|
.
That fall 2004 I posted my web page for the world to see. A number
of persons saw my pages and sent me email. I have corresponded with a
number of these persons and I have learned in the
process. I call these ice ribbons and ice flowers based on their
appearance. But the term frost flowers is commonly used while there
is the occasional use of ice fringes, ice filaments, and rabbit
ice.
I also employed bibliographic search tools to find out about frost
flowers. I found a few popular articles describing these unusual
items but could find no authoritative papers explaining these ice
formations. I found two plant species associated with the name frost
flower: Dittany, or Wild Oregano, Cunila
origanoides, and White Crownbeard,
or Frostweed, Verbesina virginica. Thus, I concluded this was
a concern for botany. I showed what I had found to many colleagues in
the biological sciences and only one had personally seen these frost
flowers and he thought they occurred on only Cunila
origanoides. He said he was sorry he
never took this on as a research topic.
Ice Flowers and Needle Ice
One person in Alabama sent
photos, three showing ice flowers and one showing needle ice. He suggested
they were related, but I rejected that association because I was convinced
it was a botanical issue. Then in Virginia in 2005 I found ice flowers and
needle ice in the same immediate area, as shown above. By golly, he
was right.
I went back to other correspondence and found another statement relating
ice flowers and needle ice. I then turned to bibliographic search
tools and found there is a well-developed professional literature on needle
ice. In 1988 D. W. Lawler published “A Bibliography of Needle Ice” in
Cold Regions Science and Technology (15: 295-310). There are
267 items in his compilation going back to 1824. I delved into many
of the papers cited there.
Stories from the 19th Century
Of particular note was the letter of J. F. W. Herschel dated January 12,
1833, in Philosophical Magazine, 3rd series, 110-111, entitled:
"Notice of a remarkable Deposition of Ice around the decaying Stems of
Vegetables during Frost." He wrote that years before he had
found ice ". . . to incrust the stalks in a singular manner in
voluminous friable masses, which looked as if they had been squeezed, while
soft, through cracks in the stems." Then on January 11 he found
a similar formation of ice which he described as ". . . seemed to
emanate in a kind of riband- or frill-shaped wavy excrescence, -- as if
protruded in a soft state from the interior of the stem, from longitudinal
fissures in its sides, . . . the structure of the ribands was fibrous, like
that of the fibrous variety of gypsum, presenting a glossy silky
surface" He goes on to make additional observations about the
ice and the atmospheric conditions when these formed, all consistent with
what I have observed more than a century and a half later. He ends
with "What share the physiological functions of the plant may have in
the phaenomenon, or whether it be connected with
the vitality of the stem at all, it is for botanists to decide."
Herschel’s paper prompted Professor Rigaud of Oxford to recall his observation in 1821
of similar ice formations on a recently built stone wall. “The
portions of the ice (with a single exception) were formed at the edges of
the stones -- indifferently at the tops, to bottoms, or the sides, but the
curvature was uniformly turned inward from the mortar itself, in which case
the threads of ice were formed in a horizontal line, and I think (for of
this I made no memorandum) parallel to the layer of the mortar.” Philosophical
Magazine, Feb. 2, 1833, 190-191.
In the same journal (The London, Edinburgh
and Dublin Philosophical Magazine and
Journal of Science, Third Series) of May 1850, 329-342, John LeConte, M.D., of the University
of Georgia wrote about many
instances of observing frost flowers and needle ice in Georgia.
He quotes liberally from Hershel (1833), for he appreciated the words as I
do. LeConte also produced some lovely
descriptions such as ". . . the traveler who passes along the level
roads of this region soon after sunrise cannot fail to be struck with the
remarkable accumulations of voluminous friable masses of semi-pellucid ice
around the footstalks of the Pluchea which grow
along the road-side ditches. At a distance they present an appearance
resembling locks of cotton-wool, varying from four to five inches in
diameter, placed around the roots of plants; and when numerous the effect
is striking and beautiful." p. 330. He observes that in some
cases ice had formed on the same plant on consecutive nights "when the
wood was not rifted." p. 332. He also makes observations about
what we now call needle ice and argues "that both of the phaenomena must be referred to the same cause.
If we admit an identity of cause in the two cases, it is obvious that it
must be purely physical . . ." p. 336.
In 1880, the Duke of Argyll writing in the January 22 issue of Nature
described such ice formations and asked for a scientific explanation of
this phenomenon. In the January 29 issue three persons weighed in
with opinions based on what they had seen. In the February 19 issue
the Duke responded. In the February 26 issue one of the earlier
writers and a new writer offer their suggestions based on ice formations
they have seen. All of these contributors were from what we now call Great Britain.
In the April 22 issue Wm. LeRoy Broun from Vanderbilt
University describes the growth of
needle ice and compares it to the ice formations observed in Europe. Broun does not reference LeConte who was also from the southeastern U.S.
A report on the meeting of the Physical Society in Berlin, in the March
13, 1884, issue of Nature includes a discussion from Prof. Schwalbe on
flowers growing from rotten twigs lying on the ground as ". . .
ice-excrescences of soft, brilliant, asbestine appearance, and uncommonly
delicate to the touch. . . ." Prof. Schwalbe brought some of
these withered and rotten twigs with him to Berlin, and it was in his power to
produce on them at any time the phenomenon just described. For this
purpose all that was needed was thoroughly to moisten the twig, in such a
manner, however, that no water dropped off, and then to let it cool slowly
in a cold preparation. Ice-excrescences also appeared of themselves
on twigs lying in the garden whenever the temperature fell below 0 degree
C. in the night." (p. 472) He made reference to the explanations
of LeConte, 1850. I originally assumed
these were ice flowers but subsequently I find others reporting this
phenomena on rotten twigs. I have a separate web page on these ice formations,
which are called Haareis, Kammeis,
Pipkrakes and Silk Frost.
In a later editions of Nature there were a series of letters
reporting on ice formations and reacting to earlier letters. Most of
these reports relate to what was obviously needle ice but in the January 1,
1885 issue B. Woodd Smith tells of a friend who
“. . . picked up a piece of a dead beech-branch which was covered
with filamentous ice, such as is described by the Duke of Argyll and
others.” This person found the ice reappeared again the next morning
when it was left out over night. (p.
194).
I marvel at the observations and vocabulary of these authors, writing
more than 120 years ago. Do we know more about frost flowers and needle ice
than they did back then? We certainly know more about needle ice, as
evidenced by the many articles cited in Lawler's bibliography. Among
these papers are reports of scientists growing needle ice and controlling
the rate of growth.
Lester F. Ward, “Frost freaks of the dittany,” The Botanical Gazette,
1893, observed these near Accotink, VA.
He has stylized drawings of the stems and ice ribbons. He writes that
the article belongs in a botanical journal because of all of the plants in
the area the ice formations occurred only on Cunila
Mariana, dittany. He and a colleague tasted the ice and inferred
from this that the water was not “. . . distinguishable from pure distilled
water . . .” p. 185 Ward said he was able to find no records of
others observing this phenomenon. He also wrote: “It is possible that
this is the first time that Cunila
Mariana has been discovered to be a frost-weed. At the time the
discovery was made it had quite escaped my memory that Helianthemum
Canadense behaves in a similar way.” P. 185.
Ward references Gray’s Manual, 1848, as describing such ice
formations on Helianthemum Canadense, or frostweed. As similar
statement appears in the Eighth Edition of Gray’s Manual of Botany,
1970, on p. 1017 and notes that Helianthemum Bicknellii
is also called frostweed.
Ward also refers to the book Sharp Eyes by Wm. Hamilton Gibson,
dated 1892. I got to see the 1904 edition of this delightfully
illustrated work, where Gibson writes about what can be seen in nature
every week during the year. The November 3d entry is The Frost-Flower
as it appears on Helianthemum Canadense. He notes it has three
distinct types of blossoms during the year. In November “the flower
from which the plant is named, but which few people ever see. Almost
any morning during the past week, after a severe frost, would have shown it
to us among the stubble where the plants are known to grow, glistening like
specks of white quartz down among the blown herbage close to the base of
the stem. It is a flower of ice crystal of purest white which shoots
from the stem, bursting the bark asunder, and fashioned into all sorts of
whimsical feathery curls and flanges and ridges. It is often quite
small, but sometimes attains three inches in height and an inch or more in
width. It is said to be a crystallization of the sap of the plant,
but the size of the crystal is often out of all proportion to the possible
amount of sap within the stem, and suggests the possibility that the stem
may draw extra moisture from the soil for this special occasion. The
frost-flower is well named.” The sketch accompanying this text shows
an blossom of ice in one image overlaid on top of the plant in full bloom
in summer.
And in the Early 20th Century
Prof. Cleveland Abbe, “Ice Columns in Gravelly Soil,” Monthly Weather
Review, 1905, 157-8, writes about needle ice and references LeConte, 1850. He notes that “Only once have I
seen the corresponding phenomenon of a thin ice sheet of parallel ice
columns exuding from a vertical crevice in the bark of a tree, many
beautiful examples of which are given by Professor LeConte
and Sir John Herschel.” Abbe rejects the explanation of LeConte and offers his own suppositions. He calls
for someone to repeat the process in the physical laboratory. There
is a concluding remark “This explanation of the growth of hollow columns of
ice in gravelly soil applies with slight changes to the hollow stems and
plates of snow crystals. The whole subject of the growth of
crystalline forms needs elucidation.” p. 158.
Then I found Coblentz, “The Exudation of Ice from Stems of Plants” in
the Journal of the Franklin Institute, 589-621, Nov 1914.
Coblentz was a physicist working for the National Bureau of Standards in Washington, DC.
In 1913 he found some frost flowers in Rock Creek
Park and started observing what he
saw. He systematically made observations, took notes and carried out
many experiments with the help of colleagues. He found that in the
mix of plants in the rocky slopes, the ice flowers occurred only on Cunila mariana,
or Dittany. He cut off stems and inserted them in moist soil, test
tubes and crucibles. He reported on how rapidly water moved up the
dry stems of Dittany and was able to grow ice ribbons, what he also called
ice fringes and ice filaments. He showed that the roots of the plant
are not necessary for the formation of ice, nor is the outer bark. He applied
different treatments to the stems and showed that the water for the ice
comes from within the stem and is not deposited from the air. He noted one
ice flower weighed 5 grams and observed that many were of this size.
Other than Schwalbe (1884) in the Harz Mountains,
Coblentz appears to be the only person who has systematically grown ice
ribbons and reported on them. (Mention should be made of Bruce Means,
The American Gardener, Jan/Feb 2005, 36, who mentioned he grew
beautiful ice flowers on stems of flat-seed sunflowers.) Coblentz has many
photos of the ribbons he grew, but the copy of his paper I saw was on
microfilm and the photos were not very clear. He has sketches of the
setup of his experiments and of some of the ice ribbons he grew and thus
Coblentz demonstrates the ice ribbons are a product of a physical
process. This is an important paper to understand the nature of these
ice formations because today many web sites attribute the ice to frozen
sap.
The Environments in Which Such
Ice Formations Are Found
But the process works only on the stems of particular plants.
Coblentz carried out his observations on Dittany, Cunila
mariana, which is now known as Cunila origanoides.
Many persons have observed that Frostweed (Verbesina virginica)
or White Crownbeard, produces such ice
ribbons. And, others write about Frostweed (Helianthemum
canadense) and note it produces these ice formations. I have seen
many examples of ice formations on Dittany and White Crownbeard,
but have not been able to find any photographic images of such ice on
frostweed Helianthemum canadense. But, I will continue to
look. Subsequently, I have found such ice formations on
other plants , as noted elsewhere.
LeConte (1850) wrote “The plants on which I
have observed it are two species of the genus Pluchea
of DeCandolle, or Conyza of the older
botanists, viz. Pluchea bifrons and P. camphorate.” I have not
been able to relate these species names to ice formations nor have I been
able to find new species names that were formerly known by these
names. I assume LeConte observed his ice
formations on one of the three species we know about today.
Herschel (1833) stated that he first saw such ice “. . . round the roots
and stumps of some dry and decaying thistles.” The second time he
found such ice on stumps of a bed of heliotropes but these stumps included
stems as he describes in his paper. I cannot tell what specific
plants were involved in the formation of these ice formations.
A. Hillefors wrote about “Needle Ice on Dead
and Rotten Branches” in Weather, 1976 (31, pp. 163-168). He
observed these in Sweden.
The photos I saw were on a poor quality photocopy. Then, in early
2006 I received an email and three photos from Wales showing flowers of ice
growing from rotten branches. In these photos the ice appears to be a
little more needle-like but it is quite attractive. Subsequently, I
have received photos of such ice on pieces of rotten wood on the ground
from a number of places in Europe and in one place in the USA.
These ice formations are not the same as Ice Flowers on stems extending up
from the ground. But, they occur under similar weather
conditions. These have been called Haareis,
Kammeis, Pipkrakes and
Silk Frost. I am certain these are the same ice formations Schwalbe
wrote about in 1884. We
now know this is Hair Ice.
Interestingly, while the ice formations based on dead and rotting wood
are mostly from Europe and the Pacific NW of America and the ice
flowers based on the stems of plants are mostly in the eastern part of the USA, there
is a photo of a classic ice ribbon on a stem on the cover of the Journal
of Glaciology (1993, 39:132). This photo was taken in northern India at
16,000 feet. Then in 2008 I received a link to another photo of an ice ribbon in
northern India. So, I must be
careful about making generalizations about what occurs where in our big
world.
In December 2006 I received an email from The Weather Doctor Kieth Heidorn who
referenced his web page where he has two photos of long and thin ice
ribbons that formed on a metal fence rail. The photos came from
Sheryl Terris of Vancouver Island, Canada. She is quoted as saying she
gets these ice formations year after year on the same gate. These appear to
be consistent with the observations of 1821 of similar ice formations on a
recently built stone wall. With her permission I put together a web page showing her great
photos. Then I experimented and was able to extrude ice
that is very similar to Sheryl's photos.
In summary, we know the formation of frost flowers, ice flowers or ice
ribbons is a physical process, not related to the growth of a biological
organism. These ice formations occur on the stems of a few species of
plants and on certain pieces of rotten wood on the ground. I thought
I could count the numbers of species on which these form, and then I hear
from a woman in central Tennessee
who found these on New York Ironweed Veronia
noveboracensis. She convinced me she
knew her plants and thus I added the stems of another plant on which these
occur. And, through these web pages I have heard from others and now have identified
about 40 plants on which these occur. I thought they occurred
only on dead stems, but last fall I saw them form on stems that we
alive.
There are probably more.
These form when the water in the soil remains above freezing while the
air temperature falls below freezing. The conditions would be optimal
on clear nights with no wind, when the dominant cooling process is net
radiation. This fits the description of many reports of observations
of ice ribbons, but, there are reports that these also occur under quite
windy conditions. See Tim Ernst: http://www.cloudland.net/Nov03journal/Nov03Journal.html
for the dates of 11/24/03 and 11/25/03.
The Tim Ernst story has evolved. See the link to his
archives at:
http://timernst.com/JournalArchives/journalarchives1.html
It appears that the images I referenced in the first
decade of the 20th Century are not currently available as of
2020. After observing these many times during the fall and winter of 2007 I
know the only criteria is air temperatures below freezing and a soil
temperature above freezing.
On the Processes of the Formation
of Ice Flowers, Frost Flowers and Ice Ribbons
What is the process that leads to the formation of these ribbons of
ice? The stems of these plants and certain rotten pieces of wood
serve as conduits to transmit water from the soil which is above freezing
to a surface which is below freezing. (I cannot conceive how a fence
rail could stay above freezing while the air outside is well below
freezing. I'm thinking about that.)
Charles Knight of UCAR offered an explanation in an email (2 Feb 05):
“The reason this sort of thing happens is that ice cannot grow in
supercooled water through very small openings, but water, of course, can
flow through the openings. So one can have an ice crystal in contact
with a wet porous material, and it grows at the contact, pushing the ice
crystal away while the supercooled water flows to the contact.” Based
on this there is another necessary condition for the formation of the ice
-- the dew point temperature of the air must be below freezing and the
temperature must fall to the dew point, or more properly the frost
point. When the temperature falls to the frost point, ice will start
to form on surfaces. The crystallization of the ice should be
sufficient to start the growth of ice flowers or Haareis,
etc.
Knight pointed me to the paper by Ozawa and Kinosite,
“Segregated Ice Growth on a Microporous Filter” Journal of Colloid and
Interface Science, (132: 1, 1989). They define ice segregation as
“. . . the phenomenon in which, through freezing, ice grows out from
moisture-containing porous material such as soil.” (p. 113). They
conducted experiments growing ice over many hours while making very
detailed measurements. They found the water to be supercooled and colder
than the surface where the ice forms. But, in their experiments they
started the freezing process by introducing a droplet of ice on the surface
of the porous filter. They show that the latent heat of fusion flows
from the surface of freezing to the supercooled water. They conclude
their paper by considering these processes in soils and the formation of
needle ice and/or ice wedges. They do not seem to be aware of ice
ribbons or frost flowers.
So, what we observe when we see ice flowers or frost flowers is ice
segregation along the stem of a plant. When the supercooled water
penetrating through the stem encounters the first crystals of frost the
supercooled water turns to ice. That process continues and new ice is added
at the stem-ice boundary. This pushes the old ice out and away from
the stem. If the stem is not ruptured over the night, then the
process can go on continuously until the ambient air temperature rises
above freezing or there is a limit to the supply of water in the soil.
I have observed that such ice flowers will reoccur on subsequent
nights showing that the water in the stems does not always freeze.
And, it is known that such ice formations may occur in the same area over
many nights in late fall and winter.
In fall 2007
I observed the rates at which such ice forms on stems of White crownbeard in my own yard. I show this by a
sequence of three photos over one night. Forrest Mims III has a
better record with a
time-lapse video on his YouTube site.
Thanks to the wide reach of the Internet, we are learning more day by
day. If you have observed the growth of these ice flowers, ribbons or
whatever you call them and can add insight into the process, please let me
know. jrcarter@ilstu.edu
|