Warm early Mars surface enabled by high-altitude water ice clouds

Despite receiving just 30% of the Earth’s present-day insolation, Mars had water lakes and rivers early in the planet’s history, due to an unknown warming mechanism. A possible explanation for the >102-y-long lake-forming climates is warming by water ice clouds. However, this suggested cloud greenhouse explanation has proved difficult to replicate and has been argued to require unrealistically optically thick clouds at high altitudes. Here, we use a global climate model (GCM) to show that a cloud greenhouse can warm a Mars-like planet to global average annual-mean temperature (T¯) ∼265 K, which is warm enough for low-latitude lakes, and stay warm for centuries or longer, but only if the planet has spatially patchy surface water sources. Warm, stable climates involve surface ice (and low clouds) only at locations much colder than the average surface temperature. At locations horizontally distant from these surface cold traps, clouds are found only at high altitudes, which maximizes warming. Radiatively significant clouds persist because ice particles sublimate as they fall, moistening the subcloud layer so that modest updrafts can sustain relatively large amounts of cloud. The resulting climates are arid (area-averaged surface relative humidity ∼25%). In a warm, arid climate, lakes could be fed by groundwater upwelling, or by melting of ice following a cold-to-warm transition. Our results are consistent with the warm and arid climate favored by interpretation of geologic data, and support the cloud greenhouse hypothesis.

Download Full-text

Obliquity forcing of low-latitude climate

Climate of the Past Discussions ◽

10.5194/cpd-11-221-2015 ◽

2015 ◽

Vol 11 (1) ◽

pp. 221-241 ◽

Cited By ~ 4

Author(s):

J. H. C. Bosmans ◽

F. J. Hilgen ◽

E. Tuenter ◽

L. J. Lourens

Keyword(s):

High Latitude ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Rotational Axis ◽

Low Latitude ◽

Low Latitudes ◽

Paleoclimate Records ◽

Induced Changes ◽

The Tropics

Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical paleoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, implying that this gradient may be used to explain obliquity signals in low-latitude paleoclimate records instead of the classic 65° N summer insolation curve.

Download Full-text

A coupled atmosphere–hydrosphere global climate model of early Mars: A ‘cool and wet’ scenario for the formation of water channels

Icarus ◽

10.1016/j.icarus.2019.113567 ◽

2020 ◽

Vol 338 ◽

pp. 113567 ◽

Cited By ~ 5

Author(s):

A. Kamada ◽

T. Kuroda ◽

Y. Kasaba ◽

N. Terada ◽

H. Nakagawa ◽

...

Keyword(s):

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Water Channels ◽

Early Mars

Download Full-text

Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731620 ◽

2018 ◽

Vol 612 ◽

pp. A86 ◽

Cited By ~ 62

Author(s):

Martin Turbet ◽

Emeline Bolmont ◽

Jeremy Leconte ◽

François Forget ◽

Franck Selsis ◽

...

Keyword(s):

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Planetary Science ◽

Water Ice ◽

Planetary Evolution ◽

Ice Surface ◽

Surface Condensation ◽

Synchronous Rotation ◽

Ice Shell

TRAPPIST-1 planets are invaluable for the study of comparative planetary science outside our solar system and possibly habitability. Both transit timing variations (TTV) of the planets and the compact, resonant architecture of the system suggest that TRAPPIST-1 planets could be endowed with various volatiles today. First, we derived from N-body simulations possible planetary evolution scenarios, and show that all the planets are likely in synchronous rotation. We then used a versatile 3D global climate model (GCM) to explore the possible climates of cool planets around cool stars, with a focus on the TRAPPIST-1 system. We investigated the conditions required for cool planets to prevent possible volatile species to be lost permanently by surface condensation, irreversible burying or photochemical destruction. We also explored the resilience of the same volatiles (when in condensed phase) to a runaway greenhouse process. We find that background atmospheres made of N2, CO, or O2are rather resistant to atmospheric collapse. However, even if TRAPPIST-1 planets were able to sustain a thick background atmosphere by surviving early X/EUV radiation and stellar wind atmospheric erosion, it is difficult for them to accumulate significant greenhouse gases like CO2, CH4, or NH3. CO2can easily condense on the permanent nightside, forming CO2ice glaciers that would flow toward the substellar region. A complete CO2ice surface cover is theoretically possible on TRAPPIST-1g and h only, but CO2ices should be gravitationally unstable and get buried beneath the water ice shell in geologically short timescales. Given TRAPPIST-1 planets large EUV irradiation (at least ~103 × Titan’s flux), CH4and NH3are photodissociated rapidly and are thus hard to accumulate in the atmosphere. Photochemical hazes could then sedimentate and form a surface layer of tholins that would progressively thicken over the age of the TRAPPIST-1 system. Regarding habitability, we confirm that few bars of CO2would suffice to warm the surface of TRAPPIST-1f and g above the melting point of water. We also show that TRAPPIST-1e is a remarkable candidate for surface habitability. If the planet is today synchronous and abundant in water, then it should very likely sustain surface liquid water at least in the substellar region, whatever the atmosphere considered.

Download Full-text

Obliquity forcing of low-latitude climate

Climate of the Past ◽

10.5194/cp-11-1335-2015 ◽

2015 ◽

Vol 11 (10) ◽

pp. 1335-1346 ◽

Cited By ~ 38

Author(s):

J. H. C. Bosmans ◽

F. J. Hilgen ◽

E. Tuenter ◽

L. J. Lourens

Keyword(s):

High Latitude ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Rotational Axis ◽

Tropical Circulation ◽

Low Latitude ◽

Low Latitudes ◽

Induced Changes ◽

The Tropics

Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical palaeoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two idealized experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, suggesting that this gradient may be used to explain obliquity signals in low-latitude palaeoclimate records instead of the classical 65° N summer insolation curve.

Download Full-text

Testing the impact heating hypothesis for early Mars with a 3-D global climate model

Icarus ◽

10.1016/j.icarus.2019.04.005 ◽

2019 ◽

Vol 330 ◽

pp. 169-188 ◽

Cited By ~ 10

Author(s):

Kathryn Steakley ◽

James Murphy ◽

Melinda Kahre ◽

Robert Haberle ◽

Alexandre Kling

Keyword(s):

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Early Mars ◽

Impact Heating ◽

The Impact

Download Full-text

Correction to “Global climate model high-obliquity solutions to the ancient climate puzzles of the Faint-Young Sun Paradox and low-latitude Proterozoic Glaciation” by Gregory S. Jenkins

Journal of Geophysical Research Atmospheres ◽

10.1029/2000jd900225 ◽

2000 ◽

Vol 105 (D10) ◽

pp. 12519-12519

Author(s):

Gregory S. Jenkins

Keyword(s):

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Low Latitude

Download Full-text

Additional Global Climate Cooling by Clouds due to Ice Crystal Complexity

10.5194/acp-2018-491 ◽

2018 ◽

Author(s):

Emma Järvinen ◽

Olivier Jourdan ◽

David Neubauer ◽

Bin Yao ◽

Chao Liu ◽

...

Keyword(s):

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Ice Crystals ◽

Asymmetry Factor ◽

Ice Crystal ◽

Ice Clouds ◽

Submicron Structures ◽

Climate Cooling

Abstract. Ice crystal submicron structures have a large impact on the optical properties of cirrus clouds and consequently on their radiative effect. Although there is growing evidence that atmospheric ice crystals are rarely pristine, direct in-situ observations of the degree of ice crystal complexity are largely missing. Here we show a comprehensive in-situ dataset of ice crystal complexity coupled with measurements of the cloud asymmetry factor collected at diverse geographical locations. Our results demonstrate that an overwhelming fraction (between 61 and 81 %) of atmospheric ice crystals in the different regions sampled contain submicron deformations and, as a consequence, a low asymmetry factor of 0.75 is observed. The measured cloud angular light scattering functions were parameterized in terms of the cloud bulk asymmetry factor and tested in a global climate model. The modelling results suggest that due to ice crystal complexity, ice clouds can induce an additional cooling effect of −1.12 W m−2 on the radiative budget that has not yet been considered.

Download Full-text

Surprising similarities in model and observational aerosol radiative forcing estimates

10.5194/acp-2019-533 ◽

2019 ◽

Cited By ~ 3

Author(s):

Edward Gryspeerdt ◽

Johannes Mülmenstädt ◽

Andrew Gettelman ◽

Florent F. Malavelle ◽

Hugh Morrison ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Liquid Water Path ◽

Ice Clouds ◽

Aerosol Radiative Forcing ◽

Aerosol Forcing ◽

Cloud Properties ◽

The Impact

Abstract. The radiative forcing from aerosols (particularly through their interaction with clouds) remains one of the most uncertain components of the human forcing of the climate. Observation-based studies have typically found a smaller aerosol effective radiative forcing than in model simulations and were given preferential weighting in the IPCC AR5 report. With their own sources of uncertainty, it is not clear that observation-based estimates are more reliable. Understanding the source of the model-observational difference is thus vital to reduce uncertainty in the impact of aerosols on the climate. These reported discrepancies arise from the different decompositions of the aerosol forcing used in model and observational studies. Applying the observational decomposition to global climate model output, the two different lines of evidence are surprisingly similar, with a much better agreement on the magnitude of aerosol impacts on cloud properties. Cloud adjustments remain a significant source of uncertainty, particularly for ice clouds. However, they are consistent with the uncertainty from observation-based methods, with the liquid water path adjustment usually enhancing the Twomey effect by less than 50 %. Depending on different sets of assumptions, this work suggests that model and observation-based estimates could be more equally weighted in future synthesis studies.

Download Full-text