Variability of Large-scale Ocean Circulation and Meridional Heat Transport in the Atlantic Ocean

• Main Author: Zhang, Jinting
• Other Authors: Thompson, LuAnne
• Format: Thesis
• Language: English
• Published: 2015
• Subjects: meridional heat transport; meridional overturning circulation; ocean circulation; Physical oceanography; oceanography; Greenland
• Online Access: http://hdl.handle.net/1773/34107

Thesis (Ph.D.)--University of Washington, 2015 The research described in the dissertation addresses what controls the variability of ocean circulation and meridional heat transport (MHT) in the Atlantic Ocean on different timescales. Chapter 2 focuses on the contribution of surface heating and wind forcing with/without topography to the seasonal and interannual-to-decadal variations of large-scale sea surface height (SSH) using simplified models. On the seasonal timescale thermosteric height explains most of the SSH variance north of 18°N and first mode linear long Rossby wave explains the SSH between 10°N-15°N and east of Greenland. On interannual-to-decadal timescales, a topographic Sverdrup response explains interannual-to-decadal SSH between 53°N and 63°N east of Greenland, suggesting the important role of topography in the subpolar region. Farther south, the linear Rossby wave model explains SSH variations on interannual-to-decadal timescales between 30°N and 50°N from mid-basin to the eastern boundary. In Chapter 3, perturbation experiments and a 1000-year control simulation in the GFDL coupled model CM2.1 are used to investigate the evolution of the Atlantic meridional overturning circulation (AMOC) and its related upper ocean heat content (UOHC) on the decadal timescale. A slow southward propagation of positive AMOC anomaly in northern high latitudes leads to a convergence (divergence) of the Atlantic MHT anomaly in the subpolar (Gulf Stream) region, thus warming (cooling) in the subpolar (Gulf Stream) region after several years. The study presented in Chapter 4 examines the coherence structure of the interannual MHT variability in the Atlantic tropics and subtropics using seven simulations in the CMIP5 (Coupled Model Intercomparison Project Phase 5) archive as well as a hindcast simulation in the isopycnal ocean model GOLD (Generalized Ocean Layered Dynamics) from 1971 to 2009. The spatial pattern for the leading mode of the interannual MHT anomaly from all the model simulations has the same sign from ...