東華大學圖書館 |

Evaluating Fjord and Coastal Sea Surface Temperatures and Their Implications for Glacier Variability in Greenland and Antarctica.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Evaluating Fjord and Coastal Sea Surface Temperatures and Their Implications for Glacier Variability in Greenland and Antarctica./
作者:	Snow, T. M.
面頁冊數:	1 online resource (147 pages)
附註:	Source: Dissertations Abstracts International, Volume: 82-11, Section: B.
Contained By:	Dissertations Abstracts International82-11B.
標題:	Remote sensing. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28316920click for full text (PQDT)
ISBN:	9798738626845

Evaluating Fjord and Coastal Sea Surface Temperatures and Their Implications for Glacier Variability in Greenland and Antarctica.
Snow, T. M.

Evaluating Fjord and Coastal Sea Surface Temperatures and Their Implications for Glacier Variability in Greenland and Antarctica. - 1 online resource (147 pages)

Source: Dissertations Abstracts International, Volume: 82-11, Section: B.

Thesis (Ph.D.)--University of Colorado at Boulder, 2021.

Includes bibliographical references

The Greenland Ice Sheet contributes one-quarter of global sea level rise each year, and approximately half of its loss occurs at outlet glaciers along its periphery. Antarctica's contributions are more uncertain, but ice loss has been increasing, especially in the Amundsen Sea sector of the West Antarctic Ice Sheet. Glacier melting caused by interactions with relatively warm ocean water is a primary mechanism for these ice losses, and it can lead to large ice instabilities, ice loss, and rapid sea level rise. Field measurements are the predominant method for studying these harsh and remote ocean environments but in many areas of the Greenland and Antarctic coast, records extend back only a decade or less and in few locations. Since many glaciers began to change before those records began, the lack of measurements requires us to rely on an understanding of contemporary ocean processes and, from that, make inferences of past conditions to evaluate the ocean's role in observed glacier change. Here, I show that satellite-derived sea surface temperatures (SST) can provide insight into glacier-ocean interactions, and accurate records of SSTs extend back more than two decades. I explore the utility of SST in expanding ocean observations near Greenland and Antarctica using measurements from the two MODerate resolution Imaging Spectroradiometers (MODIS) on the Aqua and Terra satellites, and the Landsat 8 Thermal Infrared Sensor (TIRS). Using these datasets, I build methods to estimate surface and subsurface water temperatures in southeastern Greenland, investigate the mechanisms driving warm water onto the continental shelf toward the Greenland coastline, and characterize the coastal current in the Amundsen Sea in Antarctica, all of which have implications for the amount of heat delivered to the glaciers in the respective systems. In my first chapter, I investigate the use of sea surface temperatures acquired by satellites to assess ocean temperature changes through time. I explore their use near the southeastern Greenland coast, where warm water circulates from the North Atlantic Ocean onto the continental shelf and eventually reaches Helheim Glacier, one of Greenland's largest glaciers. Through a comparison with ocean instruments, I find that sea surface temperatures serve as a good indicator of upper ocean temperatures in this region once proper corrections are applied. With these records, I find that the dilution of warm waters, with cold Polar Water, as they circulate from the North Atlantic changes over time and governs the temperature of the water that eventually reaches Helheim, which was previously unknown. My work shows that sea surface temperatures can provide new insight into the ocean changes that may have impacted glacier retreat before ocean instruments were deployed.Higher transport of warm Atlantic Waters into Greenland fjords has driven glacier ice loss, but the mechanisms transporting those waters to the glacier remain poorly characterized. In my second chapter, I use visible imagery and SST methods constructed in the first chapter to identify a wind-driver for warm Atlantic Water inflow toward Sermilik Fjord abutting Helheim Glacier. Often associated with the passing of cyclones, wind events cause upwelling and inflow of Atlantic Water from offshore onto the continental shelf along a submarine trough that leads to Sermilik Fjord. This inflow of warm waters occurs as a result of unique circulation that is stimulated by a bathymetric trough. My measurements show that when these intrusion events draw Atlantic Water all the way to the coast they produce warming, measured using ocean instruments, near Sermilik Fjord mouth and within the fjord. This mechanism for driving heat inshore along a bathymetric trough has been previously unrecognized around Greenland, but may occur in other Greenland glacier systems and, therefore, play an important role in broader ice sheet mass loss.In the third chapter of my dissertation, I use sea surface temperatures alongside field observations to characterize the Antarctic Coastal Current (AACC) in the eastern Amundsen Sea, West Antarctica, where many large glaciers and ice shelves are rapidly losing ice. The location and properties of the current in eastern Amundsen Sea are unknown, though the current likely plays an important role in heat transport to the ice fronts. Using field measurements taken by ship-based instruments, autonomous underwater gliders, and seal tags in 2019, I find that the AACC is comprised of relatively fresh waters, predominantly flows along the ice shelves, and is likely located in the top 100 m of the water column, similar to the current in other regions of Antarctica. I construct a new sea surface temperature processing algorithm that builds on the methods from my first two chapters and use the sea surface temperatures to better constrain the spatial and temporal variability in the AACC at the surface. I suggest that shifts in the coastline structure or AACC location as ice shelves retreat may change the distance at which the AACC flows from the ice front, thereby changing the amount of heat delivered to the ice and having potential impacts on glacier stability.In the three chapters of this dissertation, I show that sea surface temperatures provide novel, critical, and fundamental observations of ocean circulation around Greenland and Antarctica that compliment more conventional field-based oceanographic methods. With the longer-term and more spatially comprehensive oceanographic observations that sea surface temperatures provide, my dissertation provides new insight into ocean and ice variability that will be applicable to wider ice sheet questions.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798738626845Subjects--Topical Terms:

535394
Remote sensing.
Subjects--Index Terms:

GlacierIndex Terms--Genre/Form:

542853
Electronic books.

Evaluating Fjord and Coastal Sea Surface Temperatures and Their Implications for Glacier Variability in Greenland and Antarctica.
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Since many glaciers began to change before those records began, the lack of measurements requires us to rely on an understanding of contemporary ocean processes and, from that, make inferences of past conditions to evaluate the ocean's role in observed glacier change. Here, I show that satellite-derived sea surface temperatures (SST) can provide insight into glacier-ocean interactions, and accurate records of SSTs extend back more than two decades. I explore the utility of SST in expanding ocean observations near Greenland and Antarctica using measurements from the two MODerate resolution Imaging Spectroradiometers (MODIS) on the Aqua and Terra satellites, and the Landsat 8 Thermal Infrared Sensor (TIRS). Using these datasets, I build methods to estimate surface and subsurface water temperatures in southeastern Greenland, investigate the mechanisms driving warm water onto the continental shelf toward the Greenland coastline, and characterize the coastal current in the Amundsen Sea in Antarctica, all of which have implications for the amount of heat delivered to the glaciers in the respective systems. In my first chapter, I investigate the use of sea surface temperatures acquired by satellites to assess ocean temperature changes through time. I explore their use near the southeastern Greenland coast, where warm water circulates from the North Atlantic Ocean onto the continental shelf and eventually reaches Helheim Glacier, one of Greenland's largest glaciers. Through a comparison with ocean instruments, I find that sea surface temperatures serve as a good indicator of upper ocean temperatures in this region once proper corrections are applied. With these records, I find that the dilution of warm waters, with cold Polar Water, as they circulate from the North Atlantic changes over time and governs the temperature of the water that eventually reaches Helheim, which was previously unknown. My work shows that sea surface temperatures can provide new insight into the ocean changes that may have impacted glacier retreat before ocean instruments were deployed.Higher transport of warm Atlantic Waters into Greenland fjords has driven glacier ice loss, but the mechanisms transporting those waters to the glacier remain poorly characterized. In my second chapter, I use visible imagery and SST methods constructed in the first chapter to identify a wind-driver for warm Atlantic Water inflow toward Sermilik Fjord abutting Helheim Glacier. Often associated with the passing of cyclones, wind events cause upwelling and inflow of Atlantic Water from offshore onto the continental shelf along a submarine trough that leads to Sermilik Fjord. This inflow of warm waters occurs as a result of unique circulation that is stimulated by a bathymetric trough. My measurements show that when these intrusion events draw Atlantic Water all the way to the coast they produce warming, measured using ocean instruments, near Sermilik Fjord mouth and within the fjord. This mechanism for driving heat inshore along a bathymetric trough has been previously unrecognized around Greenland, but may occur in other Greenland glacier systems and, therefore, play an important role in broader ice sheet mass loss.In the third chapter of my dissertation, I use sea surface temperatures alongside field observations to characterize the Antarctic Coastal Current (AACC) in the eastern Amundsen Sea, West Antarctica, where many large glaciers and ice shelves are rapidly losing ice. The location and properties of the current in eastern Amundsen Sea are unknown, though the current likely plays an important role in heat transport to the ice fronts. Using field measurements taken by ship-based instruments, autonomous underwater gliders, and seal tags in 2019, I find that the AACC is comprised of relatively fresh waters, predominantly flows along the ice shelves, and is likely located in the top 100 m of the water column, similar to the current in other regions of Antarctica. I construct a new sea surface temperature processing algorithm that builds on the methods from my first two chapters and use the sea surface temperatures to better constrain the spatial and temporal variability in the AACC at the surface. I suggest that shifts in the coastline structure or AACC location as ice shelves retreat may change the distance at which the AACC flows from the ice front, thereby changing the amount of heat delivered to the ice and having potential impacts on glacier stability.In the three chapters of this dissertation, I show that sea surface temperatures provide novel, critical, and fundamental observations of ocean circulation around Greenland and Antarctica that compliment more conventional field-based oceanographic methods. With the longer-term and more spatially comprehensive oceanographic observations that sea surface temperatures provide, my dissertation provides new insight into ocean and ice variability that will be applicable to wider ice sheet questions.
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