Erratum: Anomalous region on Mars: implications for near-surface liquid water*

Nature ◽  
1980 ◽  
Vol 288 (5792) ◽  
pp. 735-738 ◽  
Author(s):  
S. H. Zisk ◽  
P. J. Mouginis-Mark
Keyword(s):  
Liquid Water ◽  
Near Surface ◽  
Surface Liquid ◽  
Anomalous Region

Anomalous region on Mars: implications for near-surface liquid water

Nature ◽  
1980 ◽  
Vol 288 (5787) ◽  
pp. 126-129 ◽  
Author(s):  
S. H. Zisk ◽  
P. J. Mouginis-Mark
Keyword(s):  
Liquid Water ◽  
Near Surface ◽  
Surface Liquid ◽  
Anomalous Region

scholarly journals Carbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Owen R. Lehmer ◽  
David C. Catling ◽  
Joshua Krissansen-Totton
Keyword(s):  
Liquid Water ◽  
Physicochemical Parameters ◽  
Silicate Weathering ◽  
Habitable Zone ◽  
Two Dimensional ◽  
Land Area ◽  
Incident Flux ◽  
Earth Like Planets ◽  
Surface Liquid ◽  
Log Linear

AbstractIn the conventional habitable zone (HZ) concept, a CO2-H2O greenhouse maintains surface liquid water. Through the water-mediated carbonate-silicate weathering cycle, atmospheric CO2 partial pressure (pCO2) responds to changes in surface temperature, stabilizing the climate over geologic timescales. We show that this weathering feedback ought to produce a log-linear relationship between pCO2 and incident flux on Earth-like planets in the HZ. However, this trend has scatter because geophysical and physicochemical parameters can vary, such as land area for weathering and CO2 outgassing fluxes. Using a coupled climate and carbonate-silicate weathering model, we quantify the likely scatter in pCO2 with orbital distance throughout the HZ. From this dispersion, we predict a two-dimensional relationship between incident flux and pCO2 in the HZ and show that it could be detected from at least 83 (2σ) Earth-like exoplanet observations. If fewer Earth-like exoplanets are observed, testing the HZ hypothesis from this relationship could be difficult.

scholarly journals Future surface mass balance and surface melt in the Amundsen sector of the West Antarctic Ice Sheet

2021 ◽  
Vol 15 (2) ◽  
pp. 571-593
Author(s):  
Marion Donat-Magnin ◽  
Nicolas C. Jourdain ◽  
Christoph Kittel ◽  
Cécile Agosta ◽  
Charles Amory ◽  
...  
Keyword(s):  
Mass Balance ◽  
Liquid Water ◽  
Ice Sheet ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Ice Shelves ◽  
Net Production ◽  
West Antarctic ◽  
Surface Liquid ◽  
Surface Melt

Abstract. We present projections of West Antarctic surface mass balance (SMB) and surface melt to 2080–2100 under the RCP8.5 scenario and based on a regional model at 10 km resolution. Our projections are built by adding a CMIP5 (Coupled Model Intercomparison Project Phase 5) multi-model-mean seasonal climate-change anomaly to the present-day model boundary conditions. Using an anomaly has the advantage to reduce CMIP5 model biases, and a perfect-model test reveals that our approach captures most characteristics of future changes despite a 16 %–17 % underestimation of projected SMB and melt rates. SMB over the grounded ice sheet in the sector between Getz and Abbot increases from 336 Gt yr−1 in 1989–2009 to 455 Gt yr−1 in 2080–2100, which would reduce the global sea level changing rate by 0.33 mm yr−1. Snowfall indeed increases by 7.4 % ∘C−1 to 8.9 % ∘C−1 of near-surface warming due to increasing saturation water vapour pressure in warmer conditions, reduced sea-ice concentrations, and more marine air intrusion. Ice-shelf surface melt rates increase by an order of magnitude in the 21st century mostly due to higher downward radiation from increased humidity and to reduced albedo in the presence of melting. There is a net production of surface liquid water over eastern ice shelves (Abbot, Cosgrove, and Pine Island) but not over western ice shelves (Thwaites, Crosson, Dotson, and Getz). This is explained by the evolution of the melt-to-snowfall ratio: below a threshold of 0.60 to 0.85 in our simulations, firn air is not entirely depleted by melt water, while entire depletion and net production of surface liquid water occur for higher ratios. This suggests that western ice shelves might remain unaffected by hydrofracturing for more than a century under RCP8.5, while eastern ice shelves have a high potential for hydrofracturing before the end of this century.

scholarly journals Morphological evidence for geologically young thaw of ice on Mars: A review of recent studies using high-resolution imaging data

2013 ◽  
Vol 37 (3) ◽  
pp. 289-324 ◽  
Author(s):  
M.R. Balme ◽  
C.J. Gallagher ◽  
E. Hauber
Keyword(s):  
Liquid Water ◽  
Morphological Evidence ◽  
Polar Regions ◽  
Imaging Data ◽  
Patterned Ground ◽  
Large Lakes ◽  
Near Surface ◽  
Crater Lakes ◽  
Recent Climate ◽  
Liquid Flows

Liquid water is generally only meta-stable on Mars today; it quickly freezes, evaporates or boils in the cold, dry, thin atmosphere (surface pressure is about 200 times lower than on Earth). Nevertheless, there is morphological evidence that surface water was extensive in more ancient times, including the Noachian Epoch (∼4.1 Ga to ∼3.7 Ga bp), when large lakes existed and river-like channel networks were incised, and early in the Hesperian Epoch (∼3.7 Ga to ∼2.9 Ga bp), when megafloods carved enormous channels and smaller fluvial networks developed in association with crater-lakes. However, by the Amazonian Epoch (∼3.0 Ga to present), most surface morphogenesis associated with liquid water had ceased, with long periods of water sequestration as ice in the near-surface and polar regions. However, inferences from observations using imaging data with sub-metre pixel sizes indicate that periglacial landscapes, involving morphogenesis associated with ground-ice and/or surface-ice thaw and liquid flows, has been active within the last few million years. In this paper, three such landform assemblages are described: a high-latitude assemblage comprising features interpreted to be sorted clastic stripes, circles and polygons, non-sorted polygonally patterned ground, fluvial gullies, and solifluction lobes; a mid-latitude assemblage comprising gullies, patterned ground, debris-covered glaciers and hillslope stripes; and an equatorial assemblage of linked basins, patterned ground, possible pingos, and channel-and-scarp features interpreted to be retrogressive thaw-slumps. Hypotheses to explain these observations are explored, including recent climate change, and hydrated minerals in the regolith ‘thawing’ to form liquid brines at very low temperatures. The use of terrestrial analogue field sites is also discussed.

A brief overview of photocatalytic mechanisms and pathways in water

2007 ◽  
Vol 55 (12) ◽  
pp. 167-173 ◽  
Author(s):  
P. Pichat
Keyword(s):  
Charge Transfer ◽  
Organic Pollutants ◽  
Liquid Water ◽  
Bound Water ◽  
Near Surface ◽  
Low Concentrations ◽  
Water Layers

This paper outlines the basic events that occur when a semiconductor, in contact with aerated liquid water containing low concentrations of pollutants, is photoexcited. First, the factors favouring this recombination of photoproduced charges are recalled, and the difficulties in decreasing the recombination are underlined. Second, the formation and identification of the species resulting from charge transfer with O2, H2O and pollutants are presented. Third, the reactions involving these species are considered, and methods for assessing their respective importance are critically reviewed. Fourth, on the basis of the view that the photocatalyst surface is covered by tightly bound water layers which hinder the adsorption of many organic pollutants, the hypothesis according to which primary photocatalytic events can take place within the near-surface solution layers is discussed.

scholarly journals On the probability of habitable planets

2013 ◽  
Vol 12 (3) ◽  
pp. 177-185 ◽  
Author(s):  
François Forget
Keyword(s):  
Liquid Water ◽  
Climate Models ◽  
Climatic Conditions ◽  
Point Of View ◽  
Habitable Zone ◽  
One Dimensional ◽  
The Past ◽  
Surface Liquid ◽  
New Generation ◽  
Global Mean

AbstractIn the past 15 years, astronomers have revealed that a significant fraction of the stars should harbour planets and that it is likely that terrestrial planets are abundant in our galaxy. Among these planets, how many are habitable, i.e. suitable for life and its evolution? These questions have been discussed for years and we are slowly making progress. Liquid water remains the key criterion for habitability. It can exist in the interior of a variety of planetary bodies, but it is usually assumed that liquid water at the surface interacting with rocks and light is necessary for emergence of a life able to modify its environment and evolve. The first key issue is thus to understand the climatic conditions allowing surface liquid water assuming a suitable atmosphere. These have been studied with global mean one-dimensional (1D) models which have defined the ‘classical habitable zone’, the range of orbital distances within which worlds can maintain liquid water on their surfaces (Kasting et al. 1993). A new generation of 3D climate models based on universal equations and tested on bodies in the solar system are now available to explore with accuracy climate regimes that could locally allow liquid water. The second key issue is now to better understand the processes which control the composition and the evolution of the atmospheres of exoplanets, and in particular the geophysical feedbacks that seem to be necessary to maintain a continuously habitable climate. From that point of view, it is not impossible that the Earth's case may be special and uncommon.

scholarly journals Seasonal monitoring of melt and accumulation within the deep percolation zone of the Greenland Ice Sheet and comparison with simulations of regional climate modeling

2018 ◽  
Author(s):  
Achim Heilig ◽  
Olaf Eisen ◽  
Michael MacFerrin ◽  
Marco Tedesco ◽  
Xavier Fettweis
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Pore Space ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Liquid Water Content ◽  
Water Infiltration ◽  
Near Surface ◽  
Percolation Zone

Abstract. Increasing melt over the Greenland ice sheet (GrIS) recorded over the past years has resulted in significant changes of the percolation regime of the ice sheet. It remains unclear whether Greenland's percolation zone will act as meltwater buffer in the near future through gradually filling all pore space or if near-surface refreezing causes the formation of impermeable layers, which provoke lateral runoff. Homogeneous ice layers within perennial firn, as well as near-surface ice layers of several meter thickness are observable in firn cores. Because firn coring is a destructive method, deriving stratigraphic changes in firn and allocation of summer melt events is challenging. To overcome this deficit and provide continuous data for model evaluations on snow and firn density, temporal changes in liquid water content and depths of water infiltration, we installed an upward-looking radar system (upGPR) 3.4 m below the snow surface in May 2016 close to Camp Raven (66.4779° N/46.2856° W) at 2120 m a.s.l. The radar is capable to monitor quasi-continuously changes in snow and firn stratigraphy, which occur above the antennas. For summer 2016, we observed four major melt events, which routed liquid water into various depths beneath the surface. The last event in mid-August resulted in the deepest percolation down to about 2.3 m beneath the surface. Comparisons with simulations from the regional climate model MAR are in very good agreement in terms of seasonal changes in accumulation and timing of onset of melt. However, neither bulk density of near-surface layers nor the amounts of liquid water and percolation depths predicted by MAR correspond with upGPR data. Radar data and records of a nearby thermistor string, in contrast, matched very well, for both, timing and depth of temperature changes and observed water percolations. All four melt events transferred a cumulative mass of 56 kg/m2 into firn beneath the summer surface of 2015. We find that continuous observations of liquid water content, percolation depths and rates for the seasonal mass fluxes are sufficiently accurate to provide valuable information for validation of model approaches and help to develop a better understanding of liquid water retention and percolation in perennial firn.

scholarly journals The modelled liquid water balance of the Greenland Ice Sheet

2017 ◽  
Author(s):  
Christian R. Steger ◽  
Carleen H. Reijmer ◽  
Michiel R. van den Broeke
Keyword(s):  
Water Balance ◽  
Liquid Water ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Special Focus ◽  
Southeastern Part ◽  
Upward Migration ◽  
Near Surface ◽  
Surface Mass ◽  
Surface Melt

Abstract. Recent studies indicate that the surface mass balance will dominate the Greenland Ice Sheet's (GrIS) contribution to 21st century sea level rise. Consequently, it is crucial to understand the liquid water balance (LWB) of the ice sheet and its response to increasing surface melt. We therefore analyse a firn simulation conducted with SNOWPACK for the GrIS and over the period 1960–2014 with a special focus on the LWB and refreezing. An indirect evaluation of the simulated refreezing climate with GRACE and firn temperature observations indicate a good model performance. Results of the LWB analysis reveal a spatially uniform increase in surface melt during 1990–2014. As a response, refreezing and runoff also indicate positive trends for this period, where refreezing increases with only half the rate of runoff, which implies that the majority of the additional liquid input runs off the ice sheet. However, this pattern is spatially variable as e.g. in the southeastern part of the GrIS, most of the additional liquid input is buffered in the firn layer due to relatively high snowfall rates. The increase in modelled refreezing leads to a general decrease in firn air content and to a substantial increase in near-surface firn temperature in some regions. On the western side of the ice sheet, modelled firn temperature increases are highest in the lower accumulation zone and are primarily caused by the exceptional melt season of 2012. On the eastern side, simulated firn temperature increases more gradually and with an associated upward migration of firn aquifers.

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