atmospheric forcing. However, it remains unclear which geometric and forcing parameters are the most important in exerting control on the overturning and horizontal recirculation. To address this, idealized numerical simulations are conducted using an isopycnal model of a fjord connected to a continental shelf, which is representative of regions in Greenland and the West Antarctic Peninsula. A range of sensitivity experiments demonstrate that sill height, wind direction/strength, subglacial discharge strength, and depth of offshore warm water are of first-order importance to the overturning circulation, while fjord width is also of leading importance to the horizontal recirculation. Dynamical predictions are developed and tested for the overturning circulation of the entire shelf-to-glacier-face domain, subdivided into three regions: the continental shelf extending from the open ocean to the fjord mouth, the sill overflow at the fjord mouth, and the plume-driven water mass transformation at the fjord head. A vorticity budget is also developed to predict the strength of the horizontal recirculation, which provides a scaling in terms of the overturning and bottom friction. Based on these theories, we may predict glacial melt rates that take into account overturning and recirculation, which may be used to refine estimates of ocean-driven melting of the Greenland and Antarctic ice sheets.
(1) Sill-Influenced Circulation in Ice Shelf Cavities
There are vast cavities forming beneath some of the fastest melting ice shelves in West Antarctica and northern Greenland. One notable example is the Pine Island Glacier in West Antarctica. The Pine Island Glacier has a tall bathymetric sill or “bump” in the seafloor that holds back relatively warm (by a few degrees) water from the open ocean. Our research seeks to understand how the height of the bump holds back open ocean, warm water from melting the glaciers in these regions.
The water within these ice shelf cavities are primarily made up of a warm, denser bottom layer that inflows into the cavities beneath ice shelves. The warm water then melts the glacier and flows out as colder water near the top. In observations, flow inside the cavity appears to have a distinctive two-layer structure, which is why we use a two-layer model to study these dynamics. We have found that most of the dynamics of this cavity flow depends on two parameters, the sill height and top/bottom surface friction (due to the water encountering and being slowed down by the rough seafloor and rough ice shelf face). Therefore, we can use these results to understand how sill height and seafloor friction control the melt rates at the undersides of many of the fastest melting glaciers in Antarctica and Greenland.
Ongoing Projects:
(8) Submesoscale Eddies beneath Antarctic sea ice
I am co-supervising Jennifer Kosty, who is an undergraduate researcher at UCLA. Jennifer is using seal and Argo data to find and analyze submesoscale eddies below sea ice around Antarctica.
(7) Roles of Geometry and Standing Eddies in Mediating Fjord-Shelf Exchange
Many of the idealized theories in projects (1),(2), and (4) above provide insight on fjord dynamics in cases with more realistic fjord geometries. However, there are additional features and nuances in fjord dynamics due to bathymetric complexity that are important for fjord dynamics and glacial melt rates..
(6) Energy Balance in the Shallow Water Equations
I am investigating the mean-eddy decomposition of the kinetic and potential energy balance relations in isopycnal coordinates. The differences between the energetics in isopycnal and z-coordinate systems are important to the interpretation of results using such models.
(5) Mechanisms of Barotropic Oceanic Zonal Jet Formation
Satellite altimetric observations and numerical simulations of the extra-tropical and mid-latitude oceans reveal the presence of weak zonal jets, embedded in a field of Rossby waves and mesoscale eddies. The precise mechanisms of jet formation, their interplay with waves and eddies — even their existence as distinct entities — remains a topic of debate. Here we revisit this problem through the lens of freely-evolving periodic shallow water quasi-geostrophic simulations, initialized with both wave and random-field initial conditions.
For a complete list of my research output, please refer to the
Publications page.
