The Role of Sea Ice in Polar Climate Change: Investigating Distinct Cause-Effect Relationships in Each Hemisphere

• Main Author: Kaufman, Zachary Snow
• Other Authors: Feldl, Nicole
• Format: Thesis
• Language: English
• Published: eScholarship, University of California 2022
• Subjects: Atmospheric sciences; Climate change; Physical oceanography; Causal Inference; Climate Variability; Model Projections; Polar Regions; Predictability; Sea Ice; Antarc*; Antarctic; ice pack; Sea ice; Southern Ocean
• Online Access: https://escholarship.org/uc/item/8159t0x5; https://escholarship.org/content/qt8159t0x5/qt8159t0x5.pdf

Earth’s poles are uniquely sensitive to climate system perturbations; in recent decades, Arctic temperatures have warmed at twice the global average. Antarctic warming has been slower to emerge, but climate models project long-term changes in both polar regions, posing severe consequences for societies, ecosystems, and global weather patterns. Managing these consequences necessitates a detailed physical understanding of sea ice and its central role in governing the high-latitude energy budget. To address this need, my thesis investigates ice-ocean-atmosphere interactions in the polar regions. I quantify causal relationships among the physical processes shaping high-latitude climate, characterizing how sea ice both drives and responds to climate variability and change in each hemisphere. The results of my research provide physical insights towards more accurate climate models and guide future observations in these remote, data-sparse regions.In Chapter Two (Kaufman et al. 2020) I study the relationship between Southern Ocean polynyas and high-latitude climate variability. These anomalous ice-free ocean regions, enclosed by the winter sea-ice pack, have been observed to occasionally release heat from the deep ocean to the overlying atmosphere. Yet, most standard resolution climate models represent these features poorly. I analyzed output from a fully coupled model that effectively simulates polynyas due to its uniquely high-resolution seafloor bathymetry. I found that the reduction of surface heat fluxes during periods of full ice cover is not fully compensated by poleward heat transport. This imbalance increases ocean heat content, supplies polynya heat loss, and drives higher atmospheric temperatures. The results disentangle the complex processes that both enable polynyas’ existence and respond to them, providing a robust physical description of these rare, but impactful, events. This research was conducted in collaboration with the Climate, Ocean, and Sea Ice Modeling (COSIM) group at Los Alamos National ...