Needle Ice Formation Research Articles

Andean rolling mosses gather on stone pavements: Geoecology of Grimmia longirostris Hook. in a high periglacial páramo

Rolling mosses of Grimmia longirostris Hook. were studied in Páramo Piedras Blancas, a high Andean area in Venezuela, using a geoecological research framework focused on interactions between geomorphic, ecological, and soil processes. Spatial patterns of mosses were analyzed downslope from granitic outcrops on three slopes at 4445–4480 m elevation. Fragments from epilithic mosses on the apex outcrops were the source of other mosses. Distance of moss transport below rocks was measured at all sites; mosses on the gentlest (≤4°), 34 m-long, slope were censused along a belt transect on 17 contiguous quadrats; density of moss growth forms, stone size, percent of bare-soil cover, and surface soil properties were determined. Surface clast morphology and profile characteristics of a periglacial stone pavement at the slope base were also examined. Mosses on this site included four growth forms: epilithic mosses on outcrops; mobile, rolling moss balls; epilithic mosses on loose clasts; and unattached elongated mosses. Moss balls (density: ≤0.87 mosses/m2) lay on upper-transect plots over bare soils (≤92% cover) disturbed by needle ice. Soils here contained ~43–51% fine grains (≤0.063 mm) and 2.9–5.9% organic matter; this made them exceptionally prone to ice segregation and needle-ice formation. Lower-transect plots showed 78–100% stone cover—cobbles and blocks—but little exposed soil; mosses attached to loose clasts were exceedingly abundant (≤31/m2) on this section. Unattached elongated mosses, often resting along boundaries between adjacent stones, were also common (≤5.5/m2). The basal stone pavement showed a shallow (≤7 cm) rock veneer over a 24 cm-thick profile with exceptionally fine soil—up to 83.2% fine grains, ≤8.6% organic matter.A conceptual developmental model emphasizing the close linkages among the spatial distribution of mosses, patterns of surface clasts, and characteristics of soils and stone pavements is proposed: (i) Stones and mosses are transported downhill by needle ice and other frost agents; moss fragments gradually assume a globular shape, forming rolling moss balls. (ii) When these reach the stones and pavements on the basal slope, they cannot be transported any further, and remain immobile. (iii) Some mosses come to rest along boundaries between stones and develop into unattached elongated mosses or, (iv) they may become gradually attached to cobbles on the stone pavement; clasts with epilithic mosses can continue moving toward the basin floor. (v) Some mosses become fragmented and provide a source of elongated mosses, or remain partially attached to clasts. Stone pavements develop by a combination of rock accumulation following needle-ice transport, rock upheaving and sorting by ground frost, slope runoff, and downward soil illuviation.

Needle ice formation, induced frost heave, and frost creep: A case study through photogrammetry at Stelvio Pass (Italian Central Alps)

Needle ice growth is one of the more widespread and easily visible, but less studied, climate related processes shaping soil evolution, surface dynamics and ecosystem changes in the alpine environments. Here, we show the results of the monitoring of needle ice development at four plots located at 2670 m a.s.l. close to the Stelvio Pass in the Italian Central Alps during 2016. Needle Ice formation and evolution with time was monitored through the photogrammetric technique of the Structure from Motion (SfM). Our monitoring data included also quantitative measurements of some selected physical and climatic parameters like air temperature, ground temperature and ground water content at depths of 2 and 5 cm. Our data demonstrate that needle ice can develop with a relatively low ground water content (13.2%), at a relatively high minimum ground temperature (−0.3 °C) and with a low cooling rate (<1.8 °C h−1). Moreover, for the first time, we observed that needle ice can form below a thin snow cover (<25 mm) that can enhance the sensible heat flow from the ground to the atmosphere and, therefore, promote the cooling of the near surface ground. Statistically, the minimum air temperature results in the leading factor for the needle ice growth.The total frost heave seems to be related to the abundance of fine material (although we couldn't demonstrate it statistically). The absence of statistically significant relationships between frost heave and frost creep could be probably due to the importance of the observed needle ice toppling and the possible sliding of the clasts during the melting phases.

Diurnal to Decadal Changes in the Balance between Vegetation and Bare Ground in Tasmanian Fjaeldmark

ABSTRACTPeriglacial processes are active under current climatic conditions on the more exposed peaks and ridges of Tasmania’s high country. Non-sorted steps, stripes, and solifluction lobes with vegetated risers and bare treads have formed on many of the mountains capped in fissile sedimentary rocks. Any disturbance to the balance between vegetation and bare ground can result in biogeomorphic feedbacks leading to an increase or decrease in periglacial activity and thereby threaten the survival of fjaeldmark. We tested the hypotheses that vegetation helps create risers by capturing material moved by needle ice, water, and wind, and that the balance between vegetation and bare ground in fjaeldmark is dynamic in Tasmania at the decadal time scale. Repeat photo plots and temperature data loggers were employed to monitor the dynamism of two non-sorted lobes on Mount Rufus over a seven-month period. Diurnal freeze/thaw cycles resulted in needle ice formation on the bare treads and promoted downslope movement of the surface layer through frost creep. Vegetation was observed to reduce geomorphic activity and to capture soil and clasts transported downslope, thereby steepening the risers. Aerial photographic analysis showed a 0.065% per annum increase in vegetation cover in fjaeldmark since the mid-20th century. Mountains that had a high number of days with snow cover were especially prone to increases in vegetation cover. Decline in vegetation cover occurred on some mountains burned during the past century. The smallest changes occurred on the most exposed peaks and ridges.

Effects of freezing on microstructure and rehydration properties of freeze-dried soybean curd

Ice crystallization controls the microstructure and subsequent mass transport of water in freeze-dried food matrices. This study investigated the effects of freezing on the microstructure and rehydration properties of porous, freeze-dried soybean curd. Soybean curd was prefrozen at various freezing conditions (−20 °C, −50 °C, −90 °C and in Liq.N2) prior to freeze-drying. Scanning electron microscopy showed a correlation between pore morphologies and freezing temperatures. The patterns of ice formed in the 3-D matrices were revealed using X-ray computed tomography. The decreased freezing temperature from −20 °C to −90 °C gave clearer needle ice formation in parallel with heat transfer resulting in a sponge-like structure after rehydration with a corresponding wall thickness of 2.9–21.8 μm. Conversely, the Liq.N2 freezing gave very fine ice crystals which effectively retained the fresh-soybean curd structure and color upon rehydration. Cracking increased with decreased freezing temperatures which also accelerated solid loss during rehydration. A correlation between the pore morphology (i.e. pore diameter and 1st-order rehydration kinetics) was observed. Cluster analysis revealed that freezing at −20 °C and −50 °C changed the color; whereas, freezing at −90 °C and with Liq.N2 effectively preserved the color of the rehydrated soybean curd. The results clearly demonstrated a process-structure-function relationship in freeze-drying which can be effectively utilized in the structural design of freeze-dried food materials.

First observations on needle ice formation in the sub-Antarctic

First observations on needle ice formation in the sub-Antarctic

A acção dos pipekrakes na morfogénese actual na Serra do Gerês

NEEDLE ICE EROSION IN THE SERRA DO GERÊS (NW PORTUGAL)- After a short review of the studies on needle ice in the world, its morphogenetic significance in the Serra do Gerês is discussed. Several needle ice induced morphological features were identified in the field. Nevertheless, cryogenic features are in most cases ephemeral, being destroyed by the action of processes with higher morphogenetic capacity (i.e. runoff). Needle ice acts mostly as a disruptive agent, causing the desagregation of weathered granite or other non-choesive deposits. The resultant material is easily transported by other processes, like runoff or wind. The more prone areas to needle ice formation are also discussed.

Some effects of giant Andean stem-rosettes on ground microclimate, and their ecological significance

The effect of giant Andean stem-rosettes (Coespeletia lutescens) on air and soil temperatures was studied in the Paramo de Piedras Blancas (Venezuela) at 4265 and 4385 m altitude during the dry season, which is the coldest season in this tropical mountain area. Maximum air temperatures beneath a plant canopy were only slightly higher than in the open. Minimum temperatures below the stem-rosettes were 4.7° to 7.0°C higher than in the open. This substantially reduced the intensity of nightly freezing. Soil temperature minima at 20 cm depth were 2.4° to 4.2°C higher below plants, but maxima were somewhat lower than in bare soil. These microclimatic alterations are ecologically significant for stemprosette seedlings, which should have a higher probability of survival due to the reduced frequency of frost and needle ice formation below large plants. Warmer soils at night should also result in greater water uptake by seedlings during the early morning hours, thus reducing dry-season mortality.

Small-Scale Testing of Soils for Frost Action

Abstract A method is described for convenient study of frost action, including soil heaving and needle ice formation. The apparatus is simple and small and the procedure requires only 25-cm3 soil specimens. The method could be useful for screening either large numbers or limited quantities of soils or soil additives for frost susceptibility. The method described was used to perform a limited number of tests with several soils. The tests obtained action in the form of soil heave, ice heave, or ice needles, yielding maximum heights up to three to six times the initial 40-mm soil depth. Maximum growth rates were up to 1 to 3 mm/h for soil heaves and 3 to 7 or more mm/h for ice heaves and ice needles. Initial trials showed that thickener additives and possibly other treatments can restrict frost action.