Terrestrial and coloured dissolved organic matter in Arctic waters: Towards in-situ sensor based monitoring of Arctic-Atlantic organic carbon exchange at major Arctic gateways

• Main Author: Jensen, Anders Dalhoff Bruhn
• Format: Book
• Language: English
• Published: DTU Aqua 2023
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/climate_action; SDG 13 - Climate Action; /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; SDG 14 - Life Below Water; Arctic; Arctic Ocean; Gateway The; Fram Strait; Global warming; Ice; permafrost; Sea ice
• Online Access: https://orbit.dtu.dk/en/publications/ab2ccc25-c9f7-4c5e-b284-55378ca4debd; https://backend.orbit.dtu.dk/ws/files/328864919/PhD_thesis_Anders_Dalhoff_Bruhn.pdf; https://backend.orbit.dtu.dk/ws/files/328864921/Correction_sheet_Anders_Dalhoff_Bruhn.pdf

With accelerating global warming, air temperatures around the globe are increasing and the highest increase has been observed over the past decades, particularly in the Arctic region. An increase in air temperatures for the Arctic region will not only affect the rate of sea ice melting, but will also increase river discharge and erosion of riverbanks and coastlines. The latter processes will lead to more terrestrial dissolved organic matter (tDOM) being transported from land to the Arctic Ocean in the future. The fate of dissolved organic carbon (DOC) supplied as tDOM is of great concern, since it potentially can be transformed to carbon dioxide (CO 2 ) and be exchanged with the atmosphere. The aim of this Ph.D. thesis was to study the fate of tDOM in the Arctic Ocean and to develop an analytical method to quantify and trace its distribution from different sources. To understand the continuum of tDOM, the fate of the dissolved material was first investigated in the Arctic coastal zone (ACZ), where it is released, and later in Arctic major gateway, the Fram Strait, where it is exported to the Atlantic Ocean. My studies found that the fate of tDOM from coastal erosion depends on the permafrost soil type being dissolved into the coastal waters. The derived tDOM from three different permafrost types led to the development of three distinct marine bacterial communities, which also led to three different bacterial growth efficiencies. The difference in bacterial growth efficiency ultimately means that the carbon processing of the derived DOC, and the remineralization to CO 2 , from coastal erosion is greatly dependent on which permafrost soil type will erode into coastal waters. However, it was found that most of the DOC was likely refractory to rapid mineralization and may survive passage through the coastal zone. The refractory part of tDOM that survives the coastal zone will be exported to the open ocean, where it will follow ocean currents across the Arctic Ocean and under the sea ice. The water masses circulating ...