Department of Estuarine and Ocean Sciences MS Thesis Defense
When: Tuesday,
December 19, 2017
2:00 PM
-
3:00 PM
Where: > See description for location
Description: The School for Marine Science and Technology
Department of Estuarine and Ocean Sciences
MS Thesis Defense
"Inter-Annual Variability of Shelf Water Volume on the Northeastern Canadian and
United States Continental Shelf 1973-2013"
By
Alan Austin
Advisor
Wendell Brown
Committee:
James Bisagni
Avijit Gangopadhyay
Andre Schmidt
Geoffrey Cowles
Tuesday, December 19, 2017
2:00 pm
SMAST East, Room 101
836 S. Rodney French Blvd, New Bedford
Abstract
Understanding the waters confined to the northeastern United States and Canadian continental shelf region is essential to understanding factors which influence hydrographic patterns and structure, biota in terms of various fisheries stocks and planktonic assemblages, and how the impact of increased Arctic warming may affect the northeastern U.S. and Canadian continental shelf regions. Shelf waters (SHW) located on the continental shelf between Newfoundland and Cape Hatteras, are characterized by lower salinity (< 34 PSU) and lower temperatures than slope waters bordering it farther offshore. Multiple factors impact the volume of SHW, including local and remote river runoff and precipitation, release and equator-ward transport of fresh water from the arctic and sub-polar gyre, ice melt from Greenland, along with cross-shelf removal and both vertical and horizontal mixing processes. In this work, we estimated the inter-annual variability of SHW volume between the Newfoundland shelf and Cape Hatteras from 1973 through 2013. Objectively-analyzed (OA) annual mean SHW thickness along with its mean error as a percent of the data variance were computed for each of eleven sub-regions spanning our study domain for the 41-year period. Annual mean SHW volume was computed for each sub-region by multiplying the grid points contained within each sub-region by their respective OA annual mean SHW thicknesses. Results show significant decreasing trends in SHW volume within 5 of the 11 sub-regions (The Grand Banks through the Eastern Scotian Shelf sub-regions) in agreement with previous work which has shown a decreasing trend of Labrador Current transport. OA annual SHW volume anomalies were cross-correlated with annual mean shelf slope front (SSF) position anomalies for corresponding sub-regions, displaying a highly significant relationship for the Georges Bank, the Mid-Atlantic Bight, and the DelMarVa Hatteras shelf with higher volumes corresponding to more offshore SSF positions. Annual mean near-surface salinities cross-correlated with OA annual SHW volume displayed significant positive correlations from the GSL northeast to the NFS and displayed primarily negative correlations from the Gulf of Maine to the DelMarVa Hatteras sub-region. The North Atlantic Oscillation annual indices displayed only two significant cross-correlations with the OA SHW volume (Tail of the Grand Banks and Georges Bank), and there was no significant correlation computed between the OA annual SHW volume and the NAO winter index.
For additional information, please contact Sue Silva at s1silva@umassd.edu.
Department of Estuarine and Ocean Sciences
MS Thesis Defense
"Inter-Annual Variability of Shelf Water Volume on the Northeastern Canadian and
United States Continental Shelf 1973-2013"
By
Alan Austin
Advisor
Wendell Brown
Committee:
James Bisagni
Avijit Gangopadhyay
Andre Schmidt
Geoffrey Cowles
Tuesday, December 19, 2017
2:00 pm
SMAST East, Room 101
836 S. Rodney French Blvd, New Bedford
Abstract
Understanding the waters confined to the northeastern United States and Canadian continental shelf region is essential to understanding factors which influence hydrographic patterns and structure, biota in terms of various fisheries stocks and planktonic assemblages, and how the impact of increased Arctic warming may affect the northeastern U.S. and Canadian continental shelf regions. Shelf waters (SHW) located on the continental shelf between Newfoundland and Cape Hatteras, are characterized by lower salinity (< 34 PSU) and lower temperatures than slope waters bordering it farther offshore. Multiple factors impact the volume of SHW, including local and remote river runoff and precipitation, release and equator-ward transport of fresh water from the arctic and sub-polar gyre, ice melt from Greenland, along with cross-shelf removal and both vertical and horizontal mixing processes. In this work, we estimated the inter-annual variability of SHW volume between the Newfoundland shelf and Cape Hatteras from 1973 through 2013. Objectively-analyzed (OA) annual mean SHW thickness along with its mean error as a percent of the data variance were computed for each of eleven sub-regions spanning our study domain for the 41-year period. Annual mean SHW volume was computed for each sub-region by multiplying the grid points contained within each sub-region by their respective OA annual mean SHW thicknesses. Results show significant decreasing trends in SHW volume within 5 of the 11 sub-regions (The Grand Banks through the Eastern Scotian Shelf sub-regions) in agreement with previous work which has shown a decreasing trend of Labrador Current transport. OA annual SHW volume anomalies were cross-correlated with annual mean shelf slope front (SSF) position anomalies for corresponding sub-regions, displaying a highly significant relationship for the Georges Bank, the Mid-Atlantic Bight, and the DelMarVa Hatteras shelf with higher volumes corresponding to more offshore SSF positions. Annual mean near-surface salinities cross-correlated with OA annual SHW volume displayed significant positive correlations from the GSL northeast to the NFS and displayed primarily negative correlations from the Gulf of Maine to the DelMarVa Hatteras sub-region. The North Atlantic Oscillation annual indices displayed only two significant cross-correlations with the OA SHW volume (Tail of the Grand Banks and Georges Bank), and there was no significant correlation computed between the OA annual SHW volume and the NAO winter index.
For additional information, please contact Sue Silva at s1silva@umassd.edu.
Contact: > See Description for contact information
Topical Areas: School for Marine Sciences and Technology, SMAST Seminar Series