The initiation of modern soft and hard Snowball Earth climates in CCSM4

Abstract. Geochemical and geological evidence suggested that several global-scale glaciation events occurred during the Neoproterozoic era at 750–580 million years ago. The initiation of these glaciations is thought to have been a consequence of the combined influence of a result of low-level carbon dioxide and an approximately 6% weakening of solar luminosity. The latest version of the Community Climate System Model (CCSM4) is employed herein to explore the detailed combination of forcings required to trigger such extreme glaciation under present-day geography and topography conditions. It is found that runaway glaciation occurs in the model under the following conditions: (1) a 8–9% reduction in solar radiation with 286 ppmv CO2 or (2) a 6% reduction in solar radiation with 70–100 ppmv CO2. These thresholds are only moderately different from those found to be characteristic of the previous CCSM3 model reported recently in Yang et al. (2011a,b) for which the respective critical points corresponded to a 10–10.5% reduction in solar radiation with 286 ppmv CO2 or a 6% reduction in solar radiation with 17.5–20 ppmv CO2. The most important reason for these differences is that the sea-ice/snow albedo in CCSM4 is somewhat higher than in CCSM3. Differences in cloud radiative forcings and oceanic and atmospheric heat transports between CCSM3 and CCSM4 also influence the bifurcation points. The forcings required to trigger a "hard Snowball" Earth in either CCSM3 or CCSM4 may be not met by the conditions expected to be characteristic of the Neoproterozoic. Furthermore, there exist "soft Snowball" Earth states, in which the sea-ice coverage reaches approximately 60–65%, land masses in low latitudes are covered by perennial snow, and runaway glaciation does not develop. This is also qualitatively consistent with our previous results of the CCSM3 model. These results suggest that a "soft Snowball" solution for the Neoproterozoic is entirely plausible and may in fact be preferred.

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The initiation of modern soft and hard Snowball Earth climates in CCSM4

Climate of the Past ◽

10.5194/cp-8-907-2012 ◽

2012 ◽

Vol 8 (3) ◽

pp. 907-918 ◽

Cited By ~ 29

Author(s):

J. Yang ◽

W. R. Peltier ◽

Y. Hu

Keyword(s):

Solar Radiation ◽

Sea Ice ◽

Atmospheric Carbon Dioxide ◽

Carbon Dioxide Concentration ◽

Global Scale ◽

Snowball Earth ◽

Climate System Model ◽

Geological Evidence ◽

Radiative Forcings ◽

The Impact

Abstract. Geochemical and geological evidence has suggested that several global-scale glaciation events occurred during the Neoproterozoic Era in the interval from 750–580 million years ago. The initiation of these glaciations is thought to have been a consequence of the combined influence of a low level of atmospheric carbon dioxide concentration and an approximately 6% weakening of solar luminosity. The latest version of the Community Climate System Model (CCSM4) is employed herein to explore the detailed combination of forcings required to trigger such extreme glaciation conditions under present-day circumstances of geography and topography. It is found that runaway glaciation occurs in the model under the following conditions: (1) an 8–9% reduction in solar radiation with 286 ppmv CO2 or (2) a 6% reduction in solar radiation with 70–100 ppmv CO2. These thresholds are moderately different from those found to be characteristic of the previously employd CCSM3 model reported recently in Yang et al. (2012a,b), for which the respective critical points corresponded to a 10–10.5% reduction in solar radiation with 286 ppmv CO2 or a 6% reduction in solar radiation with 17.5–20 ppmv CO2. The most important reason for these differences is that the sea ice/snow albedo parameterization employed in CCSM4 is believed to be more realistic than that in CCSM3. Differences in cloud radiative forcings and ocean and atmosphere heat transports also influence the bifurcation points. These results are potentially very important, as they are to serve as control on further calculations which will be devoted to an investigation of the impact of continental configuration. We demonstrate that there exist ''soft Snowball'' Earth states, in which the fractional sea ice coverage reaches approximately 60–65%, land masses in low latitudes are covered by perennial snow, and runaway glaciation does not develop. This is consistent with our previous results based upon CCSM3. Although our results cannot exclude the possibility of a ''hard Snowball'' solution, it is suggested that a ''soft Snowball'' solution for the Neoproterozoic remains entirely plausible.

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The Initiation of Modern “Soft Snowball” and “Hard Snowball” Climates in CCSM3. Part I: The Influences of Solar Luminosity, CO2 Concentration, and the Sea Ice/Snow Albedo Parameterization

Journal of Climate ◽

10.1175/jcli-d-11-00189.1 ◽

2012 ◽

Vol 25 (8) ◽

pp. 2711-2736 ◽

Cited By ~ 45

Author(s):

Jun Yang ◽

W. Richard Peltier ◽

Yongyun Hu

Keyword(s):

Solar Radiation ◽

Sea Ice ◽

Open Water ◽

Co2 Concentration ◽

Critical Conditions ◽

Climate System Model ◽

Snow Albedo ◽

Solar Luminosity ◽

The Earth ◽

Continental Ice Sheets

Abstract The “Snowball Earth” hypothesis, proposed to explain the Neoproterozoic glacial episodes in the period 750–580 million years ago, suggested that the earth was globally covered by ice/snow during these events. This study addresses the problem of the forcings required for the earth to enter such a state of complete glaciation using the Community Climate System Model, version 3 (CCSM3). All of the simulations performed to address this issue employ the geography and topography of the present-day earth and are employed to explore the combination of factors consisting of total solar luminosity, CO2 concentration, and sea ice/snow albedo parameterization that would be required for such an event to occur. The analyses demonstrate that the critical conditions beyond which runaway ice–albedo feedback will lead to global freezing include 1) a 10%–10.5% reduction in solar radiation with preindustrial greenhouse gas concentrations; 2) a 6% reduction in solar radiation with 17.5 ppmv CO2; or 3) 6% less solar radiation and 286 ppmv CO2 if sea ice albedo is equal to or greater than 0.60 with a snow albedo of 0.78, or if sea ice albedo is 0.58 with a snow albedo equal to or greater than 0.80. These bifurcation points are very sensitive to the sea ice and snow albedo parameterizations. Moreover, “soft Snowball” solutions are found in which tropical open water oceans stably coexist with year-round snow-covered low-latitude continents, implying that tropical continental ice sheets would actually be present. The authors conclude that a “soft Snowball” is entirely plausible, in which the global sea ice fraction may reach as high as 76% and sea ice margins may extend to 10°S(N) latitudes.

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A biologically driven directional change in susceptibility to global-scale glaciation during the Precambrian-Cambrian transition

10.1101/359422 ◽

2018 ◽

Author(s):

Richard A. Boyle ◽

Carolin R. Löscher

Keyword(s):

Land Surface ◽

Climate Models ◽

Abiotic Factors ◽

Global Scale ◽

Snowball Earth ◽

Critical Aspect ◽

Geological Evidence ◽

Directional Change ◽

Temperature Window ◽

Tectonic Boundary

Integrated geological evidence suggests that grounded ice sheets occurred at sea level across all latitudes during two intervals within the Neoproterozoic era; the “snowball Earth” (SBE) events. Glacial events at ~730 and ~650 million years ago (Ma) were probably followed by a less severe but nonetheless global-scale glaciation at ~580Ma, immediately preceding the proliferation of the first fossils exhibiting unambiguous animal-like form. Existing modelling identifies weathering-induced CO2 draw-down as a critical aspect of glacial inception, but ultimately attributes the SBE phenomenon to unusual tectonic boundary conditions. Here we suggest that the evident directional decrease in Earth’s susceptibility to a SBE suggests that such a-directional abiotic factors are an insufficient explanation for the lack of SBE events since ~580 Ma. Instead we hypothesize that the terrestrial biosphere’s capacity to sustain a given level of biotic weathering-enhancement under suboptimal/declining temperatures, itself decreased over time: because lichens (with a relatively robust tolerance of sub-optimal temperatures) were gradually displaced on the land surface by more complex photosynthetic life (with a narrower temperature window for growth). We use a simple modelling exercise to highlight the critical (but neglected) importance of the temperature sensitivity of the biotic weathering enhancement factor and discuss the likely values of key parameters in relation to both experiments and the results of complex climate models. We show how the terrestrial biosphere’s capacity to sustain a given level of silicate-weathering-induced CO2 draw-down is critical to the temperature/greenhouse forcing at which SBE initiation is conceivable. We do not dispute the importance of low degassing rate and other tectonic factors, but propose that the unique feature of the Neoproterozoic was biology’s capacity to tip the system over the edge into a runaway ice-albedo feedback; compensating for the self-limiting decline in weathering rate during the temperature decrease on the approach to glaciation. Such compensation was more significant in the Neoproterozoic than the Phanerozoic due, ultimately, to changes in the species composition of the weathering interface over the course of evolutionary time.

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Signature of the 27-day oscillation in the MLT tides and its relation with solar radiation at low latitudes

Earth Planets and Space ◽

10.1186/s40623-020-01149-7 ◽

2020 ◽

Vol 72 (1) ◽

Author(s):

Amitava Guharay ◽

Paulo Prado Batista ◽

Ricardo Arlen Buriti ◽

Nelson Jorge Schuch

Keyword(s):

Solar Radiation ◽

Low Latitudes

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Constraining Neoproterozoic subtropical low-level clouds to assess the plausibility of near-Snowball Earth states

10.5194/egusphere-egu21-4742 ◽

2021 ◽

Author(s):

Christoph Braun ◽

Aiko Voigt ◽

Johannes Hörner ◽

Joaquim G. Pinto

Keyword(s):

Sea Ice ◽

Climate Models ◽

Global Climate ◽

Global Climate Models ◽

Mixed Phase ◽

Snowball Earth ◽

Stable Range ◽

Climate Regime ◽

Low Level ◽

Mixed Phase Clouds

<p>Stable waterbelt climate states with close to global ice cover challenge the classical Snowball Earth hypothesis because they provide a robust explanation for the survival of advanced marine species during the Neoproterozoic glaciations (1000 &#8211; 541 Million years ago). Whether Earth&#8217;s climate stabilizes in a waterbelt state or rushes towards a Snowball state is determined by the magnitude of the ice-albedo feedback in the subtropics, where dark, bare sea ice instead of snow-covered sea ice prevails. For a given bare sea-ice albedo, the subtropical ice-albedo feedback and thus the stable range of the waterbelt climate regime is sensitive to the albedo over ice-free ocean, which is largely determined by shortwave cloud-radiative effects (CRE). In the present-day climate, CRE are known to dominate the spread of climate sensitivity across global climate models. We here study the impact of uncertainty associated with CRE on the existence of geologically relevant waterbelt climate regimes using two global climate models and an idealized energy balance model. We find that the stable range of the waterbelt climate regime is very sensitive to the abundance of subtropical low-level mixed-phase clouds. If subtropical cloud cover is low, climate sensitivity becomes so high as to inhibit stable waterbelt states.</p><p>The treatment of mixed-phase clouds is highly uncertain in global climate models. Therefore we aim to constrain the uncertainty associated with their CRE by means of a hierarchy of global and regional simulations that span horizontal grid resolutions from 160 km to 300m, and in particular include large eddy simulations of subtropical mixed-phase clouds located over a low-latitude ice edge. In the cold waterbelt climate subtropical CRE arise from convective events caused by strong meridional temperature gradients and stratocumulus decks located in areas of large-scale descending motion. We identify the latter to dominate subtropical CRE and therefore focus our large eddy simulations on subtropical stratocumulus clouds. By conducting simulations with two extreme scenarios for the abundance of atmospheric mineral dust, which serves as ice-nucleating particles and therefore can control mixed-phase cloud physics, we aim to estimate the possible spread of CRE associated with subtropical mixed-phase clouds. From this estimate we may assess whether Neoproterozoic low-level cloud abundance may have been high enough to sustain a stable waterbelt climate regime.</p>

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Connecting Antarctic Sea Ice and Mid-latitude Precipitation

10.5194/egusphere-egu21-16393 ◽

2021 ◽

Author(s):

Tristan Rendfrey ◽

Ashley Payne

Keyword(s):

Sea Ice ◽

Southern Hemisphere ◽

Reanalysis Data ◽

Lower Latitude ◽

Sea Ice Extent ◽

Weather Patterns ◽

Antarctic Sea Ice ◽

Ice Coverage ◽

Precipitation Timing ◽

Analogous Relation

<div><span>Climatic changes induce many significant changes to long standing weather patterns. These mechanisms interact to drive consequences that may not be immediately obvious. One such connection involves the apparent relationship between polar sea ice extent and mid-latitude precipitation timing and location. This correlation, its mechanisms, and possible influences on weather are decently understood with respect to the Northern Hemisphere. However, the analogous relation for the Southern Hemisphere has been less studied. This provides an opportunity to examine connections between polar conditions and mid-latitude weather.</span></div><div>&#160;</div><div><span>We explore the teleconnection between sea ice extent and lower latitude precipitation over the Southern Hemisphere. We investigate this relationship through observations of sea ice coverage using ICESat and ICESat-2 compared with reanalysis data via MERRA-2 in order to understand the variability of sea ice extent and its impact on midlatitude precipitation over the Southern Hemisphere. This study particularly examines the importance of seasonality and regional variations of the relationship.</span></div>

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What Do Global Climate Models Tell Us about Future Arctic Sea Ice Coverage Changes?

Climate ◽

10.3390/cli8010015 ◽

2020 ◽

Vol 8 (1) ◽

pp. 15 ◽

Cited By ~ 1

Author(s):

Ge Peng ◽

Jessica L. Matthews ◽

Muyin Wang ◽

Russell Vose ◽

Liqiang Sun

Keyword(s):

Sea Ice ◽

Climate Models ◽

Climate Adaptation ◽

Global Climate ◽

Arctic Sea Ice ◽

Global Climate Models ◽

Climate Projections ◽

Emission Scenarios ◽

Ice Coverage ◽

Arctic Sea

The prospect of an ice-free Arctic in our near future due to the rapid and accelerated Arctic sea ice decline has brought about the urgent need for reliable projections of the first ice-free Arctic summer year (FIASY). Together with up-to-date observations and characterizations of Arctic ice state, they are essential to business strategic planning, climate adaptation, and risk mitigation. In this study, the monthly Arctic sea ice extents from 12 global climate models are utilized to obtain projected FIASYs and their dependency on different emission scenarios, as well as to examine the nature of the ice retreat projections. The average value of model-projected FIASYs is 2054/2042, with a spread of 74/42 years for the medium/high emission scenarios, respectively. The earliest FIASY is projected to occur in year 2023, which may not be realistic, for both scenarios. The sensitivity of individual climate models to scenarios in projecting FIASYs is very model-dependent. The nature of model-projected Arctic sea ice coverage changes is shown to be primarily linear. FIASY values predicted by six commonly used statistical models that were curve-fitted with the first 30 years of climate projections (2006–2035), on other hand, show a preferred range of 2030–2040, with a distinct peak at 2034 for both scenarios, which is more comparable with those from previous studies.

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Global ocean dimethyl sulfide climatology estimated from observations and an artificial neural network

10.5194/bg-2020-72 ◽

2020 ◽

Author(s):

Wei-Lei Wang ◽

Guisheng Song ◽

François Primeau ◽

Eric S. Saltzman ◽

Thomas G. Bell ◽

...

Keyword(s):

Neural Network ◽

Artificial Neural Network ◽

Solar Radiation ◽

Mixed Layer ◽

Dimethyl Sulfide ◽

Mixed Layer Depth ◽

Environmental Parameters ◽

Global Scale ◽

Global Ocean ◽

Layer Depth

Abstract. Marine dimethyl sulfide (DMS) is important to climate due to the ability of DMS to alter Earth's radiation budget. However, a knowledge of the global-scale distribution, seasonal variability, and sea-to-air flux of DMS is needed in order to understand the factors controlling surface ocean DMS and its impact on climate. Here we examine the use of an artificial neural network (ANN) to extrapolate available DMS measurements to the global ocean and produce a global climatology with monthly temporal resolution. A global database of 57 810 ship-based DMS measurements in surface waters was used along with a suite of environmental parameters consisting of lat-lon coordinates, time-of-day, time-of-year, solar radiation, mixed layer depth, sea surface temperature, salinity, nitrate, phosphate, silicate, and oxygen. Linear regressions of DMS against the environmental parameters show that on a global scale mixed layer depth and solar radiation are the strongest predictors of DMS, however, they capture 14 % and 12 % of the raw DMS data variance, respectively. The multi-linear regression can capture more (∼29 %) of the raw data variance, but strongly underestimates high DMS concentrations. In contrast, the ANN captures ~61 % of the raw data variance in our database. Like prior climatologies our results show a strong seasonal cycle in DMS concentration and sea-to-air flux. The highest concentrations (fluxes) occur in the high-latitude oceans during the summer. We estimate a lower global sea-to-air DMS flux (17.90 &pm; 0.34 Tg S yr−1) than the prior estimate based on a map interpolation method when the same gas transfer velocity parameterization is used.

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Antarctic sea ice variability and trends, 1979–2010

The Cryosphere Discussions ◽

10.5194/tcd-6-931-2012 ◽

2012 ◽

Vol 6 (2) ◽

pp. 931-956 ◽

Cited By ~ 16

Author(s):

C. L. Parkinson ◽

D. J. Cavalieri

Keyword(s):

Indian Ocean ◽

Sea Ice ◽

Ross Sea ◽

Ice Cover ◽

Weddell Sea ◽

The Arctic ◽

Future Research ◽

Positive Trend ◽

Antarctic Sea Ice ◽

Ice Coverage

Abstract. In sharp contrast to the decreasing sea ice coverage of the Arctic, in the Antarctic the sea ice cover has, on average, expanded since the late 1970s. More specifically, satellite passive-microwave data for the period November 1978–December 2010 reveal an overall positive trend in ice extents of 17 100 ± 2300 km2 yr−1. Much of the increase, at 13 700 ± 1500 km2 yr−1, has occurred in the region of the Ross Sea, with lesser contributions from the Weddell Sea and Indian Ocean. One region, that of the Bellingshausen/Amundsen Seas, has, like the Arctic, instead experienced significant sea ice decreases, with an overall ice extent trend of −8200 ± 1200 km2 yr−1. When examined through the annual cycle over the 32-yr period 1979–2010, the Southern Hemisphere sea ice cover as a whole experienced positive ice extent trends in every month, ranging in magnitude from a low of 9100 ± 6300 km2 yr−1 in February to a high of 24 700 ± 10 000 km2 yr−1 in May. The Ross Sea and Indian Ocean also had positive trends in each month, while the Bellingshausen/Amundsen Seas had negative trends in each month, and the Weddell Sea and Western Pacific Ocean had a mixture of positive and negative trends. Comparing ice-area results to ice-extent results, in each case the ice-area trend has the same sign as the ice-extent trend, but differences in the magnitudes of the two trends identify regions with overall increasing ice concentrations and others with overall decreasing ice concentrations. The strong pattern of decreasing ice coverage in the Bellingshausen/Amundsen Seas region and increasing ice coverage in the Ross Sea region is suggestive of changes in atmospheric circulation. This is a key topic for future research.

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Influence of Seasonal Environmental Variables on the Distribution of Presumptive Fecal Coliforms around an Antarctic Research Station

Applied and Environmental Microbiology ◽

10.1128/aem.69.8.4884-4891.2003 ◽

2003 ◽

Vol 69 (8) ◽

pp. 4884-4891 ◽

Cited By ~ 38

Author(s):

Kevin A. Hughes

Keyword(s):

Environmental Factors ◽

Solar Radiation ◽

Sea Ice ◽

Fecal Coliform ◽

Algal Blooms ◽

Austral Summer ◽

Fecal Coliforms ◽

Late Winter ◽

Research Station ◽

The Antarctic

ABSTRACT Factors affecting fecal microorganism survival and distribution in the Antarctic marine environment include solar radiation, water salinity, temperature, sea ice conditions, and fecal input by humans and local wildlife populations. This study assessed the influence of these factors on the distribution of presumptive fecal coliforms around Rothera Point, Adelaide Island, Antarctic Peninsula during the austral summer and winter of February 1999 to September 1999. Each factor had a different degree of influence depending on the time of year. In summer (February), although the station population was high, presumptive fecal coliform concentrations were low, probably due to the biologically damaging effects of solar radiation. However, summer algal blooms reduced penetration of solar radiation into the water column. By early winter (April), fecal coliform concentrations were high, due to increased fecal input by migrant wildlife, while solar radiation doses were low. By late winter (September), fecal coliform concentrations were high near the station sewage outfall, as sea ice formation limited solar radiation penetration into the sea and prevented wind-driven water circulation near the outfall. During this study, environmental factors masked the effect of station population numbers on sewage plume size. If sewage production increases throughout the Antarctic, environmental factors may become less significant and effective sewage waste management will become increasingly important. These findings highlight the need for year-round monitoring of fecal coliform distribution in Antarctic waters near research stations to produce realistic evaluations of sewage pollution persistence and dispersal.

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