UoB BMVPs Ellen and Jonathan Martin Public Lecture: Neglected fluxes: Understanding the evolution of weathering as the Greenland Ice Sheet retreats

22 March 2018, 5.15 PM - 22 March 2018, 7.00 PM

Ellen Martin, Jonathan Martin

G25 Reynolds Lecture Theatre, Wills Memorial Building

UoB Benjamin Meaker Visiting Professors Ellen Martin and Jonathan Martin will present their public talk, Neglected fluxes: Understanding the evolution of weathering as the Greenland Ice Sheet retreats.
 
Studies of proglacial rivers draining the Greenland Ice Sheet (GrIS) document the discharge of large volumes of meltwater that impact sea level as well as fluxes of bioavailable nutrients derived predominantly from subglacial processes.  In contrast, little is known of fluxes from “deglaciated” watersheds that were exposed by ice sheet retreat and contain glacial sediment of variable exposure ages.  Non-glacial streams in deglaciated watersheds are disconnected from the GrIS and drain only local precipitation and active layer melt. Due to distinct water:rock ratios, sediment exposure ages, and climate conditions, variations in weathering contributions from proglacial and non-glacial streams as ice sheets retreat may drive alter ocean productivity, exchange with atmospheric CO2, and increases in deep sea Pb isotopes recorded over the last deglaciation. To evaluate differences in fluxes from pro- and non-glaciated streams, we sampled water, stream bedload, and bedrock from two proglacial and nine deglaciated watersheds in western and southern Greenland during field deployments in 2013 and 2017.  We also gauged several deglaciated streams in 2017.  We will present data that suggest (1) changes in radiogenic isotope ratios reflect differences in weathering extent in proglacial, inland deglaciated and coastal deglaciated watersheds, (2) weathering extent produces unique signatures of chemical weathering in each watershed, (3) specific discharge is similar between proglacial and coastal non-glacial streams, but smaller from inland non-glacial streams, and (4) hyporheic exchange is an important process for in-stream weathering of proglacial streams.  These results have implications for understanding past ice sheet dynamics and future impacts of ice sheet retreat on isotopic, nutrient and CO2 fluxes.
 
The lecture is open to all and will be followed by a drinks reception.
 
On the following day, both Ellen and Jonathan will be participating in a workshop
 

Contact information

ias-admin@bristol.ac.uk