THE FATE OF ICE CAVES IN NORTH-WESTERN CANADA AS
CLIMATE WARMS: WHAT WILL WE LOSE?
Charles J Yonge PhD
Alberta Speleological Society
Yonge Cave & Karst Consulting Inc.,
1009 Larch Place,
Canmore, T1W 1S7 AB, Canada
chas-karst@telus.net
Abstract
A number of ice cave sites in the northwestern Canada region are exhibiting a loss of perennial ice apparently
resulting from the current climate warming trend. Three of the six sites in this study show such ice loss; with one
further cave unproven as it is a new site. In addition, the fate of ice from some of the caves in earlier studies remains
unknown as they have not been revisited - generally because of their remote locations. In an effort to understand the
systematics of perennial ice in caves, three types of ice cave have been suggested: cold trap, cold zone and
permafrost (Yonge and MacDonald, 2014).
Why should we be worried about the condition of these ice caves? Ice caves in their own right are very beautiful as
shown in a number of the accompanying photographs. But beyond the esthetics, cave ice may also be an important
proxy climate record, monitoring the very climate that appears to be changing quite rapidly. Study of cave ice is
very important if we are to fully understand the implications of what the ice is telling us. Thus, in this study we
continued the attempt to unravel climate using the stable isotopes of oxygen and hydrogen (δ18O and δ2H), now
comparing this data to that collected in earlier work (Yonge & MacDonald, 1999, Yonge & MacDonald, 2006).
Where possible, we have tried to understand the chronology of ice, collecting trapped organic material for 14C
dating.
Plate1 The Booming Ice Chasm – a large
newly discovered cold trap cave in the
Crowsnest Pass, Alberta, Canada
RCGS – Ice Caves
Introduction
A number of studies of perennial ice in caves have been undertaken (see e.g. Ford and Williams, 2007, Yonge
2004); but there are relatively few studies employing stable isotopes and these are confined to Europe (Kern et al.,
2011; Persoiu1 and A. Pazdur, 2011; Holmlund et al., 2005; Racovita & Onac, 2000; Lauritzen 1996) and North
America (Lacelle et al., 2009; Yonge & MacDonald, 1999, Yonge & MacDonald, 2006; Martin & Quinn, 1991;
Marshall & Brown, 1974). With the current interest in climate change, a wealth of studies has accumulated on polar
(e.g. Jouzel & Masson-Delmotte, 2010; Johnsen et al., 2001) and cordilleran (e.g. Thompson & Davis, 2005) ice
cores.
While ice cores deal with the direct precipitation of snow and the subsequent modification of the resulting layers by
various physical processes, the mechanisms of ice formation in caves, being confined, can be quite different and
may require an alternative interpretation (e.g. Yonge & MacDonald, 2014; Lacelle et al., 2009 and Yonge &
MacDonald, 1999). Here we apply the model of Yonge & MacDonald (2014) identifying three possible ice cave
types (and combinations of these where cave systems are complex). We have examined caves which are dominated
by a cold zone close to the entrance (Cold Zone type); those in Permafrost (Permafrost type) and pit caves where
cold air and snow is trapped (Cold Trap type).
While we have examined fourteen caves from the region in previous studies, in this study five new sites and one
repeat site have been added. In the latter case, it was possible to compare records from 1989-1992 to our collection
in 2014. All sites exemplify classic perennial ice features: massive ice, hoar frost, ice stalagmites & stalactites and
extrusion ice (see e.g. Yonge, 2004).
Stable isotopes measured on the ice (δ18O and δ2H) assist in understanding the origin of the freezing moisture,
whether from direct snow (cold trap), moist summer air (permafrost) or humid air within the cave (cold zone).
Delineating the complex systematics of cave ice formation is vitally important if it is to be used (or rejected) as a
proxy climate record.
Methodology
Field Sites
While stable isotope data of perennial ice was acquired from 6 cave sites, which from south to north comprise:
Bisaro Anima, AB (49o 36’ N, 115o 09’ W; elevation 2400m), Booming Ice Chasm, AB (49o 37’ N, 114o 38’ W;
elevation 2200m), Plateau Mountain Ice Cave, AB (50o 20’ N, 114o 31’ W; elevation 2250m), Canyon Creek Ice
Cave, AB (50o 54’ N, 114o 47’ W; elevation 1775m), Ice Trap, AB (53o 03’ N, 114o 39’ W; elevation 2390m) and
Grotte Valerie, Nahanni, NWT (61o 19’ N, 124o 10’ W; elevation 700m).
The cave types investigated appear to be:
• Bisaro Anima:
Cold Trap
• Booming Ice Chasm:
Cold Trap
• Plateau Mtn. Ice Cave:
Permafrost
• Canyon Creek Ice Cave: Cold Zone
• Ice Trap:
Permafrost/cold zone
• Grotte Valerie, NWT:
Permafrost/cold zone
All are from the east side of the Great Divide (see Results and Discussion below for details).
Sample Collection
We drilled out massive ice (floor and stratified) using an ice climbing screw. Where the ice was stratified, we
sampled visually obvious ice layers sequentially, then transferring the samples to 30ml glass bottles with the ice
screw carefully dried after each extraction. We collected all other ice by crumbling the ice into the bottles with
seepage water collected by direct dripping into the sample vials.
RCGS – Ice Caves
Analysis
We had the samples analyzed at the Calgary University Stable Isotope Laboratory: δ18O and δ2H are expressed in
per mille (‰) against the V-SMOW standard as:
δ = (Rsample/Rstandard - 1) 103 (‰)
(1)
Rsample and Rstandard are the ratios of 18O/16O and 2H/1H in the sample and standard respectively. Precision is +/-0.1%o
on δ18O and 0.7%o on δ2H %o.
Because concentrations of the heavy isotopes (18O and 2H) are small compared to the common 16O and 1H, use of the
δ-value allows terrestrial samples to be compared to (homogeneous) ocean water yielding sensible numbers. The
Vienna Standard Mean Ocean Water (V-SMOW) has a δ-value of 0 ‰ and all terrestrial sample tend to have
negative values (i.e. during the distillation process in the hydrological cycle, the lighter isotopes with a lower vapour
pressure are picked up in clouds preferentially).
Results
Global precipitation world-wide, while negative compared to ocean water, falls on or close to the Global Meteoric
Water Line – GMWL (see blue line on figure 1 – Craig, 1961; Dansgaard, 1964), which yields:
δ2H = 8δ18O +10 (‰)
(2)
Some minor modifications of this line have been introduced later (Rozanski et al., 1993) but do not affect our
arguments presented here. Positions on the line generally relate to site temperature, where the lowest temperature is
associated with the lowest δ-values (figures 1 and 2).
Figure 1: Hydrogen & oxygen
stable Isotope data for the 6
caves in this study compared to
the GMWL.
RCGS – Ice Caves
Isotopic data for 19 caves - comprising those of Yonge and MacDonald (2006) and the 6 ice caves in this study - is
presented in Figure 2. Data from ice caves on each side of the Great American Divide fall on two distinct Regional
Meteoric Water Lines (RMWL - figure 2 and Table 1):
δ2H = 8.0 δ18O + 4.1 (‰) East (3)
δ2H = 8.0 δ18O + 12.8 (‰) West (4)
Figure 2
The δ18O - δ2H of ice
from 19 North
American ice caves
from East (<250km
from coast) and West
(>750km from coast)
of the Divide (data
from Yonge and
MacDonald, 2006 and
this study).
And in addition, despite the universality of
the GMWL and the RMWL here in
Western Canda, it has long been
recognized that Local Meteoric Water
Lines (LMWL) exist at each site. With
lower slopes, these lines cross the GMWL
with their means, representing mean
annual temperature, plotting close to the
GMWL.
LMWL’s are presented in table 1 and
figure 3 for the caves in this study; all are
east of the Great Divide and all exhibit
slopes less than 8, especially Plateau
Mountain Ice Cave (at 4.2) discussed in a
later section.
Figure 4 presents the average deuterium
excess d-excess (‰) for each of the 19
caves of Figure 1. This is acquired by
forcing the LMWLs to a slope of 8
yielding the d-excess at intercept. The
figure is another, effective way of
expressing differences in the two regions
where the d-excess unambiguously splits
into two fields, each representing the east
and west of the Great Divide. The dexcess is also a way of expressing δ18O in
terms of δ2H.
Ice Cave
LMWL
Regression
δ2H = N/A
R2 = 0.04
2
18
δ H = 6.7δ O -19.0
R2 = 0.97
2
18
δ H = 6.9δ O -14.4
R2 = 0.97
2
18
δ H = 4.2δ O -62.7
R2 = 0.98
2
18
δ H = 6.9δ O –11.0
R2 = 0.94
2
18
δ H = 6.9δ O –11.0
R2 = 0.99
___________________________________________
_
Regional
RMWL (slopes forced to 8)
East of Divide
δ2H = 8.0δ18O +4.1
R2 = 0.96
2
18
West of Divide
δ H = 8.0δ O +12.8
R2 = 0.90
Combined data of Yonge and MacDonald (2006) &
this study.
Grotte Valerie
Ice Trap
Canyon Creek
Plateau Mountain
Boom. Ice Chasm
Bisaro SGIP
Table 1 Local & Regional Meteoric Water
Lines
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Figure 3
Regional Meteoric
Water Lines
(RMWL) for the
caves in this study
d-excess = 8.0 δ18O + δ2H
Figure 4
The d-excess versus distance from the Pacific coast for 19 North American ice
caves (Circled are fields for caves <250km and >750km).
Discussion
Meteoric Water Lines and Ice Caves
Figures 2 and 4 show delineated fields relating to two RMWLs clearly defined by the d-deficiency. The ice caves
east of the Great Divide on average yield a lower d-excess (4.1%o), which appears to be a combination of a drier,
more evaporative climate there and a greater tendency to precipitate snow and hoar frost in the caves. An
evaporative climate tends to yield precipitation which falls along a model slope of 4 below the GMWL, but also the
direct sublimation of cloud vapour to snow and cave hoar yields values below the GMWL (Plateau Mountain Ice
Cave – figure 3 – being a good example). The caves close to the coast are in high humidity regimes where rain is
more dominant and the resulting ice (mainly of snow in cold traps) tends to plot close to the GMWL (intercept of
+12.8%o). The LMWLs in this study (table 1) yield slopes around 8 or less, which supports the argument above of a
drier, colder climate on the east side of the Divide leading to lower humidity and a greater proportion of solid
precipitation. Note that in figure 2 the easterly caves tend to plot with more negative δ-values on the Water Lines
indicative of the cooler climate on that side of the Divide.
We now examine the ice caves in more detail, starting with the cold trap caves (Bisaro and Booming Ice Chasm),
followed by the permafrost caves (Plateau Mountain, Grotte Valerie and Ice Trap, ending with the cold zone cave
(Canyon Creek).
Cold Trap Caves:
Bisaro (Superman’s Glittering Ice Palace) and Booming Ice Chasm
Cold traps occur where there is little through movement of air within a pit-like cave. Cold winter air sinks into the
cave, generally through a bottleneck, and displaces warmer air within. Snow falling through or blowing into the
entrance aids the cold trap conditions providing an environment for perennial ice. During the summer, buoyant
warm air cannot get into the cave other than by eddy currents and the cave maintains a temperature lower than the
mean annual temperature. Thus, the formation of ice in cold trap caves appears likely to resemble glacier ice by
direct accumulation of snow; in some cases where ice flow has been demonstrated within the cave it is referred to as
a Glacier Cave (Holmlund et al., 2005; MacDonald, 1994; Yonge and MacDonald, 2014).
RCGS – Ice Caves
Figure 5
Figure 6 δ2H Variation within stratified
ice Bisaro SGIP
Bisaro’s Superman’s Glittering Ice Palace
(SGIP) received only a preliminary investigation
in the summer of 2014 (figures 5 and 6). The
Bisaro area is in a remote location, currently
accessible by helicopter. SGIP is however a
Winter air exchange
classic cold trap cave with winter air and
occasional blowing snow flowing down and
being trapped in the lower chamber, which forms
a stratified ice capped by residual snow. Little
can be said about the cave ice data except that it conforms to that which is expected for a cave to the east of the
Great Divide (figure 3). The stratified ice profile shows a general warming trend ending with the residual snow on
top of the mound, δ2H ranging from -142 to -113 ‰. However, we do not know the age of the ice although from
experience of such small ice caves, it is likely to be young – measured in decades.
Figure 7 The Bisaro Plateau near Fernie BC
showing the location of Bisaro SGIP
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Plate 2 Booming Ice Chasm – a view in a side
passage located on the map below
Figure 8 Booming Ice Chasm
The Booming Ice Chasm is essentially a
massive shaft 140m deep (Plates 1, 2 and
Figure 8).
Ice Sampling:
Stratified
Icefall
Hoar Frost
Figure 9 shows the results for a small
stratified ice mass (figure 8 shows the
sample location). While there is a trend
toward increasingly depleted 2H towards
the present day (lower δ-values), they are
nonetheless well within those expected for
the area (Figure 1), having similar
Figure 9 Booming Ice Chasm
Hoar Frost
RCGS – Ice Caves
Ice Falls
characteristics to the other cold trap cave, Bisaro SGIP (Figure 3).
Included on Figure 9 are the average values for the massive ice falls
(Plates 1, 2 and map) and hoar frost taken from the walls at the entrance
and bottom of the Main Shaft. One interpretation for the stratified ice
would be a varying mixture of incoming, refrozen snow melt and the hoar
frost. The latter is likely moist summer air enriched in the heavy isotopes
which freezes on the walls and eventually falling to the floor (see section
on Permafrost ice cave types). If this mixing is real, then a climatic
interpretation could be that a greater proportion of hoar ice in the ice mass
implies a warmer climatic regime. The stratigraphy shows a cooling
toward the present day but the rate is not known with undated ice.
Permafrost Caves: Plateau Mountain Ice Cave, Grotte Valerie and the Ice Trap
Permafrost caves have been discussed by Yonge and MacDonald (1999), where an isotopic model was developed to
explain the surprisingly high δ−values and low d-excess of cave ice when compared to snow or average
precipitation. The premise of the model is that warm, moist
air enters the cave in summer where it is forced to freeze
on the permafrost walls at ~0oC. This vapour-solid
sublimation process leads to a large fractionation of the
isotopes, with higher δ−values in the ice (hoar frost). In
addition the warm summer vapour source will have
relatively high δ−values associated with the higher
temperatures outside. Thus the combined outcome is a high
δ−value in the hoar relative to average precipitation.
Figure 10 - from Yonge and MacDonald, 2013 - shows the
results from Ice Chest, which is only a few hundred metres
2
west of the Booming Ice Chasm, but is nevertheless within
Figure 10 δ H versus distance from the
the mountain permafrost zone. The hoar ice here has
entrance of Ice Chest, Alberta (Permafrost
similar δ−values to the massive ice in the cave (derived
Type). After Yonge & MacDonald, 1999.
from falling hoar), but the latter declines somewhat as the
entrance is approached, increasingly affected by an added lower δ−value of seepage water derived from snowmelt.
Plate3 Sheep residing in patterned
ground on Plateau Mountain
Plate 4 Looking out of the entrance of
Plateau Mountain Ice Cave
RCGS – Ice Caves
Plateau Mountain Ice Cave is in
the unique ecological reserve of
Plateau Mountain, an example of
relict alpine permafrost from the
Late Wisconsin glaciation. The flat
mountain top was not glaciated
during the Late Pleistocene and its
summit permafrost is not yet in
equilibrium with current climate.
The surface exhibits patterned
ground and thermokarst resulting
from melting of ice wedges formed
beneath stony borders during a
colder climate (plate 3). The slopes
of Plateau Mountain show very
well developed block slopes (view
in plate 4), in contrast to the rocky mountain
sides seen elsewhere in the adjacent Rockies.
At the northern end of the mountain, the >
400m Plateau Mountain Ice Cave penetrates
into the surface of the relict permafrost with
temperature decreasing with depth.
Plateau Mountain Ice Cave was mapped
during this study as no good survey had
previously existed (Figure 11). While the map
was almost completed, a couple of high-level
fissure leads remain to be explored just before
entering the large main chamber.
Figure
Plate 5 Hoar ice in the NW gallery
of Plateau Mountain Ice Cave with
detail below.
The few data of samples collected from the two western galleries in Plateau Mountain Ice Cave (PMIC) show an
interesting local meteoric water line (LMWL) with slope much lower than all of the caves studied here (Table 1 &
Figure 3) and those previously encountered (Yonge and MacDonald, 2013):
δ2H = 4.2δ18O -62.7
R2 = 0.98
(5)
The most depleted sample – approximately lying on the GMWL - came from a pool in the ice “streamway” in the
SW gallery. It appears to represent an end member and may be derived from drip water, i.e. an average of
precipitation at the site. All of the other samples are hoar frost (Plate 5) and they trend away from the GMWL along
an apparent mixing line of slope 4.2 with increasing d-excess. Figure 13 shows what happens if we freeze vapour
derived from a water body of GMWL composition. At say 10oC, water with a d-excess of +10 ‰ (i.e. on the
GMWL) forms a vapour at +14 ‰, but condenses back at 0oC with a d-excess of +3.0 ‰ (or if derived from 0oC
vapour -+1.2 ‰).
The middle 3 Plateau Mountain samples have an average dexcess of +5.0 ‰ and the furthest right -5.9 ‰ (figure 12).
While the latter seems too depleted for the model, we would
expect a variety of air masses entering the cave whose
Figure 12 Isotope
data for Plateau
Mountain Ice Cave
and Grotte Valerie
Figure 13 The depletion of d-Excess when
external vapour is forced to freeze within
an ice cave at 0oC
RCGS – Ice Caves
composition could vary considerably, so the model is only a guide. Another consideration is that evaporated water
bodies evolve along model slopes of 4 (Dansgaard, 1964), close to what we have here. However, there is no liquid
water evident so this shouldn’t act as a mechanism. However the ice in the cave is retreating and there is much
evidence of melting and refreezing of the hoar – perhaps there is an evaporative component, but likely to be very
small.
Regarding the fate of the ice, the managers of the site (Alberta Environment and Sustainable Development) have
very restrictive access policy for its protection. Therefore a good understanding of the ice formations and what the
future holds is very important if the site is to be protected. It seems that while restricting visitors will help, it may be
a losing battle against current climate warming and the ice will eventually disappear along with the mountain
permafrost. Core samples from the massive floor ice may assist in our understanding, perhaps showing an increased
evaporative component?
Figure 14 Grotte Valerie, Nahanni, NWT with sample locations
Plate 6 Grotte Valerie – Great Ice
Passage. Photo: Sylvain Foster
Grotte Valerie in the Nahanni, NWT is also
a permafrost cave in a rather remote
location. A very few ice samples (4), hoar
frost ice core were collected by a colleague
who was guiding some visitors there in the
summer of 2014 (Figures 12, 14 and plates 6
and 7). The samples clearly lie off the
GMWL with d-excesses of +0.8 ‰ (ice
cores) and -4.4 ‰ (hoar). In agreement of
the model in figure 13, we see a much
depleted hoar but the ice cores staying
within the model boundaries. However,
these are the first samples collected from
such an easterly (and northern) ice cave, and
it’s likely that the LMWL here lies
somewhere to the right of the GMWL giving
these rather low values (i.e. starting at the
LMWL, with the d-excess < 10‰ will yield
cave hoar ice lower values than modelled).
It also suggests that a detailed sampling of
the ice cores might give climate information,
especially as they are in the vicinity of a
number of Dall Sheep that had fallen down
an ice slope in the last 2,000 years – some
are trapped under the ice, allowing dating,
with the two cores being taken from the
lowest depth of the banded ice (Figures 14 &
15).
Figure 15 shows the dynamics of air
movement through the cave in summer.
Warm air can be drawn in through the west
entrance despite being higher (albeit only
RCGS – Ice Caves
40m) because cold air is draining from the lower, permafrozen entrance. This moist summer air then is forced to
condense as hoar at descending temperatures 0 to -3oC. The descending temperature is also a function of the cold
zone effect (see next section).
Clearly, this cave is worthy of further study, both to further understand the systematics of the ice formation and then
to interpret climate from the ice cores based on the ice systematics. Dating of the sheep remains would be important
for timelines.
Figure 15 A schematic of Grotte Valerie, Nahanni, NWT. After Ford & Williams 2007
Plate 7 Grotte Valerie - clockwise: collecting hoar ice/descending ice above the sheep
remains/sampling the ice from previous/ice stalagmite formed on Dall sheep skull. Photos: Sylvain Foster
RCGS – Ice Caves
Plate 8 Large Passage in the Ice Trap. Note
fault slickensides on ceiling Photo: Greg Horne
Plate 9 The Ice Trap showing “kitty litter” cryosediments – inset for detail. Photos: Greg Horne
The Ice Trap is another
remarkable ice cave in
Plate 10
a remote location up
“Kitty Litter”
the Snaring River in
containing
Jasper National Park. A
extrusion
high proportion of the
ice. Photo:
cave is in large, faulted
Lee Hollis
passageways (Plate 8).
The majority of the
>3.5km system appears
to vary from -2oC to -7
o
C, with relative
humidity 27-95%
(Figure 16) and is thus
within the mountain
permafrost. The cave is thus unusually dry with dusty
(cryoturbated) sediments (nicknamed “kitty litter”)
indicative of its cold and arid environment (Plate 9).
Although generally dry, in one area we were able to
collect extrusion ice within the kitty litter (Plate 10), which
shows cryoturbation in process – the freezing and
extrusion process crumbling the sediments. The δ-values
are consistent with sublimation of cave vapour discussed
earlier in this section.
Plate 11 Ancient marmot midden in Ice
Trap. Photo: Greg Horne
Figure 16
Temperature & Relative Humidity at the
Ice Tongue from the 7 May to 7 June, 2005
The cave promises interesting Holocene climatic
information. For example, guano taken from a nest
of mortified marmots was 14C dated to 9,560 +/- 40
years; a most surprising result considering the
freshness of the site (Plate 11).
Date
RCGS – Ice Caves
Figure 17 shows a rough map of the cave
superimposed on a Google Earth image of the high
alpine environment (entrance at 2,350m). Access to
the cave is either by helicopter or a 2-day, high
alpine traverse from Jasper. We were fortunate to
access the cave for sampling in the summer of 2014
by sharing a helicopter assigned to fire duty.
Ice Wave
Cave Entrance
Ice Tongue
Figure 17
Ice Trap Cave on Google Earth. Inset shows
the north-facing entrance area (Photo: Greg Horne).
The Ice Trap contains two areas of massive ice (Figure 17), the Ice Wave and Ice Tongue (Plates 12 and 13).
Single core samples were taken from each of the two sections of the Ice Wave (Upper & Lower). These gave the
lowest (most-depleted) δ-values from the cave, the Upper more depleted than the Lower, and almost the most
depleted in all of the studies (Figures 2
and 18). In fact, low δ-values from a
previous study (Yonge and MacDonald
(2013) from Canyon Creek Ice Cave,
thought to be due to a cold zone: Canyon
Creek in this context is discussed at
length in the following section, but some
comments are useful here.
Cold Zones result as humid air flows out
of a cave and, on approaching the
entrance, generally meets a less humid
environment, condenses and cools as
latent heat is taken from the walls of the
Plate 12 Upper section of the cave (note that in Figure 16, relative
Wave. The white powder is
humidity - admittedly measured at the
calcite precipitating from the ice
Ice Tongue - exhibit values <100% thus
as it sublimes. Photo: Greg Horne
allowing precipitation by sublimation). In
cold region caves, the cold zone can be
reduced to <0oC thus forming ice there.
As the cave vapour moves towards the entrance and precipitates, it becomes steadily more depleted isotopically by
the Rayleigh Distillation mechanism. Interestingly, the Upper Ice Wave (δ2H = -196‰) is more depleted than the
Lower Ice Wave (δ2H = -184‰), which is to be expected if an entrance lies above the Upper. At this point there is a
boulder choke in the cave, which is likely a collapsed entrance. Of course, another alternative is that the ice is old
and dates back to an earlier, cooler climatic time. Unfortunately, we do not see any organic material to date here, so
the age of this ice is unknown.
RCGS – Ice Caves
Plate 13 The Ice Tongue.
Plate 13 shows the spectacular Ice Tongue
whose faceted morphology suggests ice
retreat via sublimation. While on previous
visits 9 years earlier, we thought that this
represented an ice-filled passage in retreat,
our summer visit of 2014 showed a great
deal of change. We noted a small, drafting
hole to the right of the Tongue, which
allowed access to its far side (see left of
Plate 14). Once through into this hitherto
inaccessible area, it was evident that retreat
is occurring on both sides and that far from
an ice-filled passage, we were dealing
more with an ice plug. Furthermore, on
the far side of the Tongue, we entered a
wetter area of dripping icicles, likely
snowmelt from outside and another
blocked entrance. Clearly the ice is rapidly
Photo: Greg Horne.
Plate 14 Back of the Ice Tongue showing sampling sites. Photos:
Packrat guano 14C
date locations
Greg Horne
disappearing and this may be our
last visit before the ice is gone.
Importantly, we have measured
two 14C dates on packrat guano –
inset of Plate 14 – shows the
base of the ice formation to be
2,170+/-30 and 1,120+/-30 years
in an upper layer (Plate 14).
Unfortunately we could not find
any organic material higher in
the ice strata for dating.
We further sampled the stratified
ice for stable isotopes, focusing
on the main layers seen (Plates
14 & 15), with results shown in
Figures 18 and 19.
Recent breach of the Ice allowing
access to the stratified ice wall
Plate 15 Ice core sampling
from the back of the Ice
Tongue. Photo: Greg Horne
RCGS – Ice Caves
Figure 18 Stable isotope
data for Ice Trap Cave
Figure 19
d-Excess and δ2H for stratified ice in Ice Trap
Cave. The d-Excess expresses the coupling between δ18O
& δ2H. Top and bottom dates are extrapolated.
11 years
1,210 years
Average
dExcess
for all
cave ice
2,170
Base of Ice 2,472
Data from the ice wall are shown in
Figure 19 with the two offset sampling
profiles (Figure 18) combined. As
reported above, we currently have a
base 14C date for the ice at 2,170 and a
medial date of 1,210 years. With
extrapolation, the whole mass appears to
date from 2,472 years to the present day.
However to make a climatic
interpretation, we need to understand
which type of ice emplacement
mechanism we have? As discussed
above, a cold zone is operating but
aided by an added permafrost
component. And the cold zones at the
Wave and Tongue appear to be recent
via post-glacial breaching of the cave
system. At the Tongue, the wall of ice
appears to reflect this with the cold zone
commencing 2,472 years ago and
continuing to the present day.
Figure 20 illustrates the difficulty of climate interpretation without a much denser data record from Ice Trap.
Both the d-excess and δ2H values show opposite transitions at the beginning of the MWP (Medieval Warm
Period)mand during the LIA (Little Ice Age). One scenario this that low d-excess and higher δ2H seen mainly at
600AD and 1700AD suggest domination by permafrost hoar, whereas the opposite (200AD and 1190AD) is
indicative a cold zone domination in a warmer climate. This also fits with the general cooling of climate over the
Holocene (Esper et al, 2012 and Yonge, 2012). An alternative scenario is that the permafrost/cold zone mechanism
at the cave has remained essentially the same over the 2.47ka period of ice accumulation and that high d-excess and
low δ2H are associated with a colder and less humid outside environment. In fact, there appears to be an overall
trend in time towards enriched δ2H (i.e. a greater participation of warmer summer air and thus a warming trend –
previous section). The first scenario fits better with the Medieval Warm Period/Little Ice Age model with the current
“Hockey Stick” current temperature rise; more stable isotope and 14C data are required to establish it.
Figure 20
Stable isotope climate record from Ice Trap Cave compared to reconstructed global
temperatures (upper plot) and the normalized temperature record for SW Canada (lower green plot).
RCGS – Ice Caves
Figure 20 Schematic of a
cave environment which
generates a cold zone. From
Luetscher and Jeannin, 2004
Cold Zone Caves
Cold zones in caves result from evaporative cooling at the cave walls. This
condition generally occurs close to the cave entrance where the relative
humidity drops from 100% deep in the cave to <100% toward the outside. The
condition is also seasonal in that summer moisture condensation can transfer
energy to the cave surfaces - increasing temperatures –and so it is during the
fall and winter when the cold zone is maintained. In some cases the cold zone
supports perennial ice, as we discuss here.
Wigley and
Brown (1976)
have modelled
cave temperature
and humidity
yielding a
relaxation length
(the cold zone is
scaled by airflow
rate and passage
diameter):
Figure 21 A schematic of the cold zone mechanism
xo = 100D1.2V 0.2
(6)
Where D is the passage diameter, V is the flow
rate and cold zone xo is in metres.
Plate 16
Cold zone
in Castleguard cave
where xo = 200m.
Canada’s longest cave, Castleguard contains a
classic cold zone cave with ice extending around
400m, but the ice is not perennial (Plate 16).
However here, we examine Canyon Creek Ice
Cave, a rather low altitude cave which supports a
(retreating) cold zone. We also have data over 20
years apart allowing us to study recent changes to
the ice.
Plate 17 Stratified Ice in Canyon
Creek Ice Cave 152m from the
entrance in 2014 – Photo: Nick Vieira
While Canyon Creel Ice Cave is a classic cold
zone cave, we note that some permafrost caves in
this study with significant air movement (Ice Trap
and Grotte Valerie) act in some way like cold zone
caves (e.g. Figure 15). However, in these cases the
cold zone is aided or maintained by the presence
of remnant mountain permafrost (see discussion in
the previous section).
The cold zone currently extends from around 50m
to 180m from the entrance (xo=130m); which with
D = 1.2m and V = 1.3m/s further into the cave is
what would be predicted. However, the ice is
currently in retreat if compared to ice collections
taken from the summer of 1989 to early 1992
(MacDonald, 1994), although non-perennial ice is
still seen along the 130m relaxation zone (xo).
RCGS – Ice Caves
Figure 22 displays the δ2H of various ice types
versus distance from the cave entrance from our
previous study. Superimposed on the figure is a
vertical bar showing the range of the 2014 data; in
essence this data fits well with what was measured
over 20 years earlier.
Figures 23 and 24 show the stratified ice results for
the d-excess and δ2H at 56m (old data when ice
extended further towards the entrance) and 152m
(the current ice front). Note that when looking at
averages for the stratified ice at each of those
locations, shifts of both the d-excess (5.7 to 4.3 ‰)
and δ2H (-154 to -135 ‰) are seen. The latter
averages broadly indicate a Rayleigh distillation
mechanism which one would expect occurring
across the cold zone (x0). However, we see a great
variation in the stratified ice sequences, whereas if
the mechanism of ice emplacement was purely
Rayleigh distillation from a constant vapour source
(cave air), then there should be no
Figure 23 A plot of d-excess for stratified
ice for Canyon Creek Ice Cave. Old data is
from Yonge & MacDonald, 2014. See text
for green correlation lines.
Figure 24 A plot of stratified of ice
versus entrance distance for Canyon
Creek Ice Cave. Old data is from Yonge &
MacDonald, 2014. See text for green
correlation lines.
Figure 22 A plot of δ2H of ice
types versus entrance distance
for Canyon Creek Ice Cave (from
Yonge & MacDonald, 2014)
Stratified ice data range
from this study
variation. The variation
could be explained by
a mixing of a
groundwater
contribution to the ice
produced by
sublimation in the cold
zone and that the data
of Figure 22 represents
the degree of mixing,
pure mixing giving the
upper line and pure
Rayleigh giving the
lower.
In terms of climate
interpretation, we do
not yet have any dates
on this ice. However,
there is reason to
believe it is only in the
order of decades old.
First there is fresh
wood and occasional
human detritus trapped
in the ice. There are
also anecdotal accounts
of the ice almost completely disappearing in the recent past. Indeed, in
the early 80’s it was possible to get through the ice and access almost
600m of further passages in the back part of the cave (the total length of the cave is 727m). It is thus possible that we
are observing variations of a few years in the layers and that annual variations could be observed if closer sampling
was employed (visually obvious layers were sampled – Plate 18).
RCGS – Ice Caves
Plate 18 Sampling stratified Ice in
Canyon Creek Ice Cave 152m from the
entrance in 2014 – Photo: Nick Vieira
The d-excess and δ2H amplitudes are
greater in the earlier sampled ice, but
was sampled much closer to the
entrance (56m) than in this study
(152m) when the ice was more
extensive. The obvious implication is
that external factors such as summer
moisture and seepage modify the
Rayleigh generated ice the closer to the
entrance where there is more interaction
from outside sources. In any event, it
would be useful if the two records
showed correlated amplitudes with ice
layer, and while this is not obvious, we
have made some attempt (green lines on
figures 23 and 24). Having chosen the
negative swings on the δ2H plot, we
then see some correspondence in
positive peaks of the d-excess. If we
apply this to the opposite swings, we
again see correlated amplitudes (not
shown for clarity), giving us some assurance of being on the right track.
Bases on the above discussion, the climatic (or weather) interpretation is of more negative δ-values representing a
purer Rayleigh mechanism at work. This would occur when a longer transitional period (figure 21) exists in the
spring, securing a stable evaporitic environment along the cold zone, but one that did not melt the ice or not allow
ice formation i.e. a colder climate/weather regime. The converse (higher δ-values) implies a weakening of the
Rayleigh distillation and an influence of moist summer effects (air mass and seepage). Because of the kinetic nature
of the Raleigh + mixing system, only warmer and colder trends can be discerned and not actual temperatures. It
seems that the only system of the three ice types (cold trap, permafrost and cold zone) that would allow quantitative
temperatures to be assessed is the cold trap type.
Conclusions
Climatic Information – Cold Trap Caves: While there is much work to be done before stable isotopes of ice in
caves can be used as a proxy for recent climate change, this study has moved forward in the understanding of the ice
systematics. Prior work, of MacDonald (1994) and Holmlund et al (2005) has shown that cold trap caves with
extensive ice can act like underground glaciers allowing stable isotopes to be used as proxies for the precipitation
and hence temperature at the site. A word of caution
Temperature oC
though is that although cold traps can flow as glaciers
5
6.5
8
they are nonetheless constrained by the surrounding
rock mass, with the likelihood of seepage water
modifying the stratigraphy and muting the climate
signal. Also, ice caves are rarely just one type; one type
might dominate, but may have components of the other
types and may be modified by Rayleigh and/or
permafrost effects.
Figure 25 Variation of δ2H in stratified ice from Q5 &
Projects Cave (Yonge & MacDonald, 2013). Green line is
mean precipitation. Temperature from isotopic values is
based on Yonge et al (1985).
RCGS – Ice Caves
Figure 25 from Yonge and MacDonald 2013 shows the
δ2H variation for ice stratigraphy from two caves on
Vancouver Island, both of which contain substantial
(40m+) plugs of stratified ice. A moist coastal regime
dominates here with substantial inputs of both rain and
snow to the caves. Although the figure shows that ice
samples oscillate around mean precipitation δ-values,
Q5 yields a range generally higher than those for Projects Cave. Q5 has a stream running into the entrance in the
summer where the ice samples are found, so is likely more biased towards the heavier summer water. Projects Cave
shows lower values, but these cluster around mean precipitation at -92%o. It has no entrance stream and stratified
ice occurs almost 20m into the cave – a result of glacial movement perhaps. In this case we would have more
confidence in the record for Projects Cave, but would need to obtain data on its chronology as has been done at
Scarisoara Cave (Holmlund et al, 2005); the figure shows possible bi-annual (seasonal) variations in the δ−values.
Temperatures are based on a North American curve for average cave temperatures and δ2H values (Yonge et al,
1985). In the current study, few additional data were acquired on cold trap ice stratigraphy, but there is potential for
future work in the Booming Ice Chasm.
Permafrost and Cold Zone Caves: Because of the
kinetic nature of these ice emplacement mechanisms,
which depend on the duration and intensity of
external conditions - moist summer air in the case of
permafrost caves and transitional spring or fall
temperatures in the case of cold zone caves, only
relative temperature changes can be obtained.
However, in the above we note that temperature
trends in Cold Zone caves are opposite to Cold Trap
caves (and glaciers); i.e. that lower δ−values imply
higher temperatures and vice versa.
Plate 19 The ice tongue in
2005 (above) & 9 years later
(below)
A final word on cave ice stratigraphy is that much
more needs to be done. One area is in the dating of
the ice strata, which unfortunately incurs higher
costs than acquiring isotope data. We were able to
get some 14C dating done “in kind” through the
Royal Provincial Museum which has allowed us to
study some of the ice chronology and obtain some
real climatic interpretation (i.e. the section on Ice
Trap Cave).
Now while climatic interpretation is important from
ice cave stable isotope data, and which appears to
offer another tool for investigating recent climate
change, there is also the concern that the ice is disappearing at human scale rates. For example, in plate 14 we can
see the condition of the ice in 2014 along with a breech that allowed us access to the other side of the Ice Tongue.
Plate 19 shows a thinning of the Ice Tongue
Plate 20 Ice formations in The
from 2005 to 2014. It is thus evident that
Ice Cave, Wood Buffalo National
this ice will disappear, perhaps in another
Park – Photo Greg Horne
decade, especially as the ice plug has been
breached. This suggests some urgency in
studying ice caves generally.
At the 6th International Ice Caves
Workshop in Idaho, George Veni,
Executive Director of the National Cave and
Karst Research Institute in Carlsbad, New
Mexico, USA gave a clarion call to this
effect: Time, money, and melting ice:
Proposal for a cooperative study of the
world’s cave ice in a race against climate
change.”
RCGS – Ice Caves
Plate 21 Beautifully banded ice stratigraphy
in The Ice Cave, Wood Buffalo National Park –
Photo Greg Horne
In any event, we plan to continue our quest to document ice caves in the northwestern Canadian region. The Ice
Cave in Wood Buffalo National Park, Alberta is beautiful example (plates 20 and 21) that we would like to study. In
fact it was on the itinerary for this study, but forest fires last summer prevented access.
ACKNOWLEDGEMENTS
We are indebted to the Royal Canadian Geographical Society for their financial support of the project under their
Independent Research Grant. Without this support this project would not have been undertaken. We thank the Royal
Provincial Museum of Alberta for their support in getting the 14C dates for the ice without cost. The University of
Calgary made the stable isotope analyses, subsidizing the costs by 33%, for this we offer our appreciation. The
Alberta Speleological Society has been very supportive of the project, providing various volunteer field assistants
(especially Nick Vieira) on the way. Parks Canada, facilitated by Greg Horne, provided a helicopter between forest
fire duty for the work at Ice Trap; thanks for their flexibility and support.
RCGS – Ice Caves
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