Dynamics of Ocean Circulation in Glacial Fjords and Ice-Shelf Cavities

Download or read book Dynamics of Ocean Circulation in Glacial Fjords and Ice-Shelf Cavities written by Ken Zhao and published by . This book was released on 2021 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: Melting at the submerged faces of marine-terminating glaciers at the fringes of Antarcticaand Greenland has increased dramatically in recent decades. This acceleration has been driven in part by the ocean circulation within ice-shelf cavities and fjords through the increased access of warm, salty water masses and a presumed amplification of the heat flux towards these glaciers. However, the dynamics of the ocean circulation within fjords and ice-shelf cavities are poorly understood and require the representation of scales of motion that range seven orders of magnitude, from 100s of kilometers (circulation on the adjacent coastal shelves) down to centimeters (at the ice-ocean inner boundary layer interface). This presents unique challenges for existing models, which underpredict melt rates by an order of magnitude compared to recent observations at vertical glacial faces. The work in this dissertation seeks to improve the agreement of models and theory with observations and provide a better understanding of the dynamical processes within fjords and ice-shelf cavities. To accomplish this, a series of high-resolution numerical simulations of increasing complexity is presented. In Chapters 2 and 3, 2- and 3-layer isopycnal model configurations with idealized geometry and forcing are used; subsequently in Chapters 4 and 5, z-coordinate models with idealized and semi-realistic regional configurations are used. Inspired by the simplest models, theories of the overturning and horizontal recirculation (the two primary bulk measures of circulation strength within fjords and ice-shelf cavities,) are developed and tested and used to make predictions for the glacial melt rate. These theories are then tested in increasingly complex models, which reveal new features and factors that also should be taken into account. Three important features presented in this dissertation include the identification of cavity/fjord geometry as a critical constraint on heat transport, melt-circulation feedbacks in fjords, and the existence of standing eddies, which can both further amplify glacial melt rates. This work advances the understanding of the dynamics within fjords and ice-shelf cavities and many promising avenues of future work have emerged as a result. Future work will likely continue to provide critical improvements to our understanding of ocean circulation near the margins of ice sheets and improve our projections of future sea level rise and glacial retreat in a changing climate.