An analysis of Atlantic Water in the Arctic Ocean using the Arctic Subpolar Gyre State Estimate and observations

• Main Author: Grabon, Jeffrey S.
• Other Authors: Toole, John M.
• Format: Thesis
• Language: English
• Published: Massachusetts Institute of Technology and Woods Hole Oceanographic Institution 2020
• Subjects: Atlantic water; Arctic Ocean; Arctic Subpolar Gyre State Estimate; Arctic; Fram Strait; Lomonosov Ridge; Sea ice
• Online Access: https://hdl.handle.net/1912/26071

Submitted in partial fulfillment of the requirements for the degree of Master of Science in Physical Oceanography at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2020. The Atlantic Water (AW) Layer in the Arctic Subpolar gyre sTate Estimate (ASTE), a regional, medium-resolution coupled ocean-sea ice state estimate, is analyzed for the first time using bounding isopycnals. A surge of AW, marked by rapid increases in mean AW Layer potential temperature and AW Layer thickness, begins two years into the state estimate (2004) and traverses the Arctic Ocean along boundary current pathways at approximately 2 cm/s. The surge also alters AW flow direction and speed including a significant reversal in flow direction along the Lomonosov Ridge. The surge results in a new quasi-steady AW flow from 2010 through the end of the state estimate period in 2017. The time-mean AW circulation during this time period indicates a significant amount of AW spreads over the Lomonosov Ridge rather than directly returning along the ridge to Fram Strait. A three-layer depiction of ASTE’s overturning circulation within the AO indicates AW is converted to colder, fresher Surface Layer water at a faster rate than is transformed to Bottom Water (1.2 Sv vs. 0.4 Sv). Observed AW properties compared to ASTE output indicate increasing misfit during the simulated period with ASTE’s AW Layer generally being warmer and thicker than in observations. This research was funded via the United States Navy’s Civilian Institution Program with the MIT/WHOI Joint Program (JP). The thesis supervisor’s participation in this project was supported by National Science Foundation-Grant #PLR-1603660 and by Office of Naval Research-Grant #N000141612381. This project, specifically ASTE developed by Dr. An T. Nguyen, is also supported by National Science Foundation-Grant #PLR-1603903.