Cruise JR175 West Greenland and Baffin Bay “Marine geophysical and geological investigations of past flow and stability of a major Greenland ice stream.

Cruise JR175

West Greenland and Baffin Bay

“Marine geophysical and geological investigations of past flow and stability of a major Greenland ice stream

in the late Quaternary”

Cruise Location “TMF” = Trough Mouth Fan

West Central Greenland Ice Sheet – an area of rapid glacier thinning and break-up

Recent retreat of Jakobshavns Isbrae

Rationale

(A) Subglacial landforms recording former ice flow, Antarctic Peninsula shelf

Drumlins & lineations

(B) Sediment core from subglacial landforms in (A)

To reconstruct the behaviour of fastest ice stream to drain the modern Greenland Ice Sheet, Jakobshavns Isbrae (JI) during the Late Quaternary (last ~45,000 years).

Overall scientific goal & questions to be addressed by cruise

1. How extensive was JI during the Late Quaternary, and especially at the LGM? What controlled its flow, and when and how rapidly did it last retreat from the continental shelf?

2. What is the longevity of JI? Is it a relatively recent phenomenon or did it exist continuously throughout the last 45,000 years?

3. Has JI undergone abrupt collapse during the Late Quaternary or has it been relatively stable?

4. How has JI responded to more recent (last 5000 years) Holocene climatic variations?

Target for Data Collection – Cross Shelf Bathymetric Trough

1. How extensive was JI during the Late Quaternary, & especially the LGM? What controlled its flow, & when

& how rapidly did it last retreat from the shelf?

• Vibro-, gravity and box coring to obtain sediment records from the trough.

• Map glacial landforms and acoustic stratigraphy across the shelf using EM120 multibeam & TOPAS sub-bottom profiling.

Target for Data Collection – Continental Slope Sediment Fan

2. What is the longevity of JI? A relatively recent phenomenon or has it existed continuously throughout the last 45 kyr?

• Vibro-coring to obtain sediment records from fan that will allow identification of repeated advances of JI to the shelf edge.

• EM120 multibeam and TOPAS sub-bottom profiling of sediment fan at trough mouth.

Target for Data Collection – Deep Sea Basin

3. Has JI undergone abrupt collapse during the Late Quaternary or has it been relatively stable?

• Vibro- and gravity coring to obtain deep-sea sediment records of past JI activity.

• Core sites selected from TOPAS data

Target for Data Collection – Inner Shelf Basins

• Vibro-, gravity and box coring to obtain sediments from deep basins in the inner part of Disko Bugt.

4. How has JI responded to more recent (last 5000 years) Holocene climatic variations?

• Core sites selected from TOPAS