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64°5'10"N0 42 km
Key
^ Norse ruinMoraine
Trimline
Flute
Meltwater Channel
Water
¯The project investigates Kangiata Nunaata Sermia (KNS), the
mostdynamic tidewater glacier in southwest Greenland, having
retreated >22
km since its Little Ice Age maximum (LIAmax) in 1761 (Lea et al.
2014a;b;
Figure 1).
The site's has a unique combination of terrestrial (glacial
geomorphology,
sedimentology, and Norse archaeology) and novel marine
evidence
(coralline algae - Lithothamnion glaciale), which enable both
its advance and
retreat over the last millennium to be reconstructed. Here, we
present field
data for KNS collected during summer 2015.
Danni Pearce1*, Doug Mair2, Brice Rea1, Ed Schofield1, James
Lea2;3, Nick Kamenos4,
Kate Schoenrock4 and Lukasz Stachnik4
1 University of Aberdeen, School of Geosciences, Elphinstone
Road, Aberdeen , AB24 3UF, Scotland, U.K.; 2 School of
Environmental Sciences, University of Liverpool, Liverpool, L69
3GP, U.K. 3 Stockholm University, Department of Physical Geography
and Quaternary Geology, 106 91, Stockholm, Sweden; 4 University of
Glasgow, Gregory Building, Lilybank Gardens, Glasgow, G12 8QQ,
U.K.
*Email: [email protected]
Reconstructing the behaviour of a major SW Greenland tidewater
glacier
over the last millennium
Greenlandic tidewater glaciers have experienced widespread
retreat over the
last century (Moon and Joughin, 2008; Moon et al., 2012). Prior
to this,
information on their dynamics is poorly constrained due to a
lack of
observations and reworking during the Little Ice Age (LIA; c.
1250 – 1900
AD; Long et al., 2012). This restricts our understanding of the
long-term
(centennial-millennial timescale) relationships between climate
and calving
at marine terminating margins in Greenland.
1. Introduction
Figure 1. Location of KNS and Kangersuneq Fjord, southwest
Greenland. Showing the
location of two Norse settlements and the ice-marginal lake,
Isvand. The black boxes
represent the aerial extent on Figures 2 and 3. Inset, bottom
right, is the location of KNS
in Greenland and inset, middle left, is a satellite image of the
fjords surrounding KNS.
2. Terrestrial dataGlacial landforms were digitally mapped using
a combination of colour
aerial photos in arc2earth, and a digital elevation model (DEM).
Where
possible, the mapping was ground-truthed, during fieldwork
conducted in
August 2015, and complied in a GIS data base.
The free living coralline algae Lithothamnion glaciale is known
to dominate subtidal
habitats in the marine and fjord systems of south western
Greenland (Figure 9).
This is unique species of algae that whose calcified thallus
lays down annual
bands that can be used in schlerochronology (Figure 9B).
4. Future researchFuture work will involve:
• The 14C dates collected in 2015 will help constrain the
advance of KNS
down the Kangersuneq fjord. Palynological analysis from peat
cores,
collected in 2015, will be used to determine the settlement
and
abandonment dates of Norse settlements proximal to the
glacier.
• The terrestrial 2016 field campaign will focus on obtaining
further 14C and
OSL samples from lakes which were also ice-dammed during the
LIA.
• Isotopic analysis of annually banded coralline algae to
interrogate changes
in fjord water conditions.
These will contribute towards a millennial timescale record of
glacier dynamics
that will help to validate models linking calving to climate, in
addition to
potentially casting light on the latter stages of the Norse
Western Settlement
(Vestyrbygd) in Greenland.
3. Marine data
The ratios of Mg- Ca within the skeletal lattice of the alga aid
in recreating
temperature of their environment and 18O is used to calculate
salinity for the
past 10-100s of years (Kamenos et al., 2012). These data will
corroborate
terrestrial proxies for calving events of the tidewater glacier.
Samples were
collected by hand on SCUBA from 10m depth and kept at 4°C. The
samples
will be processed at the University of Glasgow.
Terrestrial data
Figure 2. Geomorphological map of KNS and Kangaasarsuup Sermia,
south-west
Greenland. The LIA is clearly defined by the vegetation
trim-line, the presence of
glacially scoured bedrock and/or moraines located beyond the
present ice surface.
Beyond the LIAmax prominent moraine systems are present at lower
altitudes as well as
extending beyond the confines of the valley (e.g.
Austmannadalen). Their age has been
attributed to the 8.2 ka cold event (Weidick et al., 2012) and
c. 10.4 ka BP (Larsen et al.,
2014) but remains uncertain. The black circle represents the
photo locations below.
Isvand
1040 m
868 m
1022 m
847 m
Figure 3. Geomorphological map of Qamanaarsuup Sermia (QS),
south-west
Greenland. The LIAmax was reconstructed from the
geomorphological evidence
presented in Lea et al., (2014). As KNS advanced down-valley, to
its maximum position,
it dammed meltwater from QS, which provides the opportunity to
date the timing of the
advance of KNS. 14C samples are being processed to constrain the
timing of the
advance (Figure 5).
Figure 9 A) Two Lithothamnion glaciale
maerli thalli; B) Annual growth bands
present in a traverse.
References: Kamenos et al. (2012). Geology, 40 (12); Larsen et
al., (2014). Quaternary Science Reviews, 92; Lea et
al. (2014a). The Cryosphere, 8; Lea et al. (2014b). Journal of
Glaciology, 60, 220; Lukas (2006).
Progress in Physical Geography, 30 (6); Long et al. (2012).
EPSL, 315-316; Moon and Joughin
(2008). JGR, 113(F2); Moon et al. (2012). Science. 336(6081);
Weidick et al., (2012). Geological
Survey of Denmark Greenland, 27.
Figure 6. Section through a probable anthrosol at ruin group
V53d in Austmannadalen
(see Figure 2). The dark band at the base of the organic deposit
may reflect a burnt
(clearance) horizon that is contemporary with the establishment
of the farm.
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0 84 km
Key
^ Norse ruinWater
Glacier
Glacier Contours
¯Figure 3.
Figure 2.
Umiivik
Umivik
1040 m
868 m
Location of Figure 5
V53d
Location of Figure 6
Figure 5. Palaeo-lake sediments located in the proglacial area
of QS (see Figure 3). The
darker brown areas are an organic layer (peat), which is
discontinuous throughout the
lake sediments. Both the peat and lake sediments were sampled
for 14C dating. This
multi-proxy approach will enable a robust approach to establish
the timing of the
advance of KNS to its LIAmax.
Figure 8. Ruins of a Norse farmstead at
Umívik (V15), Western Settlement,
Greenland (see Figure 3). A dwelling
comprising multiple rooms is visible in the
foreground.
Figure 4. Isvand lake (see Figure 2 for location). Retreat,
following the LIAmax, created
the IDL Isvand. For at least c. 250 years it drained westward
down Austmannadalen. In
2004 Isvand’s drainage changed to the north, towards the calving
front, as KNS receded.
These changes combined with evidence from Norse settlement
patterns in
Austmannadalen will help us to determine the advance of KNS out
to the LIAmaxposition.
Figure 7. Pre-LIA moraine in Umiviik
valley. Interpreted as being associated with
the Kapisgdlit Stade, which is either
associated with the 8.2 Event (Weidick et al.,
2012) or early Holocene (c.10.1 ± 0.4 ka;
Larsen et al., 2014). Further chronological
control would be required to confidently
assign the moraines to either time-slice.
Figure 10. Contemporary reconstruction of temperature from
core-top
coralline algae (Mg/Ca). A) Fjord temperature (directly
influenced by
runoff). B) marine temperature, which is warmer than fjord
temperature
as glacial water runoff is not reducing the temperatures, C)
instrumental
temperature from 10m depth at Nuuk, Greenland
UB-31333
UB-31334
Montia fontana seeds
combined for 14C
Charcoal fragments
Bark sampled for 14C dating
(unknown species).
OSL sampling in a gully through an
incised fan, which drains into Isvand.
Gully is c. 5 m wide and 30 m in
height.
