26 The holoceNe hisTory of Nares sTraiT B y a N N e e . J e N N i N g s , c h r i s T i N a s h e l d o N , T h o m a s m . c r o N i N , P i e r r e f r a N c u s , J o s e P h s T o N e r , a N d J o h N a N d r e w s Transition from glacial Bay to arctic-atlantic Throughflow Oceanography | Vol.24, No.3 26 moderate resolution imaging spectroradiometer (modis) image from august 2002shows the summer thaw around ellesmere island, canada (west), and Northwest greenland (east). as summer progresses, the snow retreats from the coastlines, exposing the bare, rocky ground, and seasonal sea ice melts in fjords and inlets. Between the two landmasses, Nares strait joins the arctic ocean (north) to Baffin Bay (south). From http: //visibleearth.nasa.gov/view_rec.php?id=3975 T h e c h a N g i N g a r c T i c o c e a N | s P e c i a l i s s u e o N T h e i N T e r N aT i o N a l P o l a r y e a r ( 2 0 0 7 -2 0 0 9)

Citation for published item:heldonD gF nd tenningsD eF nd endrewsD tFF nd ¡ y gofighD gF nd rognD uF nd howdeswellD tFeF nd eidenkrntzD wFEF @PHITA 9se strem retret following the vqw nd onset of the west qreenlnd urrent in ummnnq roughD west qreenlndF9D uternry siene reviewsFD IRU F ppF PUERTF Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. The deglacial history and oceanography of Uummannaq Trough, central West Greenland 24 continental shelf, was investigated using foraminiferal, sedimentological, and bathymetric 25 records together with a radiocarbon chronology, providing a timeline for the retreat of glacial 26 ice after the Last Glacial Maximum (LGM). To map ice stream retreat, data were collected from 27 cores from the outer (JR175-VC45 and JR175-VC43) and inner (JR175-VC42) Uummannaq 28 Trough. A large ice stream, fed by confluent glaciers draining the interior of the Greenland Ice 29Sheet, extended across the outer shelf during the LGM and was retreating by 15.0 cal kyr BP. 30Foraminiferal data indicate that the 'warm' West Greenland Current (WGC) was established 31 prior to 14.0 cal kyr BP, which is the hitherto earliest record of Atlantic Water found on the 32 West Greenland shelf. For each of the cores, foraminifera indicate that ice sheet retreat was 33 followed quickly by incursion of the WGC, suggesting that the warm water may have 34 enhanced ice retreat. Prior to the Younger Dryas cold event, the existing radiocarbon 35 chronology indicates that the ice sheet retreated to the mid-shelf, where it subsequently 36 stabilised and formed a large grounding-zone wedge (GZW). After the Younger Dryas, around 37 11.5 cal kyr BP, the ice retreated rapidly from the GZW and into the fjords.

*Manuscript Click here to view linked References 2 2 Three radiocarbon dated sediment cores from trough mouth fans on the central west Greenland continental slope were studied to determine the timing and processes of Greenland Ice Sheet (GIS) retreat from the shelf edge during the last deglaciation and to test the role of ocean forcing (i.e. warm ocean water) thereon. Analyses of lithofacies, quantitative x-ray diffraction mineralogy, benthic foraminiferal assemblages, the sea-ice biomarker IP 25 , and  18 O of the planktonic foraminifera Neogloboquadrina pachyderma sinistral from sediments in the interval from 17.5-10.8 cal ka BP provide consistent evidence for ocean and ice sheet interactions during central west Greenland (CWG) deglaciation. The Disko and Uummannaq ice streams both retreated from the shelf edge after the last glacial maximum (LGM) under the influence of subsurface, warm Atlantic Water. The warm subsurface water was limited to depths below the ice stream grounding lines during the LGM, when the GIS terminated as a floating ice shelf in a sea-ice covered Baffin Bay. The deeper Uummannaq ice stream retreated first, (ca. 17.1 cal ka BP), while the shallower Disko ice stream retreated at ca. 16.2 cal ka BP. The grounding lines were protected from accelerating mass loss (calving) by a buttressing ice shelf and by landward shallowing bathymetry on the outer shelf. Calving retreat was delayed until ca. 15.3 cal ka BP in the Uummannaq Trough and until 15.1 cal ka BP in the Disko Trough, during another interval of ocean warming. Instabilities in the Laurentide, Innuitian and Greenland ice sheets with outlets draining into northern Baffin Bay periodically released cold, fresh water that enhanced sea ice formation and slowed GIS melt. During the Younger Dryas, the CWG records document strong cooling, lack of GIS meltwater, and an increase in iceberg rafted material from northern Baffin Bay. The ice sheet remained in the cross-shelf troughs until the early Holocene, when it retreated 3 3 rapidly by calving and strong melting under the influence of atmosphere and ocean warming and a steep reverse slope toward the deep fjords. We conclude that ocean warming played an important role in the palaeo-retreat dynamics of the GIS during the last deglaciation.

Along the West Greenland continental margin adjoining Baffin Bay, bathymetric data show a series of large submarine fans located at the mouths of cross‐shelf troughs. One of these fans, termed here ‘Uummannaq Fan’, is a trough‐mouth fan built largely by debris delivered from a fast‐flowing outlet of the Greenland Ice Sheet during past glacial maxima. Cores from this fan provide the first information on glacimarine sedimentary facies within a major West Greenland trough‐mouth fan and on the nature of Late Weichselian–Holocene glacigenic sediment delivery to this region of the Baffin Bay margin. Glacigenic debris flows deposited on the upper slope and extending to at least 1800 m water depth in front of the trough‐mouth are related to the remobilization of subglacial debris that was delivered onto the upper slope at times when an ice stream was positioned at the shelf edge. In contrast, sedimentary facies from the northern sector of the fan are characterized by hemipelagic and ice‐rafted sediments and turbidites; glacigenic debris flows are notably absent in cores from this region. Quantitative X‐ray diffraction studies of the <2‐mm sediment fraction indicate that the bulk of the sediment in the fan is derived from Uummannaq Trough but there are distinct intervals when sediment from northern Baffin Bay sources dominates, especially on the northern limit of the fan. These data demonstrate considerable variation in the nature of sediment delivery across the Uummannaq Fan when the Greenland Ice Sheet was at the shelf edge. They highlight the variability of glacimarine depositional processes operating on trough‐mouth fans on high‐latitude continental margins during the last glacial maximum and indicate that glacigenic debris flows are just one of a number of mechanisms by which such large depocentres form. Copyright © 2012 John Wiley & Sons, Ltd.

Benthic foraminiferal assemblages supported by selected geochemical data from three marine sediment cores collected in Placentia Bay, SE Newfoundland, are used to construct an ~13,000-year-long record of regional oceanographic changes in the SW Labrador Sea. The area is located in the boundary zone between the cold, ice-loaded Labrador Current (LC) in the north and the warm Gulf Stream (GS) waters to the south. After the Younger Dryas termination, the influence of GS-derived water increased and was further strengthened at 10.7 cal. kyr BP through enhanced northward flow of Atlantic water via the Slopewater Current. A short-term event of increased terrestrial input and water column stratification at 8.4 cal. kyr BP was likely linked to the distal drainage of glacial Lake Agassiz. After 7.3 cal. kyr BP, a stronger LC weakened the inflow of warmer subsurface waters from the GS. This may be explained by extensive meltwater release from ice sheets in Arctic Canada and is concurrent with a general shift in oceanographic conditions in the Labrador Sea region. Around 4.0 cal. kyr BP, conditions became more stable with a slight increase in salinity, indicating a decrease in meltwater transported via the LC. The Northern Hemisphere neoglacial cooling around 2.8 cal. kyr BP was characterized off SE Newfoundland by a further stabilization of the current system, dominated by the LC with some continued influx of GS water.