59

Bulletin of Glaciological Research ,. (,**1) /3ῌ1*
ῌJapanese Society of Snow and Ice

Glacier variations of Hielo Patagónico Norte, Chile, for +3.././ῌ,**./*/
Masamu ANIYA
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki -*/ῌ2/1,, Japan(Received September ,3, ,**0; Revised manuscript accepted November ,,, ,**0)

Abstract
Variations of ,+ outlet glaciers of Hielo Patagónico Norte was elucidated for +3.././ῌ,**./,**/,
using various sources of remote sensing data including aerial surveys. Of ,+, +1 glaciers are found tobe calving more or less including one tidewater glacier, San Rafael. These calving glaciers wereclassiﬁed into three types, according to iceberg production; those with (+) many large icebergs, (,)
many small icebergs, and (-) no or few icebergs. These three types appear to indicate the stages inretreating in some calving glaciers. The type (+) indicates a rapid retreating stage, often accompanied with snout disintegration, which is preceded or followed by the stage (,) or (-). The largest
glacier of the HPN, Glaciar San Quintin has lost area ca. ,3 km, over the last 0* years, while Glaciar
Reicher retreated ca. 0 km. Among debris-covered glaciers, Glaciar Grosse started retreating actively
since the mid-+32*s, after forming a proglacial lake, while the neighbor glacier, Glaciar Exploradores
has been more or less stagnant. Although the general trend in the past 0* years is retreat, there weresome episodes of small advances. Glaciar San Rafael made advance between +330 and +333, which
was probably caused by topographic control of fjord width along with the inﬂuence of depth as well.

+.

Introduction

In light of the recent global warming, monitoring
glacier variation is important because existence andvariation of a glacier depend chieﬂy upon the climatic
factors such as temperature and precipitation. In orderto understand the world-wide trend and pattern ofthe glacier variation, monitoring the variation of thePatagonian glaciers is very important because the
Hielos Patagonicos (Patagonia Iceﬁeld) are located in
the Southern Hemisphere where land is scarce. Located at the southern tip of South America from latitude .0ῌ-*ῌ to /-ῌ-*ῌS along longitude 1-ῌῌ1.ῌW, Hielos
Patagonicos comprise two separate iceﬁelds now,
Hielo Patagónico Norte (HPN, or Northern Patagonia
Iceﬁeld, .,** km,) and Hielo Patagónico Sur (HPS, orSouthern Patagonia Iceﬁeld, +-*** km,). The combined area of +1,** km, makes the Patagonia Iceﬁeld
the largest temperate glacier body in the Southern
Hemisphere and one of the largest in the world.
Using various sources of remote sensing data, I
have been monitoring the variation of the Patagonian
glaciers, in particular, of the HPN since +3.././ (e. g.,
Aniya and Enomoto, +320; Aniya, +322, +33,, ,**+;
Wada and Aniya, +33/; Aniya and Wakao, +331).
After updating the variation to ,*** (Aniya, ,**+),
I have made an aerial survey of the HPN glaciers inNovember ,**+, December ,**-, July ,**., December,**., and August ,**/. Using survey photos from,**+, ,**- and ,**. (Dec.), I have updated the glaciervariation to ,**./,**/, which I report here together
with the analysis of variation characteristics and trends over the last 0* years.

,.

Study area

HPN is located between .0ῌ-*ῌ and .1ῌ-/ῌS and1-ῌ+*ῌ and 1.ῌ*/ῌW and is about +** km long northsouth and .*ῌ0* km wide with an area of .,** km,(Aniya, +322, Fig. +). It has the highest mountain in
Patagonia, Monte San Valentin (-3+* m) on the northeast corner of the iceﬁeld. Also in the middle of theiceﬁeld, Cerro (Co.) Arenales (--0/ m) looms above theiceﬁeld whose elevations range +***ῌ+/** m. To thesouth of Co. Arenales on the eastern peripheral of theiceﬁeld, there are a few mountains higher than -*** m.
From the iceﬁeld ,2 outlet glaciers ﬂow out in all
directions, and ,+ of them have been monitored byusing various sources of remote sensing data by
Aniya as mentioned above. Of the ,+ monitored glaciers, +1 are now calving glaciers including Glaciar
San Rafael, a tidewater glacier located at the lowest
latitude in the world. Glaciares San Quintin and San
Rafael are the two largest ones with the nearly equalarea of about 10* km,, which makes them the /th and60

Bulletin of Glaciological Research

Fig. +. Landsat image of Hielo Patagónico Norte(Northern Patagonia Iceﬁeld) and ,+ monitored
outlet glaciers (March ++, ,**+).

ever, due to the recent rapid recession, locating theterminus position on the oblique photographs onto
the vertical photographs has become very di$cult,because the recently exposed rock and/or water area
was covered with ice in the +31./1/ photographs. In
February of +331 and +332, the Chilean Servício Aerofotogramétrico (SAF) took another vertical aerial photographs over the HPN at a nominal scale of +: 1****.
With these photographs, the correlation of obliquephotographs could be done much more easily andaccurately than with the +31./1/ photographs. Consequently, the terminus positions at +320, +33+, +33/,+330, +333, and ,*** of some glaciers were interpreted
again and modiﬁed. Accordingly, for many glaciers
at many periods, I measured again the distance retreated and the area lost for each period. Therefore,
the previous statistics were revised along with updating to ,**./*/, and the new statistics in this paper
supersedes those of the previous publications (i.e.,Aniya, +33,; Wada and Aniya, +33/; Aniya and Wakao,+331; Aniya, ,**+). Although the many numbers changed,
the general and overall trends of variations were notsigniﬁcantly a#ected and the previous discussions arestill mostly valid.
Because it was easier and more accurate to compare the terminus position of oblique aerial photographs with the vertical remote sensing data of a closedate, I used Landsat ETMῌ image taken in March,*** (for Glaciar San Quintin, ASTER data of May,***) to locate the terminus position of November ,**+
(hereafter referred to as ,**+/*,), and the Landsat
ETMῌ image taken in April ,**- for December ,**(hereafter referred to as ,**-/*.) and December ,**.
(hereafter referred to as ,**./*/) positions.

0th largest glacier in South America.

..
-.

Results and discussion

Data and method

The ﬁrst coverage of the remote sensing data of
the HPN was the Trimetrogon aerial photographs
taken by the USA in +3.././. Next, from +31. to +31/,
the Chilean Instituto Geográﬁco Militar (IGM) took
vertical aerial photographs at a nominal scale of+: 0**** for topographic mapping at +: /**** with acontour interval of /* m. On the +: /**** topographic
map, the glacier margin is indicated; however, it was
found out that at some glaciers, the margin/terminus
position was wrongly delineated, which was often the
result of misinterpretation of the debris-covered areaand bare rocks, or water surface.
Since +32., Aniya has been making aerial surveysof the outlet glaciers of the HPN and the glaciervariation of ,+ outlet glaciers has been monitored. In
these works, oblique aerial photographs were interpreted and correlated with the +31./1/ vertical aerial
photographs, from which the terminus position wastransferred onto the +: /**** topographic map. How-

The revised and updated glacier variations arelisted in two types of measurements; (+) distance retreated (Table +), and (,) area lost (Table ,). For Glaciares Reicher and Gualas, formerly separated two
terminuses have become one due to large retreat andthey are listed as one after ,**,, while the terminus of
Glaciar Cachet separated into two, north snout andwest snout, due to large retreat. Figure , indicatesthe variation in area of the ,+ monitored glaciers for+3.././ῌ ,**./*/. Although the general trend of the
HPN glacier variations over the past 0* years is retreat, there were a few periods of advances at someglaciers, notably Glaciar San Rafael, during and after
the +33*s. Some of these advances were so small andwere probably episodic rather than sustained, whichwere probably detected only coincidentally by timingof the aerial surveys, such as those of Glaciares Piscis,
HPN- and León. Other advances such as Glacier Nef+33+ῌ3. and Glaciar Gualas +330ῌ33 and ,***ῌ*, were
ephemeral before large-scale retreat, which was pro-

61

Aniya

Table +. Glacier Variation of the Northern Patagonia Iceﬁeld, +3.././ῌ,***./*/ (Retreat in Distance (m), and the meanannual rate in parentheses)
Glacier Period+3./ῌ,**/*

Period+31/ῌ20+3./ῌ1/+320ῌ3++33+ῌ3.

+33.ῌ30

Northern Side
Grosse,0** (.-)/** (+1),/* (,-)

No substantial change,
but thinningca. ,** (01)ca. ,** (+**)

Western Side
Reicher: NE: SW-2** (0-)
0*** (+**),-/* (,+.),2* (,/),3/* (.3),0** (.-)
ca. .+/* (03),/* (,-)-/* (-,),,** (,**)+/*ῌ,** (-*ῌ.*)2/* (+1*), andnarrowed by -** (0*)+**ῌ+/* (,*ῌ-*)no substantial change
3**ῌ+/** (+3*ῌ-**)San Quintin: front+/**ῌ,3** (,/ῌ.2) ,** (1),** (1)+,** (.*)//* (+1) left; * right+.** (.1)+*** (--)
0** (,*) left; * right,**ῌ/** (+2ῌ./), andconsiderable thinning*no substantial change*, left; ,** (+2) right-** (,1)slight retreat?
+** (3) left; 2/* (,1) rightca. ,** (.*), andconsiderable thinning,** (.*),/* (/*)
max -/* (1*) right front.**ῌ++** (2*ῌ,,*)+.** (22) for 1/ῌ3++**ῌ,** (,*ῌ.*)+** (--)-1** (+,--), due tosnout disintegration,** (01)+** (--)
0* (,*), left (small part) a/* (ῌ+1), right (small part)no substantial change, but
considerable thinning
retreat?
+3* (0-) small partmax -** (+**) right front
ca. /* (+1)
ca. /* (+1) tip of snout
no data+/* (1/) partno substantial change

Gualas: N:S
San Rafael*
a .** (ῌ+-), butnarrowed by ,** (1)+** (-),/* (2).**ῌ3** (+-ῌ-*)

3** (-*)/** (+1),/* (,-)-** (,1)ca. .** (2*)
ca. -/* (1*)-/* (++1)+2* (0*)ca. ,** (+**)
ca. +/* (1/)

10* (,/)+*** (--)+-** (.-)
no substantial change/** (+1),*** (01)+** (3),/* (,-)
slight retreat
no substantial change+** (3) center
2/* (11)no substantial change
no substantial change.** (2*)
ca. -/* (1*)+/* (-*)
1* (+.).* (+-)
no substantial changeslight retreat
no substantial change,* (1) right front+/* (/*)

a -* (ῌ+/)
no substantial change/* (,/)
ca. 3** ./*)
no substantial change/* (,/) tip of snout*, but narrowedby .**ῌ1** (+-ῌ,-)-/* (-,), and narrowedby -**ῌ0** (,1ῌ//)ca. ,/* (2) center+** (-)-** (+*)+/*ῌ.** (/ῌ+-) apparent,partca. +/*? (/) right front/*ῌ+/* (/ῌ+.),** (+2)*
max ,** (+2) apparent,
right front
ca. +** (3)no substantial frontal change, a -** (ῌ+**), and snout isbut narrowed by ca. +** (,*) bending and breaking up
and snout is bending andbreaking up+**ῌ+/* (,*ῌ-*)+/* (/*) tip of snout+/*ῌ.** (,*ῌ2*)/* (+1) part,** (.*)no datano substantial frontal change, no substantial change?,
but considerable thinning
but thinning*?

: N side ca .** (1): S side ca. ,./* (.+)
Benito+3/* (--)
HPN+-+** (/,)
HPN,-*/* (/+)
HPN,3** (.2)
Southern Side
Ste#en: front-+** (/,): E side+/** (,/)
Eastern Side
Piscis+*/* (+2)
Pared Sur++/* (+3)
Pared Norte,*/* (-.)
Arco+-** (,,)
Colonia++/* (+3)
Cachet: N.2/* (2+):W-1/* (0-)
Nef-.** (/1)

Soler
Leon
Fiero
Exploradoresca. 2/* (+.)
ca. ,/* (.)+*/* (+2)
ca. //* (3)active front? ca. +.** (,-)

Glacier Period+330ῌ33+333ῌ,***

Period,***ῌ,**,

ca. +** (/*)
ca. 1* (-/) partno substantial change
no substantial change?, but
considerable thinningslight retreat?
ca. -** (+/) small part
0* (-*)
no substantial change
0* (+,) tip of snout for 3+ῌ30
no data,2** (+.**), due to snout
disintegrationno substantial change
no substantial change
ca. +2* (-0) for 3+ῌ30
no substantial change?,
but thinning?

,**,ῌ,**.

,**.ῌ,**/

Northern Side
Grosse+/* (/*)

no substantial change,
pitted poolno substantial change,
pitted pool enlarged

max. +.** (1**)

Western Side
Reicher: NE: SW/* (+1),/* (2-), right side*#-**# center#-**ῌ//* (+/*ῌ,1/)#

snout detached from blocking wall
max /* m, center partmax.+*** (/**)#

Gualas: N:S
San Rafael,2* (1-) (uncertain)
a -+* (ῌ+*-) parta -,* (ῌ+*1)+/*
1**
ca. +/*ῌ./*ca. //* (,1/)
a ca. ./* (ῌ,,/)max ./* (,,/) centermax +.** (1**)#*

a ca. +/* (ῌ1/) in the centerno substantial change

max ,-** (++/*)
protruding snout on rightno substantial change
no substantial change
ca. +** (/*)
max. ,** (+**)
max .** (,**)
a max +/* (ῌ1/)

max +,**San Quintin: front

no data for frontal change(probably no change but thinning): N side no data (probably slight retreat?): S side slight retreat
Benitono dataHPN+
no dataHPN,
no data
HPNno data
Southern Side
Ste#en: front
no substantial change: E sideno substantial change
Eastern Side
Piscis-* (+*) right side
Pared Surno substantial change
Pared Norte+** (--) left sideArcono substantial changeColonia+/* (/*)
Cachet: N
ca. .* (+-) debris-free part:W
Nef
0**ῌ+,** (,**ῌ.**)

Soler
Leon
Fiero
Exploradoresca.,** (01) R & L sides of snout
no substantial change/* (+1) tip of snout
ca. ,** (01) for 20ῌ33, andthinning
active front? ca. -** (+**) for 20ῌ33

ca. +*** (,/*) right side for 30ῌ**, max +*** (/**)
and considerable thinning*ca. -** (1/) for 30ῌ**
max /** (,/*)+**ῌ,/*
narrowed by +/*ῌ,/* (-2ῌ0-) for 30ῌ** ,** (+**)
ca. ,** (/*) for 30ῌ**
ca. +/* (1/) R & L fronts
ca. ,/* (0-) for 30ῌ**
ca. +** (/*)
ca. 1/* (2-) for 3+ῌ**
ca. ++/* (/1/)

no substantial change

no substantial change.**
ca. ,**, right half
ca. /*, left & right margins,/*
ca. +/*

ca. .** L side of snout ##ca. -/* (+1/) L side of snout max 3** (./*)
max ,** (+**) small part./* (,,/)-**
max ,**+**
no substantial change
no data*no substantial change+**

ca. +** (/*)
ca. ,** (+**) R side of snout/*ῌ+** (+1ῌ--) for 33ῌ*,*+/* (1/) L tip of snout
max -/* (+1/) centerca. +/*

no substantial change*
no substantial change**-/*, right edge*/*/*, left & right margins

ca. /*
no substantial change+/*
no substantial change

ca. +** (/3)
no substantial change+** (/*)*
max ,/* (+,/) middle partmax ./* (,,/) N branch##/*ῌ+** (,/ῌ/*) W branch##a ,** (ῌ+**)ca. /* (,/) R & L sides of front -** (+/*) tip of snout broke o#*+** (/*) parta ca. +** (ῌ/*) left half*
ca. +/* (1/)
ca. +** (/*)
ca. +**, left side
no substantial change
no substantial change
no substantial change
snout area becoming hummocky snout becoming hummocky
snout becoming hummocky
no substantial change
no substantial change+** (/*)?
*?
Source: Aniya (,**+) for +3./ῌ,***: however, for some glaciers, statistics were extensively modiﬁed with new vertical aerial photographs (+331/32) and satellite images.
* does not necessarily agree with the sum of each period, because the ﬂuctuated part may be di#erent for di#erent period.
# two fronts combined because of large recession.
a: advance## due to retreat joining branches were separated into two snouts

,.., (*.*2+)*..3 (*.*+0)+.., (*.*.1)*.31 (*.*-,)*?
*.31 (*.*-,),.02 (*.*23)+..0 (*.*.3)*..* (*.*+-)*.*, (*.****1)*.+/ (*.***/)*.2/ (*.*,2)*.+. (*.***/)

2..- (*.+.+)*.2, (*.*+.),.*. (*.*-.)+..0 (*.*,.)*..0 (*.**2),.*3 (*.*-/)/.+/ (*.*20)/.*- (*.*2.)+.1, (*.*,3)*.// (*.**3)*.3* (*.*+/)+... (*.*,.),.*3 (*.*-/),3.,1 (*.*.,)*.0+ (*.*,*)*.-0 (*.*+,)*.+- (*.***.)*.+1 (*.***0)-./0 (*.++3)
2.+2 (*.,1-)*.00 (*.*,,)+.1/ (*.*/2)+..+ (*.*.,)*.,, (*.***1)

2.2- (*.+.1)##..3+ (*.*2,)##+,.0. (*.,++),2.2/ (*..0.),./+ (*.*.,)..-3 (*.*1-)..*/ (*.*02)-.-2 (*.*/0)+*+.-0 (*.*2*)*.-3 (*.*+-)+3./ῌ1/,.1+ (*.*./)+3./ῌ,**/+,./2 (*.*/*)*.*, (*.**,)*.,1 (*.*,/)*.*. (*.**.)*?
*.*3 (*.**2)*.2- (*.*1/)+.+, (*.+*,)*.,. (*.*,,)*.+3 (*.*+1)**.+- (*.*+,)*.+. (*.*+-)*.-3 (*.*-/)+.-+ (*.++3)*.0. (*.*/2)*.+3 (*.*+1)*.-/ (*.*-,)..2- (*..-3)*.21 (*.*13)*.*1 (*.**0)*.-1 (*.*-.)*?
*..+ (*.*-1)*.,, (*.*,*)+31/ῌ20+-.2+(*.+-,)***.,1 (*.*/.)*.+0 (*.**-)**.,2 (*.*/0)*.+. (*.*,2)*.-+ (*.*0,)*.,* (*.*.*)*.-0 (*.*1,)*.+, (*.*,.)*?
*?

+.*0 (*.,+,)*.+/ (*.*-*)*.3. (*.+22)*.+. (*.*,2)*-.0* (*.1,*)..1. (*.3.2)*.+3 (*.*-2)+.,* (*.,.*)+.-, (*.*2-)**.++ (*.*,,)*+320ῌ3+0./3 (*.+*/)*.*+ (*.**-)***?
*.*0 (*.*,*)*.,* (*.*00)*.*2 (*.*,1)*.*2 (*.*,1)
a*.*- (῍*.*+*)
uncertain*?
?

*.1+ (*.,-1)*.++ (*.*-1),.,+ (*.1-1)*.+1 (*.*/0)*.+- (*.*.-)*.***0,.-0 (*.121)*.+, (*.*.*)*.++ (*.*-1)*.*, (*.**1)
no data*.,/ (*.*2-)+33+ῌ3.

-..2 (*.*3,)

a*.*+ (῍*.**/)**.*. (*.*,*)*.,/ (*.*/*)***.*, (*.*+*)+.,+ (*.0*/)***.+, (*.*,.)**?
?

*.-2 (*.+3*)*.+. (*.*1*)*?
*.,/ (*.+,/)##*.*+ (*.**1)*.2, (*..+*)*.,2 (*.+.*)*.*, (*.*+*)*.*. (*.*,*)no data*.,2 (*.+.*)+33.ῌ30

Period/.+. (*.*3/)*.*+ (*.**-)**.*0 (*.*,*)**.+/ (*.*/*)*.-- (*.++*)*.11 (*.,/1)*.,+ (*.*1*)**.*, (*.**1)*.-1 (*.*,2)*+.-3 (*.+*1)**./1 (*.+3*)*.*0 (*.*,*)*.+0 (*.*/-)*.-+ (*.+*-)
a*.*1 (῍*.*,-)
a*.20 (῍*.,21)-.,- (+.*11)
no datano datano datano data*.+3 (*.*0-)+330ῌ33/.*, (*.,13)*.*0*?
no data
*
*
*.+
*.+/
*.*/
*
*.+0
*
*

*./2

*.,+
*.,*
*.*0
*..*
*.02
,.,+
*.,/ (*.*0-)**.,* (*.*/*)**.-+ (*.*12)*+.*/ (*.++1)**.+0+333ῌ,***

1.1. (*.+10)*.++ (*.*//)*.+0 (*.*2*)*.*0 (*.*,*)***.*. (*.*,*)*.,- (*.++/)*.*- (*.*+/)*.*/(*.*,/)*.*0 (*.*-*)*.+2 (*.*3*)***.2+ (*..*/)*.13 (*.-3/)##*.-0 (*.+2*)
a*.,0 (῍*.+-*)*.-3 (*.+3/)-.-- (+.00/)*.,+ (*.+*/)*.,* (*.*+*)*.+. (*.*1*)+.** (*./**)*.++ (*.*//),***ῌ,**,

0.** (*.+-0)*.*, (*.*+*)**.*, (*.*+*)**.+* (*.*/*)*.,0 (*.+-)
a*.+0 (*.*2*)*.-/ (*.+1/)
a*.*/ (*.*,/)*.*1 (*.*-/)**.,, (*.++*)?

*../ (*.,,/)*.01 (*.--/)##,.** (+.**)##
a*.*1 (*.*-/)*.2+ (*..*/)*.,3 (*.+./)*.*3 (*.*./)*.-/ (*.+1/)
a*.*/ (*.*,/)*.0- (*.-+/),**,ῌ,**.

Glacier Variation of the Northern Patagonia Iceﬁeld, +3.././ῌ,**./*/ (area lost in km, with the mean annual rate/glacier).

..+3 (*.,**)

*
*
*
*
*..*
*.*+
*.*0
*
*
*.*2
*
*

*.0.

ῌ*
,.-*
*.*2
ῌ*
*...
*.+.

*

*.*.

*

,**.ῌ,**/

Source: Aniya (,**+) for +3./ῌ,***; however, for some glaciers, statistics are extensively modiﬁed with new vertical aerial photographs (+331/32) and satellite images(,***, ,**-).
#: combined (NE and SW for Reicher: N and S for Gualas).
##: Total, excluding Exploradores (real?). Also excludes data covering more than one period: therefore the grand total does not agree with the sum of the total of each period.
The total (+3./ῌ,**/) of each glacier does not necessarily agree with the sum of each period, because lateral retreat was included in +3./ῌ*/.
*: includes (a) preceeding period(s) with * ?, no data or uncertain.
a: advance.

Total##

Northern Side
GrosseWestern Side
Reicher: NE: SW
Gualas: N:S
San Rafael
San Quintin
Benito
HPN+
HPN,
HPNSouthern Side
Ste#enEastern Side
PiscisPared Sur
Pared Norte
Arco
Colonia
Cachet
Nef
Soler
Leon
Fiero
Exploradores
real?

GlacierTable ,.

62
Bulletin of Glaciological Research

63

Aniya

Fig. ,. HPN Glacier variations for +3.././ῌ,**./*/. Glaciers are listed
counterclockwise from the north and the spacing between names isarbitrary. One tick on the right ordinate indicates + km, of change
in area (downward, loss; upward, gain).

bably caused by crevasse stretching.
Glaciar San Quintin, the largest glacier of the
HPN, lost an area ca. ,3 km,, which is by far the largest
loss, while Glaciar Reicher SW made the longest retreat in a proglacial lake, about 0*** m in 0* years.
The second longest retreat, close to /*** m, was foundat Glaciar Cachet, causing its snout to split into two,and only the west terminus barely remains in the
proglacial lake now. HPN+, which is one of the few
land-terminating glaciers, varied a little during the+33*s when many other glaciers made a rapid retreat.
Calving glaciers
As of ,**/, +1 of the ,+ monitored outlet glaciers
were calving glaciers. It was found out from the+331/32 aerial photographs, Landsat ETMῌ images
from ,***, ,**+ and ,**-, and the aerial surveys by
Aniya that the amount of calving and the size of
icebergs ﬂoating in the proglacial lake are distinctively di#erent among those calving glaciers, particularly during the +33*s and the ,***s. Based on theiceberg characteristics at around ,***, calving glaciers
are categorized into three groups (Fig. -): (+) thoseglaciers that produce a lot of large (say, longer than+** m in length), tabular iceberg; (,) those glacierssuch as San Rafael that produce many, but normally..+small icebergs; and (-) those that produce no or very
little icebergs. Since the stage (,) or (-) can be recognized before and/or after the stage (+) at some glaciers,
these characteristics appear to indicate the stage in
the glacier retreat at some glaciers.
Glaciers producing large tabular icebergs and/or
went through recent snout disintegration
Snout disintegration in the proglacial lake appears to be characteristic for those of the HPN calving
glaciers that produce a lot of large tabular icebergs,
particularly since the +33*s. These events are characterized by many large icebergs that are densely packed in the lake. The ﬁrst such event was recognized
at Glaciar Reicher around +33+ῌ+33. at the SW terminus, retreating -1** m and losing ,.,+ km,. Since
then, this glacier had produced large icebergs, sometimes exceeding /** m in length, before the terminus
has recessed into the conﬁned valley. Then it occurred at Glaciar Nef around +33.ῌ30, retreating ,2**m and losing +.+, km,. At Glaciar Ste#en, terminus
retreated a maximum of 3** m in two years (,**,ῌ
,**.), losing an area of *../ km,. In terms of the area
loss, Ste#en has been losing a large area since the mid+32*s. HPN- made small snout disintegration around,***ῌ,**,, retreating ++/* m and losing an area of
..+.+

64

Bulletin of Glaciological Research

Fig. -. Classiﬁcation of calving glaciers of HPN, as of around ,***.
(./) indicates the year when calving was recognized with remote sensing data. In this case, +3./.
῍Glaciers whose snout is (was) (near) ﬂotation: Reicher SW, Gualas N&S, San Quintin N & W, HPN-, Ste#en, Nef, San
Quintin S? Some characteristics of these glaciers (near ﬂotation); (+) producing a lot of large tabular icebergs; (,)
irregular terminus ﬂuctuation (such as part advance while other part retreated)-Reicher SW, Gualas N&S, Ste#en; (-)
apparent advance before extensive calving-San Quintin W, Gualas N & S, Reicher SW?, Nef?; and (.) snout bending in
proglacial lake- Nef, Reicher SW.
῍Common characteristics of those glaciers producing few icebergs: slow, steady little retreat.
῍Since ,***, Glaciar Cachet moved to category ‘Few Icebergs produced’, Glaciar Benito moved to ‘Large Icebergs’, andGlaciar Reicher SW was combined with NE to become Reicher in ‘Small Icebergs’ category.

+ km,. However, it made a small advance in ,**,ῌ
,**., extending about +/* m with an area increase of*.*/ km,.
The largest glacier of the HPN, Glaciar San Quintin
has lost by far the largest area ca. ,3 km,; however,the +331 vertical aerial photographs taken by the
Chilean Servício Aerofotogramétrico (SAF) shows avery interesting feature of splaying crevasses near thewest front (Fig. .). A zigzag pattern was formed (Fig.
.A), which can be interpreted as the result of being
pushed from behind against the terminal moraine,suggesting that the glacier advanced. The Landsat
ETMῌ of March ++, ,**+ (Fig. .B), reveals that thispart had retreated since, leaving open water between
the moraine and the glacier front. This variationsuggests that the advance revealed in the +331 photograph was just ephemeral rather than a robust ad
vance, which was probably caused by crevasse stretching, thereby the glacier became thinner with crisscrossed crevasses, facilitating easy breaking up of theterminus. The same phenomena occurred before
here. Winchester and Harrison (+330) reported an advance in +33. from ﬁeldwork, which, however, Aniya
and Wakao (+331) interpreted as an ephemeral advance probably caused by crevasse stretching, fromthe interpretation of the oblique aerial photographs
taken before and after +33.. This interpretation was
subsequently proved correct (Aniya, ,**+). Retreat
has been accelerated during the +33*s and the ,***sand large-scale snout disintegration appears to be imminent (Fig. .C & D).
The similar phenomenon was detected at thenorth terminus of Glaciar Gualas in +33.. Again, Harrisonand Winchester (+332) reported an advance in +33. inthe ﬁeld. Aniya and Wakao (+331) also reported anadvance from the aerial surveys of +33- and +33/;
however, they suspected this was just an ephemeral
advance due to crevasse stretching, which was conﬁrmed by the subsequent retreat (Aniya, ,**+). The
advance of the Gualas’ south terminus between ,***ῌ,**, also appears to have been caused by crevasse
stretching. The manual interpretation of the Landsat ETMῌ of March 2, ,*** suggests that what appeared to be the advanced part could be a tight packof icebergs, which was the result of the terminus
disintegration. Subsequently, Glaciar Gualas’ termi
nus disintegrated around ,**,, although densely packed icebergs remained cramming the lake until ,**/or so. Before the onset of the large-scale disintegration, small advances were observed at the south terminus for +330ῌ+333 and ,***ῌ,**,. Glaciar Gualas also
had two calving fronts in a round-shaped proglaciallake, but due to disintegration of terminus in ,**,ῌ
,**., the snout became one and recessed into thevalley now.
At Glaciar Reicher that retreated most, an interesting phenomenon was captured by a series of aerial
surveys and satellite images from +333 to ,**.. Figure / shows a sequence of a huge iceberg calving,glacier retreat/advance/retreat and drifting of thaticeberg. In Figures /A (Nov. +333) & B (March ,***),
the snout was more or less still intact, although splitting was recognized on the right. In Figure /C(March ,**+) the snout had split into three sections
with advance of the left section, producing a mediumsized iceberg (close to -** m across). Six months later

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Aniya

Fig. .. Rapid recession of Glaciar San Quintin. A: Vertical aerial photograph (February +3, +331, by SAF, Chile). B:
Landsat ETMῌ (March ++, ,**+). C: Landsat ETMῌ (April ,, ,**-). D: Oblique aerial photograph (August +/, ,**/,
by Aniya). For easy comparison with oblique aerial photographs, satellite images were rotated 3* degrees
counterclockwise so that the north is to the left.

(Fig. /D), the left section of the snout broke o#, becoming a huge iceberg (about ++** m῍-1* m, *.-, km,).
On this image, darkened glacier surface in the snout
area is very conspicuous, which is also weakly recognizable in Figure /C. Four months later in Figure /E,
the central part of the snout had collapsed, and surprisingly the huge iceberg drifted back to near thesnout. Darkened glacier surface is clearly recognizable in this image. Three months later in Figure /F(Feb. ,**,), the right section had advanced and thewhole snout area became very dark. In Figure /G(April ,**-), +. months later, the proglacial lake waschoked with icebergs and the huge iceberg drifted
down a little toward the southwest (SW) outlet, whichsurprisingly maintained the size (about 3** ῍-** m)even after +./ years since calving. In Figure /H (Dec.
,**-), the iceberg drifted back about ,.- km to the fjord
entrance. In this image, the dark glacier surface ofthe snout area has almost gone with a vestige at theleft front. Seven months later in Figure /I (July,**.), interestingly the iceberg had been pulled into
fjord and rotated clockwise about +/*῎, indicating
very complicated lake current near the snout. Fig-

ures / J & K (Dec. ,**.) show that the iceberg drifted
down sideways since, and in Figure /K, two large
icebergs can be seen, of which the one on the upstream side seems a newly calved one.
From this sequence, several interesting features
about calving at Glaciar Reicher (or other Patagonian
calving glaciers) can be pointed out: (+) the terminus
was ﬂoating before large calving; (,) glacier made anapparent advance before calving; (-) the huge iceberg
remained more or less intact for a long time (nearlyfour years).
Glaciar Reicher used to have two terminuses, NE
and SW, which terminated in respective proglaciallake that has own outlet stream at the damming terminal moraine. Due to rapid recession during theearly +33*s, the two terminuses had become almost asingle one as can be seen in Figure /A. After large
calving evens described above, the glacier further
retreated and the two proglacial lakes coalesced. So
the two outlet streams located at the both end of the
proglacial lake play a trick on current with strong
winds, thereby having caused drifting back and forthof the huge iceberg. In addition, near the terminus,

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Fig. /. A sequence of a large calving event at Glaciar Reicher and glacier variations between +333 and ,**.. See text for
detailed description of events. A (Oblique by Aniya, Nov. -*, +333); B (Landsat ETMῌ, March 2, ,***); C (Landsat
ETMῌ, March ++, ,**+); D (ASTER, Sept. -, ,**+); E (Oblique by Aniya, Nov. ,3, ,**+); F (ASTER, Feb. +*, ,**,); G(Landsat ETMῌ, April ,, ,**-); H (Oblique by Aniya, Dec. +2, ,**-); I (Oblique by Aniya, July ,/, ,**.); J & K Obliqueby Aniya, (Dec. ,/, ,**.). For easy comparison with oblique aerial photographs, satellite images were rotated 3*
degrees counterclockwise so that the north is to the left.

water discharge from the glacier counteracts with thelake currents, thereby producing very complicatedcurrent patters that caused rotation of the iceberg.
Whether or not the ephemeral dark glacier surface in the snout area between ,**+ and ,**- wasassociated with this large calving and the subsequentglacier variation pattern cannot be assessed. The
sudden appearance and disappearance of such surface
is mysterious, because large dark area in the surfaceof the ablation part in Patagonia is normally coatedwith volcanic ash or covered with landslide deposits;
however, in this case it does not appear either.

The sequence of this very interesting events thatwere accidentally captured by a series of remote sensing data strongly indicate the need of close monitoring of Patagonian calving glaciers that dynamicallychange in a short period of time.
Glaciers producing many small icebergs
Glaciar San Rafael, the second largest glacier ofthe HPN, has been producing a lot of small icebergs
during the +32*s and +33*s (Warren et al., +33/). The
section ..+.. discusses about this glacier in detail.
Glaciar Cachet used to produce a lot of small
..+.,

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Aniya

icebergs during the +33*s when it was retreating very
actively; however, due to large retreat, the snout has
now totally separated into two, and only the west
terminus terminates in the lake with no icebergs.
The north terminus is totally detached from the lake
by now. The glacier retreated fairly rapidly during
the periods of +3./ῌ1/ and +31/ῌ20, compared with theother glaciers of the HPN (Tables + & ,). For theperiod of +3./ῌ1/, the retreat was about ,*** m with anannual mean rate of 01 m, and for the period of +31/ῌ
20, it was 2/* m with an annual mean rate of 11 m.
The situation at Glaciar Reicher NE appears thesame as that at Glaciar Cachet. Until around ,**+
(before the snout became one) Glaciar Reicher NE
produced only small icebergs with slow retreat; however, it retreated ,-/* m between +31/ and +320, withan annual mean rate of ,+. m. The other terminus of
the glacier, Reicher SW disintegrated between +33+
and +33., retreating -1** m (an annual mean rate of+,-- m).
Due to the coarse monitoring interval, we cannot
ascertain whether these very rapid retreats of Cachet
and Reicher were at a fairly constant, steady rate overthe period, or were e#ected in a short period of timewith the disintegration of terminus at (near) ﬂotation.
The snout disintegration at Glaciar Nef was accidentally caught by radar images (Wada and Aniya, +33/),
showing that it occurred in a short period of time (lessthan ﬁve months). Ground observation at Glaciar
Upsala of the HPS tells that snout disintegration occurred in a day or two (Aniya and Skvarca, +33,;
Naruse et al., +331; Skvarca, personal communicationin +33+). These records strongly suggest that thelarge retreat at Cachet and Reicher NE occurred in ashort period of time with the snout disintegration
rather than at a constant, steady rate over the period.
Glaciar Benito started calving only sometime between +320 and +33+ due to constant recession since+3./. Presently, it actively produces a fairly large
number of medium-sized icebergs and its terminus
appears grounded at the moment, with steep surface
gradient.
Glaciers with no or few icebergs
Glaciar León, located on the northeast side of the
HPN, varied very little since +3./, with the second
smallest retreat (*.// km,). Within a trend of the general retreat, it even made a small advance, twice in+33+ῌ3. and ,**,ῌ,**.. It consists of three bodies,
León North, León Central and León South, and it isremarkable that none of them has made a substantial
retreat over the last 0* years. Glaciar Fiero, locatedjust north of Glaciar León, had been almost stagnant
for a long time +3./ῌ+33+; however, it started slow
retreat after +33+ and the retreat has became steady,although slow after +333.
Glaciar Colonia has been slowly retreating from..+.-

+3./ to ,**., but it lost a relatively large area (*.. km,)in ,**.ῌ,**/. This was caused by the land-based part(right half; the left half is in a proglacial lake) and it
appears that the continued thinning ﬁnally took an
e#ect on retreat. Consequently, the terminus now
has become totally surrounded by water, although it
appears shallow. During the early +33*s, thrustingnear the terminus was very active (Wada and Aniya,+33/), but now it seems no longer thrusting.
Glaciar Pared Norte retreated very little, although
the upper glacier area around the bend has sharply
decreased. Glaciar Piscis has varied very little, thethird smallest variation during the last 0* years and it
even made a small advance during +33.ῌ30. Glaciar
Soler formed a proglacial lake during the +33*s on theeither side of the terminus, and with the continuing
steady retreat, the proglacial lake has become encircling the terminus completely by ,***. HPN, hadbeen retreating slowly, but made a large area loss
between ,**. and ,**/. The terminus now appears
ﬂoating or near ﬂotation, with a pocket of open waterin the snout area, indicating a large breakdown in thenear future.
Contrasting behaviors of Glaciares San Rafael
and San Quintin
The contrast in behaviors of the neighboring glaciers, San Rafael and San Quintin, is very interesting.
Glaciar San Quintin has lost the largest area (,2.2/km,) since +3./ with by far the fastest rate (see Fig. ,).
After a slight slack in the retreating rate between +31/
and +320, the rate has picked up, producing a lot of
icebergs in the proglacial lake.
On the other hand, Glaciar San Rafael, the only
tidewater glacier in the HPN, has a unique history of
the variation. It retreated very rapidly between +31/
and +33+; however, it become still-stand for +33+ῌ30
and made small advances during +330ῌ33 and ,**,ῌ*.,which made the variation contrasts after +33+ very
distinctive (Fig. ,). Between +31/ and 20, it retreated,,** m at an annual mean rate of ,** m, and between+320 and +33+, a maximum of +/** m at an annual
mean rate of -** m, which were by far the largest ratein the whole Patagonia. Between +333 and ,***, it
retreated a maximum of ./* m, and for ,***ῌ,**,, amaximum of ./* m (,,/ m/a), at di#erent front sections though. These retreating rates are comparable
to those of +31/ῌ20 and +320ῌ3+. Based on these fast
retreating rates, Venteris (+333) implied that the terminus of Glaciar San Rafael then was at near ﬂotation.
If so, the still-stand and advance during the +33+ῌ33
can be explained by topographic control, as Aniya(,**+) pointed out, rather than the precipitation increase at Cabo Raper (Warren, +33-; Winchester andHarrison, +330; Aniya and Sato, +330). Around +33+,
the retreat stopped where the width of the fjord narrows. While still-standing there, the glacier regained
..+..

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Bulletin of Glaciological Research

thickness and started advance around +330. Due toadvance into the wider area, the snout spread out
thereby getting thinner, which in turn made the snout
condition near ﬂotation.
They both are located on the western side of theiceﬁeld, next to each other north (San Rafael)ῌsouth(San Quintin), and their accumulation areas with the
obscure divide between them lie on the windward of
the westerlies. Glaciar San Rafael terminates in afjord now, while Glaciar San Quintin terminates in alarge, fresh-water proglacial lake. Since there seems
no di#erence in the condition of the accumulation
areas of the two glaciers, fjord topography (chieﬂywidth) appears to have strongly inﬂuenced the variation of Glaciar San Rafael since the +33*s.
..+./ “Height-above-buoyancy” model
Van der Veen (+330) proposed a model called “heightabove-buoyancy” to explain a rapid retreat of calving tidewater glacier, in which the position of thecalving front is controlled by the local water depth
such that, at the terminus, the ice thickness in excess
of ﬂotation cannot become less than a certain threshold value (῍/* m for Columbia Glacier (Van der Veen,+331, p. +0.ῌ+0/; ,**,). This model may explain somePatagonian calving glaciers that underwent a rapid
retreat during the +32*s and the +33*s.
However, the bathymetry is not available formost glaciers in Patagonia. Glaciar San Rafael is oneof the few exceptions, where the bathymetry is available (Nakajima et al., +321; Warren, +33-). According
to them, the water depth of the fjord center part
ranges from about +2* m to over -** m, while thedepth of the Laguna section is less than ,** m. Naruse(+32/) measured the height of the calving cli# (seracs)
to be /*ῌ1* m at Glaciar San Rafael in November +32-.
If we compare the terminus position in +32- (Aniya
and Enomoto, +320) and the bathymetry (Warren,+33-), the water depth near the terminus is about +-*ῌ
+2* m. Assuming that the glacier was grounded in+32-, and if we apply the “height-above-buoyancy”,
expressed as h῏drw/ri, where h is ice thickness (+2*῎
0*ῐ,.*), d water depth, rw water density, and ri ice
density (3** kg m῏+), the “height-above-buoyancy” isabout .* m. Since the terminus is very jagged because of many seracs due to heavy crevassing, many
parts could have been at near-ﬂotation even in +32-.
Near the +33, terminus position, the average depth of
the fjord is about +.* m with a maximum of over -**m near the center (Warren, +33-). With this depth thecenter part of the glacier could have been ﬂoating.
The width of the fjord narrows near the +33, terminus
position.
The “height-above-buoyancy” model, in conjunction with change in the fjord width, may explain the
rapid retreat during the +32*s and the subsequent
still-stand and advance during the +33*s. The fjord

Fig. 0.
Glaciar Grosse: completely debris-covered
glacier with a recent retreat, forming a proglaciallake. A: Vertical aerial photograph (December 3,+31., by Chilean IGM). B: Vertical aerial photograph (March ++, +331, by SAF, Chile). C: Oblique
aerial photograph (August +/, ,**/, by Aniya). In
A and B, the north is down to facilitate an easiercomparison with C.

width a#ects the glacier thickness and the heightabove-buoyancy as follows. When the glacier terminus advances into the wider area of fjord, the snout
area spreads out, thereby getting thinner, and theheight-above-buoyancy decreases. Conversely, when
the glacier recedes into the narrower part, glacier gets
thicker, and the height-above-buoyancy increases.
In addition, fjord depth plays a role. When the glacierterminus retreats further into fjord with increasingwater depth, the height-above-buoyancy decreases,
causing the terminus to ﬂoat. Then calving becomes
more active and the glacier rapidly recedes until theterminus reaches where the fjord becomes su$ciently
narrow and the glacier becomes thick enough to maintain the height-above-buoyancy. When the glacierattains enough thickness while stagnant, it starts advancing into the wider area, where the glacier getsthinner causing more calving and consequent retreat.
Debris-covered glaciers
There are ﬁve glaciers whose snouts are heavily
covered with debris, Glaciares Grosse and Exploradores on the north side of Monte San Valentin (-3+*m), Glaciar Fiero on the east side of Monte San Valentin,
and Glaciares Pared Sur and Arco on the southeast
side of the iceﬁeld. Except for Glaciar Grosse, theterminuses of all debris-covered glaciers are land..,

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Aniya

based.
Particularly Glaciar Grosse is completely covered
with debris so that there is no white part visible.
Because of thick debris-cover, the retreat of Glaciar
Grosse was slow until +33+. A proglacial lake started
to appear around +320, and after +33+, the terminus in
the proglacial lake become pitted topography withmany supraglacial ponds (Fig. 0). Subsequently
these ponds had coalesced to become larger ponds,
which were eventually connected with the steadily
growing proglacial lake. In contrast to this behavior,
the neighboring Glaciar Exploradores has remained
more or less the same since +31/, with a small retreat
between +330 and +333 (Table + and Fig. 1). Althoughdebris has accumulated in the terminus area, the glacier is still actively moving (Aoki and Sawagaki, ,**0),and the position of the terminus has remained more orless the same. However, from the ﬁeld observation
during the ,***s, the glacier was found to have beenslowly melting. The di#erence in these behaviors
could be attributed to the winter precipitation patterndeduced from Landsat winter images (e.g., July +,,+333; July ,/, ,**- among others) when those glacierson the east side (i.e., Exploradores) receive more snowfall than those on the west side (i.e., Grosse). Glaciar
Fiero had varied very little for +3./ῌ+333; then it commenced a slow, but steady retreat.
Glaciar Pared Sur located on the east side of Co.
Pared Sur (ῌ-*** m) varied very little since +31/,

which can probably be attributed to thick debris
cover that insulated the underlain ice. Glaciar Arco,
coming from the eastern side of Co. Arco (ῌ-*** m)showed the smallest variation among the ,+ outlet
glaciers of the HPN, probably due to thick debris
cover on the terminus area.
Cause for variations
The detailed discussion about the relationshipbetween climate data and the glacier variation wasprovided in Aniya and Wakao (+331) as well as Aniya(,**+). The most common factor for the general recession of the HPN glaciers over the last 0* years is
climatic, i.e., temperature rising and/or precipitation
decrease.
In addition, at some calving glaciers, there is a
topographic control. At Glaciar San Rafael, for example, because the width of the fjord changes whererecent frequent variations of stagnation/advance/retreat have occurred, the fjord topography seems playing an important role in the variations now.
..-/.

Conclusions

Variations of ,+ outlet glaciers over the last 0*
years of the HPN indicate that glaciers have been in
the trend of general retreat, at some glaciers verystrong while at others rather weak. The trend of theretreat has become stronger after the +33*s. Seventeen glaciers out of ,+ are now calving, more or lessand six of them became a calving glacier due to theretreat over the last 0* years. The frontal area lost
due to recession amounted to ca. +** km, in 0* years,
close to a third of which was e#ected at Glaciar San
Quintin, the largest glacier of the HPN. The neighboring tidewater glacier, San Rafael retreated at asimilar rate with San Quintin until ca. +33*; however,during the +33*s and the ,***s, its terminus position
had remained more or less the same with a cycle ofstagnation/advance/retreat, This contrasting behavior of Glaciar San Rafael and Glaciar San Quintin
during the +33*s and the ,***s may be explained by
the topographic control exerted by the fjord widthwith some inﬂuence of depth as well at Glaciar San
Rafael.

Acknowledgments

Fig. 1. Glaciar Exploradores: heavily debris-covered
glacier, with a little retreat, in contrast to Glaciar
Grosse. A: +31. vertical aerial photograph (December 3, by Chilean IGM) and B: +331 vertical aerial
photograph (March ++, by SAF, Chile). C: Oblique
aerial photograph (August +/, ,**/, by Aniya). In
A and B, the north is down to facilitate an easiercomparison with C.

This study was supported by a grant in aid for
Scientiﬁc Research of Japan Society for Promotion of
Research (No.+/,/-**+, Principal investigator, M.
Aniya). Aerial surveys were carried out by pilots,
Carlos Roberto León and Hugo Rosas of Transportes
Aereos “Don Carlos LTDA” of Coyhaique, Chile.
Their skilful ﬂights in the treacherous winds of Patagonia enabled me to take photographs. Comments,
particularly on calving glaciers made by Dr. Renji

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Bulletin of Glaciological Research

Naruse (NPO, Glacier and Cryospheric Environment
Research Laboratory, Tottori, Japan) are much appreciated.

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