Jon Hawkings - SMSP Spring Seminar Series 2023

 Glaciers have covered ~10-30 % of land surface over the past 100,000 years and are sensitive barometers of climatic change, yet are rarely considering in conceptual models of regional or global biogeochemical cycles. For example, textbooks illustrating river catchment fluxes of solute and sediment to the ocean regularly display ice sheets (continental glaciers) as blank spots. Research over the past two decades now indicates that far from being sterile, adynamic blocks of ice, glaciers are biomes harbouring truncated ecosystems on their surfaces (a “living skin”) and at their beds (the subglacial environment). Glaciers can also maintain very high physical denudation rates and chemical weathering rates at or even above most global riverine catchments, with consequences for cycling of rock-derived nutrients and the carbon cycle. During this seminar I will present research linking subglacial weathering, elemental mobilization and export of bioessential elements to downstream systems. The focus of my talk will be on the sources, concentrations, speciation and transport of the essential micronutrient iron from glaciers into fjord and near-coastal ecosystems, using examples from the Greenland Ice Sheet, an Antarctic subglacial lake and the rivers and fjords of Chilean Patagonia. I will argue that glaciers are far from the frozen wastelands they are often portrayed in textbooks and should be considered as dynamic components of global biogeochemical cycles both now and in the past.