Assessing the impact of glacier retreat on organic matter export and cycling in Chilean Patagonia

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Organic matter is an important component of global biogeochemical cycles, which are sensitive to processes of landscape change. The worldwide retreat of mountain glaciers is one of the most profound examples of such change. Chilean Patagonia represents a unique study region, which is both relatively untouched by direct human activity and undergoing significant rates of deglaciation. The biogeochemical role of glaciers in this region is relatively understudied and this thesis offers the first regional scale assessment of the sensitivity of organic matter in rivers and fjords to glacier retreat. This assessment comprises three complementary studies. The first adopts a space-for-time approach, in which the effects of spatial variations in landscape properties on organic matter flux and composition are used to infer the effects of ongoing glacier retreat over time. It was found that glaciers drive higher catchment yields for particulate organic matter and supply dissolved organic matter rich in protein-like and aliphatic substances. However, the influence of glaciers is dampened by non-glacial sources and sinks in the downstream landscape. The second study used incubation experiments to quantify the proportion of bioavailable dissolved organic carbon in river water from selected catchments. These incubations showed that bioavailability in these catchments is lower than that observed in glacial rivers of the northern hemisphere. This may be explained by prior processing and specific intrinsic compositional factors but is not systematically related to catchment glacier cover. The third study presents the first molecular level analysis of dissolved organic matter in a glaciated fjord. This analysis showed that riverine organic matter may comprise a significant proportion of the total organic carbon pool, which is sensitive to changes in glacier melt inputs. The relationships between organic matter cycling and landscape change in Chilean Patagonia established in this thesis highlight some potential implications of deglaciation for global biogeochemistry.
Date of Award12 May 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SponsorsNatural Environment Research Council, Great Western Four Plus Doctoral Training Partnership
SupervisorJemma L Wadham (Supervisor)

Keywords

  • Chilean Patagonia
  • organic matter
  • glacier retreat
  • landscape change
  • FT-ICR MS
  • spectrofluorescence

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