Investigating the Causes of Arctic Amplification: Interactions of the Atmosphere and Ocean
Open Access
- Author:
- Sanchez, Julie M
- Graduate Program:
- Geography
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 05, 2022
- Committee Members:
- Sukyoung Lee, Outside Unit & Field Member
Guido Cervone, Major Field Member
Andrew Carleton, Chair & Dissertation Advisor
Brian King, Program Head/Chair
Luke Trusel, Major Field Member - Keywords:
- Arctic Amplification
local forcing
remote forcing - Abstract:
- Observations and model simulations have shown the Arctic to be warming the fastest when compared to the rest of the world, a phenomenon known as Arctic Amplification (AA). The Arctic sea ice extent has decreased in every month and season since 1979. There is not yet a definitive “cause” for this downward trend in the Arctic, but a number of studies conclude opposing processes likely are involved, such as sea ice-albedo feedback and horizontal moisture and heat transports. In this dissertation, I examine the associations between AA and physical mechanisms, particularly the moisture flux convergence, surface air temperature, surface skin temperature, and variables from the surface energy budget (i.e., turbulent heat fluxes, solar radiation, and downward IR). I use a combination of observation and reanalysis-based approaches, specifically for the Greenland Ice Sheet (GrIS) due to increased surface melt in recent years. I use the ECMWF Reanalysis (ERA-Interim) to investigate the GrIS surface energy balance to determine what portion of the ice-sheet surface skin temperature increase over the 1979 to 2016 period can be attributed to the downward longwave and solar radiation, latent and sensible heat fluxes, and residual conduction. I show a dominance by the downward longwave radiation in all months and seasons, which is an important contributor to surface melt on the GrIS. I then analyze the surface observation dataset Programme for Monitoring of the Greenland Ice Sheet (PROMICE; Ashlstrøm & PROMICE project team 2008) to determine how surface air temperature and other climate variables (e.g., latent and sensible heat fluxes, downward IR, shortwave radiation, surface pressure) are significantly related. Using data from the PROMICE stations allows the investigation of the physical mechanisms at a smaller geographic scale on the GrIS. Multiple variables were shown to be statistically significantly related to air temperature in all stations, but as expected the downward IR was statistically significant in both in the multivariate regression and the multilevel model for all stations. Last, to determine whether the flux of moisture into the Arctic is dominantly local or from lower latitudes, I analyze the moisture flux convergence (MFC) using the ERA-I for the period 1979 to 2014. The direction of the flux vectors mainly originates from the midlatitudes, creating a positive trend of MFC over the Greenland Ice Sheet (GrIS), while moisture from the Arctic creates a negative trend of MFC over the GrIS. The results presented in this dissertation show the importance of understanding the cause of increasing temperatures in Arctic Amplification, as greenhouse gases continue to rise.