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Weathering of western Greenland: Influences on oceanic fluxes of radiogenic isotopes

General

Organisation
Project start
01.01.2013
Project end
31.12.2015
Type of project
ARMAP/NSF
Project theme
Ocean & fiord systems
Project topic
Geology
Oceanography

Fieldwork / Study

Fieldwork country
Greenland (DK)
Fieldwork region
Greenland, Mid-West
Fieldwork location

Geolocation is 67.024061111111, -51.404241666667

Fieldwork start
12.07.2013
Fieldwork end
22.07.2013

SAR information

Fieldwork / Study

Fieldwork country
Greenland (DK)
Fieldwork region
Greenland, Mid-West
Fieldwork location

Geolocation is 67.0179977417, -50.69400024414

Fieldwork start
09.07.2013
Fieldwork end
02.08.2013

SAR information

Fieldwork / Study

Fieldwork country
Greenland (DK)
Fieldwork region
Greenland, Mid-West
Fieldwork location

Geolocation is 67.004930555556, -52.94057222222

Fieldwork start
24.06.2013
Fieldwork end
04.07.2013

SAR information

Fieldwork / Study

Fieldwork country
Greenland (DK)
Fieldwork region
Greenland, Mid-West
Fieldwork location

Geolocation is 66.93, -53.68

Fieldwork start
13.06.2013
Fieldwork end
08.07.2013

SAR information

Project details

02.10.2019
Science / project plan

.

Science / project summary
This project addresses the hypothesis that as the Greenland Ice Sheet (GrIS) retreats, increased exposure and weathering will alter fluxes of radiogenic isotopes to the oceans. Radiogenic strontium (Sr) and lead (Pb) isotopes, and non­radiogenic neodymium (Nd) are preferentially leached during initial weathering of fresh bedrock and sediments in glacial terrains. With increased duration and intensity of weathering, isotopic compositions of runoff approach parent rock values. Therefore, magnitudes of offsets for Sr, Nd and Pb isotope values between water and bedrock provide information about the extent of chemical weathering. Specific hypotheses to be tested are (1) more radiogenic Sr and Pb and less radiogenic Nd discharge in water originating from the GrIS than from deglaciated watersheds without connections to the ice sheet, (2) values of isotope ratios depend on the exposure age of the deglaciated watersheds and the intensity of weathering in each environment, and (3) the total flux of radiogenic isotopes from continental glaciers depends on the relative aerial extents of glaciated and deglaciated watersheds. These hypotheses will be tested in western Greenland near Kangerlussuaq, where retreat of the GrIS since the Last Glacial Maximum has exposed an approximately 175 km wide strip of land. Water, sediment, and moraine material will be sampled from subglacial streams discharging from the outlet portals of the Russell and Leverett Glaciers, in the proglacial watershed of the Watson River, and in four deglaciated watersheds, not connected to the GrIS that drain moraines ranging in age from about 600 to 18,000 years. Additional samples will be located from a deglaciated region near Sisimiut that has a wetter climate and older moraines. Water samples will be measured for major and trace element concentrations to model potential mineral dissolution and contributions to isotope fluxes, and for Sr, Nd, and Pb isotope ratios to assess their fluxes from subglacial, proglacial, and deglaciated watersheds. This work will link terrestrial weathering products in a continental glacier setting to oceanic fluxes of radiogenic isotopes, thereby improving our ability to interpret marine records. The work is important because of its location near the formation regions of North Atlantic Deep Water and it should contribute to planning for a proposed ocean drilling expedition off Greenland. The work will impact human resources through incorporation of 4 students from undergraduate to Ph.D. level, all of whom will participate in field work and will work collaboratively to complete laboratory and data analyses. Results of the work will be used in several graduate and undergraduate courses and will be presented at national and international scientific meetings and through publications. Outreach will include lectures at local schools, as invited speakers at colleges and universities, and in the annual open house at the Florida Museum of Natural History.
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