PLAN – LANGAJöKULL 1999
SPECIFIC OBJECTIVES
This project objective is to study the behaviour of the whole of a small, relatively
assessable ice cap resting on a deformable bed (Langajökull, Iceland), to investigate
the effects of subglacial dynamics on the response of an ice cap to climatic forcing.
This will include:
a) ice cap survey: - glacier velocity measurements (by large area SAR interferometry
and smaller area GPS survey), mass balance studies, ice radar studies and
geomorphological mapping:
b) ice cap modelling : incorporation of sediment deformation into an existing
thermomechanical ice sheet model; testing of the model using spatial patterns of
surface velocity and a comparison of the simulated Holocene evolution with that
derived from geomorphological mapping.
c) subglacial investigations: -by in situ subglacial process studies (via hot water
drilling, to record subglacial sediment movement and water pressures, recover
subglacial samples, visually observe the subglacial environment with a video
camera), and geotechnical testing of subglacial till by triaxial and deformation tank
experiments.
In order to achieve this we have the following projects based on the above and
numbered accordingly. They will take place in a number of possible locations at
Vestari Hagafellsjökull:
a)
b)
c)
d)
e)
f)
10m ice thickness site (10)
100m ice thickness site (100)
Possible transect back down the glacier (depending on results) (T)
Unspecified glacier surface (G)
Unspecified Proglacial area (P)
Drumlin site (D)
For each project I have named one individual to take responsibility for the project,
with others included as co-workers. Where I have written “all”, this means anyone
who is free or keen can be involved.
Project or activity
HOT WATER DRILLING
Sites
10, 100, T
1
2
VELOCITY DISTRIBUTION IN ICE
MASS BALANCE
10, 100, T, P
G, P
3
4
5
GEOMORPHOLOGICAL MAPPING
TEPHRA SAMPLING
THICKNESS OF SUBGLACIAL
SEDIMENT
VELOCITY DISTRIBUTION IN
SUBGLACIAL SEDIMENT
SUBGLACIAL HYDROLOGY
SUBGLACIAL SAMPLING
PROGLACIAL SAMPLING
VISUALISATION
P, D
G
10, 100, T
Personnel
MT + all (except
HC)
NE + all
TP +HC to collect
data once
instruments in
place
NE + AJ, HC
HC + all
NE + all
100
NE + all
100 + T?
10, 100 + T?
P, D
10,100, T,G,P
TP/DB + all
CS + all
CS + AJ +all
KM/AJ + all
6
7
8
9
10
HOT WATER DRILLING
To enable the following projects (borehole camera to be used during drilling to locate
depth of tephra bands and top of the debris-rich ice layer, if present): 1, 5, 6, 7, 8.
OBJECTIVE ONE - VELOCITY DISTRIBUTION IN ICE
(1) Determine surface velocity of glacier at a number of sites (at the 100m site and
along transect)
(2) Determine thickness and surface slopes at these sites.
Equipment
differential geopositioning system
electronic distance measurer
water pressure transducer
Repeat (daily depending on velocity) surveying of strain network will allow
surface velocity pattern to be measured. This can be related to water
pressures if short-term variability is observed. Ice deformation can be
estimated with data on ice thickness (borehole flooding), surface slope and
longditudinal velocity profile. This would be best done along a flowline
(line of maximum down-glacier gradient). Before and after borehole lengths
will allow testing of deformation component calculations.
Output
How fast is the ice moving, how thick is it?
OBJECTIVE TWO - MASS BALANCE
(1) Determine ablation, incoming solar radiation and precipitation rates during our
stay.
(2) Collect meteorological data to allow testing of energy balance
model against measured ablation data.
(3) Determine spatial variability of albedo.
(4) Determine micrometeorological parameters needed by model, eg roughness
length.
Equipment
SOC meteorological station (automated)
raingauge (automated)
radiometer and anemometer (hand held)
Ablation stakes
Meteorological station and raingauge to be set up at start of stay and
data logging started. Ablation stakes to be set over a variety of surface
types. Daily/weekly ablation values to be recorded. Radiometer used to
determine albedo over the range of surface types.
Output
Tested energy balance model for ablation calculations.
Precipation and incoming solar radiation record to compare with glacier velocity
changes.
OBJECTIVE THREE – GEOMORPHOLOGICAL MAPPING
(1) Determine past glacial limits – Little ice age, recent surge
(2) Reconstruct past subglacial behaviour
Equipment
Spades
EDM
Ground-truth the limits shown on airphoto. Plot in the 1999 ice limit. Choose a
particularly interesting area of subglacial bedforms for investigation: a)
height/length/width, b) type (with core/without core), c) fabric (if possible).
Output
What are the past dimensions of the glacier, and what was the past subglacial
behaviour of the glacier?
OBJECTIVE FOUR – TEPHRA SAMPLING
(1) Determine past glacier flow rate.
Equipment
Trowel and sample bottles
Sample different tephra bands on the ice surface.
Output
How fast is the ice moving on the long term?
OBJECTIVE FIVE – THICKNESS OF SUBGLACIAL SEDIMENT
(1) Determine thickness and variability of subglacial sediment.
Equipment
penetrometer
Spatial variability of penetration depth can be used as an index of subglacial sediment
thickness (assuming no large obstacles).
If the layer is relatively similar at 100m site then attempt a tranmsect back down the
glacier
Output
Map of the thickness of the subglacial sediment.
OBJECTIVE SIX - VELOCITY DISTRIBUTION IN SUBGLACIAL
SEDIMENT
(1) Determine proportion of velocity which is basal slip.
(2) Determine whether subglacial sediment is deforming and, if so, to what
depth.
Equipment
drag spools
ploughmeter
subglacial tilt cells
Drag spools should allow some estimate of basal velocity component to be made.
Ploughmeter will indicate whether there is any basal motion. Tilt cells
should give some indication of the depth of deformation and its profile.
Both can be related to water pressures.
Output
What proportion of the glacier's velocity is due to basal slip? How much
of the subglacial sediment is deforming?
OBJECTIVE SEVEN - SUBGLACIAL HYDROLOGY
(1) Determine water pressures and their temporal and spatial variability.
(2) Determine the rate of subglacial water flow.
Equipment
water pressure transducer
salt injection equipment
The pressure transducers will tell us the pressure of the subglacial
hydrological system assuming connection is made. They will also show
whether this system is affected by diurnal or rainfall-related variability.
This information should be gathered very early on because it will guide the
sampling strategies needed in the other objectives. The pattern of water
pressures can be interpreted in terms of drainage pattern. The pressure
transducers can also tell us ice thickness if the borehole is flooded.
Salt injection and tracing will yield estimates of water velocity. This
can be related to piezometric surface (pressure transducers) and (if a
number of datasets are available for the same site) Darcy's Law can be
tested.
Output
What are the water pressures and how do they vary temporally and spatially?
Are they related to subglacial water flow and (via the other objectives)
glacier
velocity and sediment deformation?
OBJECTIVE EIGHT - SUBGLACIAL SAMPLING
(1) Obtain in situ samples of the sediment.
Equipment
Zurich, Akkerman and piston corers
Subglacial sediments to be taken at a variety of sites according to ease
of extraction.
Output
What are its rheological characteristics.
OBJECTIVE NINE - PROGLACIAL SAMPLING
(1) Obtain samples from the foreland of geotechnical testing in the triaxial and the
deformation tank.
(2) Obtain micromorphology samples.
Equipment
“Biscuit Tin” sample boxes
Kubiena tins
The bulk samples will be taken at sites with different grain sizes. At the same sites
micromorphological samples will be taken, as well as at a number of locations within
drumlins. Similar locations within a lineation, flute and drumlin.
Output
What are its rheological characteristics of the proglacial material, is it the same as the
subglacial. How do the rheological properties vary with grain size. What is the
behaviour of the grains on a microscale, rotation or grain fracturing? Microscale
evidence for deformation? How does microfabric and microstructures vary through
subglacial bedforms of different scales? How do the microstructures in the field
compare with those from the deformation tank?
OBJECTIVE TEN – VISUALISATION
(1) Borehole camera, used to record tephra layers in the borehole and record the level
of the debris-rich basal ice layer (if any).
(2) Panoramas, used to in the multi-media visualisation of the site for the “Public
Awareness of Science” aspect of the project (web pages, etc).
Equipment
Borehole camera
Digital camera and tripod
Hand held GPS
Output
Still and moving digital images