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SUMMARY:Disentangling polar biogeochemistry through (silicon) isotope geoc
 hemistry - Kate Hendry\, British Antarctic Survey
DTSTART:20220120T150000Z
DTEND:20220120T160000Z
UID:TALK163231@talks.cam.ac.uk
CONTACT:Oscar Branson
DESCRIPTION: The polar regions are home to important and dynamic component
 s of the silicon cycle\, from subglacial weathering to biological producti
 on and carbon sequestration in marine sediments by silicifiers. The Arctic
 \, parts of the Antarctic\, and glaciated mountain ranges (the ‘third po
 le’) are also some of the most climatically sensitive locations on Earth
 \, where the most dramatic warming and associated physical and chemical ch
 anges have been observed in recent decades. If we are to comprehend the im
 plications of anthropogenic climate change for future oceans\, we need to 
 examine how such rapid change in the polar regions could be either amplifi
 ed or mitigated by silicon cycle feedback mechanisms. Here\, we will explo
 re polar silicon cycling through the lens of isotope studies. \n\nSubglaci
 al weathering in polythermal (“wet-based”) glacial systems—mobilises
  silicon\, both in dissolved form (DSi) and as reactive\, amorphous partic
 ulates. However\, the degree to which (and rate at which) this bioavailabl
 e silicon reaches the ocean or remains trapped within coastal fjord system
 s by physical\, chemical and biological processes remains a matter of deba
 te. Another major unknown is the role of fjord and marine sediments in sil
 icon cycling: are particulate reactive silica phases (glacial weathering p
 roducts\, biogenic opal) preserved within sediments\, or does sedimentary 
 cycling release DSi back into the overlying water? We can use stable silic
 on isotopes to begin the careful disentangling of these different processe
 s\, each of which results in different—but overlapping—fractionation. 
 We use Arctic and Chilean Patagonian case studies to illustrate how these 
 silicon isotope measurements can be coupled together with trace metals and
  their stable isotopes\, and radioisotopes\, to build a more complete pict
 ure of the nature and rates of important silicon cycling components that a
 re active in glaciated environments
LOCATION:Department of Earth Sciences\, Tilley Lecture Theatre
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