Article Modelling the Present Global Terrestrial Climatic Response Due to a Chicxulub-Type Impact

Víctor M. Mendoza 1, Blanca Mendoza 2,*, René Garduño 1 and Marni Pazos 1

1 Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de Mexico, Ciudad Universitaria, CDMX 04510, Mexico; [email protected] (V.M.M.); [email protected] (R.G.); [email protected] (M.P.) 2 Escuela Nacional de Ciencias de la Tierra, Universidad Nacional Autónoma de Mexico, Ciudad Universitaria, CDMX 04510, Mexico * Correspondence: [email protected]

 Received: 6 May 2020; Accepted: 10 July 2020; Published: 14 July 2020 

Abstract: A Chicxulub-like asteroid event occurs, on average, approximately every ~27 to 200 million years. Therefore, such an event could happen presently. Here, we simulate the climatic anomalies it may cause with respect to the current conditions, assuming the same target geology of carbonates and evaporates and a 1 Gt release of sulphate gases. We used a thermodynamic model, including water vapor, cloudiness (by greenhouse and albedo effects), and cryosphere feedback to calculate cooling. We found that it took nearly 4.5 years for solar to recover its preimpact value—during the first year practically no solar radiation reached the surface. Recovery of the temperature took more than 45 years. The lowest temperatures occurred between 1.5 and 5 years after the impact, being the coldest at 14 C below the preimpact temperature. July surface temperature − ◦ anomalies occurred 1.5 years after the impact, becoming one of the largest, compared to preimpact temperatures. Most continents showed temperature anomalies of 45 C. The least cold places were − ◦ the polar regions with temperature anomalies between approximately 5 and 0 C. As for the most − ◦ remarkable climatic effect, we found that, for ~6 years, the extended over almost all the ocean surface and, after ~25 years, it covered nearly half of the surface, remaining so for beyond 45 years. The continental ice remained without reduction beyond 45 years. Sixty years after the impact, the surface oceanic and continental fractions covered by ice were 0.52 and 0.98, respectively. We also modeled the effect of smaller quantities of sulfur released after asteroid impacts, concluding that an instantaneous, large climatic perturbation attributed to a loading range may lead to a semi-permanent shift in the climate system.

Keywords: global climate models; sudden ; Chicxulub; asteroid impact; water vapor feedback; albedo-ice feedback; cloud feedback

1. Introduction The impact of large-size (~10 to 15 km in diameter) undoubtedly poses a threat to life on , as it may cause wide reaching environmental consequences, such as [1–4], seismic shakings [5,6], impact-generated fires [7,8], tsunami [8–10], giant sediment gravity flows [11], or water vapor injection into the atmosphere [12]. The impacts of such magnitude occur on average every few ten to hundred million years [13]. One such object struck the Earth around 66.04 million years ago [14], therefore, such an event may happen in the present, although currently there are no large untracked asteroids. This object created a crater of about 12 km in diameter [15,16] in what is now the Yucatán Peninsula in México, known as Chicxulub. It likely caused the of 75% of life on Earth [1–4]. Although

Atmosphere 2020, 11, 747; doi:10.3390/atmos11070747 www.mdpi.com/journal/atmosphere Atmosphere 2020, 11, 747 2 of 11 there is a competing theory concerning the volcanic volatile emissions from the in the Deccan volcanic province in India [17], studies of the effect of CO2 release from the largest Deccan flow show no correlation with the K-Pg extinctions [8,18]. The asteroid impacted on a sulfur-rich area, ejecting sulfur (S)-bearing gases, high speed solid material, dust, and ashes that reached up to the tropopause [8,15,19]. Many studies have shown that, after the heat wave passed, the sulphate drastically diminished the incoming solar radiation at the surface over several months [20–22]. The aim of this paper is to model sudden climate change due to the effect of sulphate aerosols after the impact of a large-size asteroid in present day.

2. The Model In the experiments reported here, we use the Thermodynamic Climate Model (TCM), described in detail in previous works [23,24]. It is an energy balance model consisting of an atmospheric layer of about 11 km thickness, an oceanic mixed layer 60 m in depth and a continental layer of negligible depth. The model also includes a cloud cover, whose horizontal extent is a function of the tropospheric temperature at the 700 mb level (~3.0 km of altitude). This cloud cover is the superposition of low and middle clouds relevant to the climate [25]. It also includes the cryosphere over oceans and continents, with a layer of permanent ice and a seasonal snow-ice layer. The wind horizontal heat transport is calculated using the observed climatology wind. The turbulent transport, due to mid-latitude cyclones and anticyclones, is parametrized by a diffusion austausch coefficient assumed constant. The TCM is integrated over a global grid with a resolution of 1 per side and the poles are not part of the grid. The value at the pole is obtained by using Gauss’ theorem, applied to the thermodynamic differential equation of tropospheric temperature on the geometric cap delimited by the grid ring surrounding each pole. The line integral is evaluated along this grid ring. The model has three sets of feedback due to the respective water phases: vapor (gas), clouds (liquid) and cryosphere (solid). The first feedback is described in [25] and the second and third ones are presented hereafter. Based on thermodynamic definitions and relations [23,26], the model obtains profiles of atmospheric temperature and partial vapor pressure (e). With these functions of height (z), they evaluate the precipitable water (w). This is in turn written in terms of the relative humidity (f ) and semi-empirical linear parametrizations of f in z = 0 as functions of its vertical mean (fm) and the cloudiness (ε)[27]. Using the Clausius–Clapeyron equation, a proportionality is found between the increases (∆) in w and the air surface temperature (Ta) and a negative one between ∆ε and ∆Ta. This negative correlation yields (in general) positive feedback in climate change via the cloud albedo, but when there is no solar radiation, as in large-asteroid impact darkening, the cloud albedo effect is negligible and, instead, its greenhouse effect (usually secondary) becomes important, changing the feedback sign. The snow-ice feedback discussed in [24] is incorporated by the snow accumulation that forms the polar cap, which is determined by the radiative cooling of the atmosphere and surface (as with nightly freezing) due to the stratospheric aerosols. We further consider the ocean and continent heat exchange with the subsurface, a process through which, in successive layers, the internal energy is stored by heat transfer during daylight and released during the long “night”, also produced by the stratospheric aerosols in a process similar to that of the winter night on Mars [24]. The equation of conservation of thermal energy in the is integrated implicitly, expressed as a linear elliptic partial differential equation of second order in the temperature at the mid tropospheric level. At the surface it is expressed as an algebraic equation where the oceanic and continental temperatures are linear functions of the temperature at the mid tropospheric level and the surface albedo. The fundamental variables of the model are the air temperature at the mid tropospheric level and the oceanic and continental surface temperatures. The model first computes the climatological atmosphere Atmosphere 2020, 11, 747 3 of 11 and ocean temperatures using that of the previous month. It also uses observed climatological fields, such as the latent heat, the heat released due to the vapor condensation, the geostrophic zonal, and meridional wind components (calculated with the observed values of temperature and potential height at the 700 mb level). These climatological variables, also named normal, are according to the WMO, 30-year averages of 1961–1990, adopted by the IPCC. We assume that, on such a long-term, all the variables achieve radiative–convective equilibrium. In that equilibrium, the temperature reaches a linear profile with a standard lapse rate of Γ = 6.5 10 3Km 1. × − − After calculating the normal temperature, the model computes the abnormal value obtained incorporating the forcings. The temperature anomaly is found by subtracting the normal temperature from the abnormal one.

The Forcing

In the present work, we use the H2SO4 aerosols as external forcing, that, in turn, produce a radiative forcing by decreasing the incoming light. The decrease in incoming light may progressively lead to a stop in and suppress the trophic chain. In [28] the authors have shown that the atmospheric dust-loading threshold for submicrometer-size dust is 1016 g, in order to shut down photosynthesis. Below this mass, light levels remain sufficient for photosynthesis. Furthermore, in [22] the authors calculated that, if the associated Chicxulub impact dust-loading mass was below 1014 g, then the dust was not the dominant substance in the radiation decrease. Therefore, the aerosols have a relevant role, and those with greater climatic effect are the H2SO4 aerosols, which result from the SO2 and SO3 thrown by the impact. The first oxidizes, increasing the second. The SO3 reacts, in turn, with the tropospheric water and reaches the stratosphere as H2SO4, where it remains for years [29].

3. Results In the performed numerical simulations, we assumed that the preimpact climate was the present climate. The preimpact external forcings are: the CO2 atmospheric concentration of 350.7 ppm, using the Mauna Loa Observatory annual average for the period 1975–2012 [30]; a Total Solar Irradiance (TSI) value of 1360.8 0.5 W/m2, measured by the Total Irradiance Monitor (TIM) on the spaceborne SOlar ± Radiation and Climate Experiment (SORCE) in 2008 [31], which is 4.5 Wm2 lower than the widely ∼ used Physikalisch-Meteorologisches Observatorium Davos (PMOD) TSI composite. The difference is probably due to instrumental biases in measurements prior to TIM. According to [29], the Chicxulub asteroid impact released 100 Gt of S-bearing gases in a proportion of 80% SO2 and 20% SO3. The SO3 reacts rapidly with the H2O, also released by the impact, forming the H2SO4 aerosol. This aerosol remains in the stratosphere, while the aerosols in the troposphere are rapidly washed away. During volcanic eruptions, the formation of sulphates is also activated by SO2 oxidation in SO3. For instance, for the Pinatubo eruption, the oxidation time was ~90 days [32], while for the Chicxulub this time could be between ~7.6 to 209 years, exceeding the residence time of trace gases in the low stratosphere, which is ~2 years. In the atmosphere, the sulphate aerosols heat the stratosphere and cool the troposphere and the surface, due to the absorption of the incident shortwave radiation, causes a strong stratification that extends the residence aerosol time. In [29] the authors calculated the radiative transmission in the visible residence times of 2.1, 4.3, and 10.8 years. In the present work we consider an asteroid impact that released 100 Gt of S-bearing gases in a proportion of 80% SO2 and 20% SO3 [29], a residence aerosol time in the stratosphere of 2.1 years (to obtain the solar radiation that reaches the surface), and finally, we considered that the object strikes at the same angle on the same type of geologic target—a partially submerged platform constituted by a thick sequence (3 km) of carbonates and sulphate evaporites. In Figure1 we show the fraction of the global surface solar radiation (the external forcing), direct plus diffuse and with no clouds, during the impact with respect to its preimpact value. The zero in the time axis corresponds to the moment of the impact. We notice that it takes nearly 4.5 years for the Atmosphere 2020, 11, 747 4 of 11

Atmosphere 2020, 11, x FOR PEER REVIEW 4 of 11 solar radiation to recover its preimpact value. In particular, during the first year, practically no solar radiationyears for reaches the solar the radiation surface. to recover its preimpact value. In particular, during the first year, practically no solar radiation reaches the surface.

FigureFigure 1.1. FractionFraction ofof thethe surfacesurface solarsolar radiationradiation reachingreaching thethe surfacesurface duringduring andand afterafter thethe asteroidasteroid impact.impact. TheThe zerozero inin the the time time axis axis represents represents the the moment moment of of the the impact. impact.

InIn FigureFigure2 2 we we showshow thethe annual global global surface surface temperature temperature during during and and after after the the impact impact.. The Thepreimpact preimpact output output model model temperature, temperature, is 14.8 is °C, 14.8 coinciding,◦C, coinciding, as expected, as expected, with the with present the presentaverage averageglobal temperature. global temperature. We use We three use sets three of setsfeedback: of feedback: water vapor water; vapor;water watervapor vapor and clouds and clouds;; water watervapor, vapor, clouds clouds,, and albedo and albedo,, associated associated with the with icethe cover ice over cover continents over continents and oceans. and oceans. The ice Thecover ice is coverformed is formed due to due theto cooling the cooling produced produced by by stratospheric stratospheric aerosols. aerosols. A Additionally,dditionally, the the cloud cover cover anomalyanomaly isis presented.presented. TheThe modelmodel consideringconsidering onlyonly thethe waterwater vaporvapor producesproduces thethe fastestfastest preimpactpreimpact temperaturetemperature recovery:recovery: ~10~10 yearsyears afterafter thethe impact.impact. AddingAdding thethe clouds,clouds, itit takestakes almostalmost 4545 yearsyears forfor thethe globalglobal temperature temperature to to recover recover the the preimpact preimpact value. value. Finally, Finally considering, considering the the three three sets sets of feedback, of feedback, the recoverythe recovery of the of preimpact the preimpact temperature temperature value value takes takes a time a longertime longer than 45than years, 45 years with, a with stable a valuestable ofvalue3.5 ofC. −3 The.5 °C period. The period of lowest of lowest temperatures temperatures occurs occur betweens between 1.5 and 1.5 5 yearsand 5 and years the and deepest the deepest phase − ◦ isphase reached is reached ~3 years ~3 afteryears the after impact. the impact. The presence The presence of maximum of maximum cloudiness, cloudiness up to, up ~4 to years ~4 years after after the impact,the impact, prevents prevents larger larger cooling cooling due due to its to greenhouse its greenhouse effect; effect; however, however after, after this time,this time, although although the solarthe solar radiation radiation at the at surface the surface has almost has almost reached reached its pre-impact its pre-impact value, asvalue shown, as shown in Figure in1 Figure, the clouds 1, the produceclouds produce an albedo an ealbedoffect that effect keeps that thekeeps surface the surface cool for cool a longerfor a longer time, t whichime, which is the is reason the reason for the for dithefference difference between between the scenariosthe scenarios with with and and without without clouds. clouds. The The model model found found in in [33 [33]] is is also also shown shown inin Figure Figure2 .2. Figure3 shows the ice fraction over the ocean surface during and after the impact. We consider two feedback scenarios: Water vapor and clouds; water vapor, clouds, and ice cap albedo, formed due to the impact. Considering the first one, the ice covers almost all the ocean surface ~5 years after the impact and its reduction to preimpact values takes around 20 years. Taking the water vapor, clouds and albedo into consideration, for ~6 years the ice covers almost all the ocean surface and after ~25 years such an ice layer is reduced to nearly half of the sea surface, remaining very stable beyond 45 years. The model of [33] is also shown.

Atmosphere 2020, 11, x FOR PEER REVIEW 5 of 11

Atmosphere 2020, 11, 747 5 of 11

Atmosphere 2020, 11, x FOR PEER REVIEW 5 of 11

Figure 2. Annual global surface temperature during and after the impact. Three sets of feedback are used: water vapor (short-dashed curve); water vapor and clouds (long-dashed curve); water vapor, clouds, and ice albedo (solid curve). The modeled fractional cloud cover anomaly is the dotted curve. The simulation in [33], including these three types of feedback, is the dashed–dotted curve.

Figure 3 shows the ice fraction over the ocean surface during and after the impact. We consider two feedback scenarios: Water vapor and clouds; water vapor, clouds, and ice cap albedo, formed due to the impact. Considering the first one, the ice covers almost all the ocean surface ~5 years after theFigure impactFigure 2. 2. Annualand Annual its globalreduction global surface surface to temperature preimpacttemperature duringvalues during andtakes and after after around the the impact. impact. 20 years. Three Three Taking sets sets of of feedback thefeedback water are are vapor, cloudsused:used: and water water albedo vapor vapor into (short-dashed (short consideration-dashed curve); curve), for water; water ~6 vaporyears vapor andthe and cloudsice clouds covers (long-dashed (long almost-dashed all curve); curve) the ocean water; water vapor,surface vapor, and afterclouds,clouds ~25 years and, and ice icesuch albedo albedo an (solidice (solid layer curve). curve). is reduced The The modeled modeled to nearly fractional fractional half cloud cloud of the cover cover sea anomaly anomalysurface, is isremaining the the dotted dottedcurve. verycurve. stable beyondTheThe simulation 45simulation years. inThe in [33 [33 model],] including, including of [33 these these] is threealso three shown. types types of of feedback, feedback is, is the the dashed–dotted dashed–dotted curve. curve.

Figure 3 shows the ice fraction over the ocean surface during and after the impact. We consider two feedback scenarios: Water vapor and clouds; water vapor, clouds, and ice cap albedo, formed due to the impact. Considering the first one, the ice covers almost all the ocean surface ~5 years after the impact and its reduction to preimpact values takes around 20 years. Taking the water vapor, clouds and albedo into consideration, for ~6 years the ice covers almost all the ocean surface and after ~25 years such an ice layer is reduced to nearly half of the sea surface, remaining very stable beyond 45 years. The model of [33] is also shown.

FigureFigure 3. 3.Ice Ice surface surface fraction fraction over over the the oceans oceans during during and and after after the the impact. impact. Calculated Calculated using using water water vaporvapor and and cloud cloud feedback feedback (short-dashed (short-dashed curve) curve) and and adding adding the the ice ice albedoalbedo (solid(solid curve).curve). The result in in[33 [33]] is is the the dashed dashed–dotted–dotted curve.

Figure4 presents the ice fraction over the continental surface during and after the impact. We considered again two scenarios: water vapor and clouds; water vapor, clouds, and the ice cap albedo. If we consider the first scenario, the ice almost covers all the continental surface for 7 years after the impact, and after ~25 years it reduces to nearly 40% of its preimpact values remaining so for a longerFigure time. 3. If weIce surface take the fraction water over vapor, the clouds oceans andduring albedo, and after the icethe almostimpact. coversCalculated all theusing continental water surfacevapor without and cloud reduction feedback beyond (short 45-dashed years. curve) and adding the ice albedo (solid curve). The result in [33] is the dashed–dotted curve.

Atmosphere 2020, 11, x FOR PEER REVIEW 6 of 11 Atmosphere 2020, 11, x FOR PEER REVIEW 6 of 11 Figure 4 presents the ice fraction over the continental surface during and after the impact. We consideredFigure 4 againpresents two the scenarios: ice fraction water over vapor the continental and clouds surface; water during vapor, and clouds after, andthe impact. the ice We cap consideredalbedo. If we again consider two scenarios:the first scenario water , vaporthe ice and almost clouds covers; water all the vapor, continental clouds ,surface and the for ice 7 years cap albedo.after the If impact,we consider and after the first~25 yearsscenario it reduces, the ice to almost nearly covers 40% of all its the preim continentalpact values surface remaining for 7 years so for aftera longer the impact, time. If andwe takeafter the ~25 water years vapor, it reduces clouds to nearly and albedo, 40% of the its icepreim almostpact covers values all remaining the continental so for asurface longer withouttime. If we reduction take the beyond water vapor, 45 years. clouds and albedo, the ice almost covers all the continental Atmospheresurface without2020, 11, 747reduction beyond 45 years. 6 of 11

Figure 4. Ice surface fraction over the continents during and after the impact. Calculated using water Figurevapor 4.and Ice cloud surface feedback fraction (short over – thedashed continents curve) during and adding and after the ice the albedo impact.impact (solid. Calculated curve). using water vapor and cloud feedback (short–dashed(short–dashed curve)curve) andand addingadding thethe iceice albedoalbedo (solid(solid curve).curve). Usually, in climate change simulations, the largest anomalies (either positive or negative) are obtainedUsually, in J ininuly. climateclimate Figure changechange 5 shows simulations,simulations, the temperature the largest anomaly anomalies in July (either over the positive ocean or and negative) continental are obtainedsurfaces in due July.July. to theFigure stratospheric 55 showsshows thethe sulphate temperaturetemperature aerosols anomalyanomaly 1.5 years inin July July after overover the the theimpact, oceanocean one andand of continentalcontinental the coldest surfacestimes, according due due to to the the to stratospheric stratospheric Figure 2. The sulphate sulphate three aerosolssets aerosols of feedback 1.5 1.5 years years after are after included. the impact, the impact, Almost one of one all the theof coldest thecontinents, coldest times, accordingtimesexcept, according Sout to Figureh America to2 . Figure The and three 2. Oceania, The sets threeof feedback are sets the of coldest are feedback included. places are, Almost presenting included. all the Almost a continents, temperature all the except continents, anomaly South of Americaexceptaround Sout −4 and5h °C. Oceania, America The less are and cold the Oceania, places coldest are are places, the the polar coldestpresenting regions places, awith temperature, presenting temperature anomaly a temperatureanomalies of around between anomaly45 −5 ofC.°C − ◦ Thearoundand less 0 °C. −4 cold 5 °C. places The less are thecold polar places regions, are the with polar temperature regions, with anomalies temperature between anomalies5 C andbetween 0 C. −5 °C − ◦ ◦ and 0 °C.

FigureFigure 5. 5. JulyJuly surface surface temperaturetemperature anomaly anomaly 1.5 1.5 years years after after the the impact, impact, one one of of the the coldest coldest times. times. CalculatedFigureCalculated 5. July using using surface water water vapor,temperature vapor, clouds, clouds anomaly and, and ice ice albedo 1.5albedo years feedback. feedback. after the impact, one of the coldest times. Calculated using water vapor, clouds, and ice albedo feedback. Figure6 presents the surface continental and oceanic ice cap anomaly 60 years after the impact.

The fraction of oceans covered by ice is 0.52, as shown in Figure3, and the fraction of the continents covered by ice is 0.98, as shown in Figure4. In the polar regions, after the impact no significant ice was added because they are very dry. This simulation incorporates water vapor, clouds, and ice albedo feedback. Atmosphere 2020, 11, x FOR PEER REVIEW 7 of 11

Figure 6 presents the surface continental and oceanic ice cap anomaly 60 years after the impact. The fraction of oceans covered by ice is 0.52, as shown in Figure 3, and the fraction of the continents covered by ice is 0.98, as shown in Figure 4. In the polar regions, after the impact no significant ice Atmospherewas added2020 because, 11, 747 they are very dry. This simulation incorporates water vapor, clouds, and7 of ice 11 albedo feedback.

FigureFigure 6.6. ContinentalContinental andand oceanicoceanic iceice capcap anomalyanomaly 6060 yearsyears afterafter thethe impactimpact calculatedcalculated usingusing waterwater vapor,vapor, cloud,cloud, andand iceice albedoalbedo feedback.feedback. ColorColor code:code: regions with ice thickness of more thanthan 11 m,m, fromfrom graygray (thinner(thinner ice ice cap) cap) to to white white (thicker (thicker ice ice cap); cap); regions regions with with no ice no or ice ice or thickness ice thickness less than less1 than m, black. 1 m, 4. Discussionblack.

4. DiscussionIn this section we compare our results with those in [33], who used a conservative estimate of 100 Gt of S-bearing gases, and included in their simulations the water vapor, cloud, and ice albedo In this section we compare our results with those in [33], who used a conservative estimate of feedback. In the modern scenario we use the same low estimate of 100 Gt of S-atmospheric loading after 100 Gt of S-bearing gases, and included in their simulations the water vapor, cloud, and ice albedo the impact. Additionally, they used a preimpact value of 18.9 ◦C, corresponding to the temperature feedback. In the modern scenario we use the same low estimate of 100 Gt of S-atmospheric loading at the end of the Cretaceous, higher than the 14.8 ◦C found here. They used a CO2 atmospheric after the impact. Additionally, they used a preimpact value of 18.9 °C , corresponding to the2 concentration of 500 ppm—in our model we used 350.7 ppm. Moreover, they used a TSI of 1354 Wm− , temperature at the end of the Cretaceous, higher than2 the 14.8 °C found here. They used a CO2 and in this paper we use a higher value of 1360.8 Wm− . atmospheric concentration of 500 ppm—in our model we used 350.7 ppm. Moreover, they used a TSI The annual global temperature found in [33] is shown in Figure2. The maximum cooling was of 1354 Wm−2, and in this paper we use a higher value of 1360.8 Wm−2. 7.5 ◦C, while our simulation reaches a lower value of 13.5 ◦C. Nevertheless the changes with respect − The annual global temperature found in [33] is shown− in Figure 2. The maximum cooling was to the climatic value are not that different—in [33] it is 26.4 C (it goes from 18.9 to 7.5 C) and in −7.5 °C, while our simulation reaches a lower value of −1◦3.5 °C. Nevertheless the− changes◦ with our case it is 28.3 ◦C (it goes from 14.8 to 13.5 ◦C). The temperature in [33] approached its preimpact respect to the climatic value are not that− different—in [33] it is 26.4 °C (it goes from 18.9 to −7.5 °C) value after 30 years, whereas in our model the case closest to this behavior is the one including only and in our case it is 28.3 °C (it goes from 14.8 to −13.5 °C). The temperature in [33] approached its the water vapor feedback. The lowest temperature in both [33] and our model occurs ~3 years after the preimpact value after 30 years, whereas in our model the case closest to this behavior is the one impact. In [33], they found that the sea ice surface reached its maximum thickness fraction of ~0.15 including only the water vapor feedback. The lowest temperature in both [33] and our model occurs approximately 4 years after impact, and ~20 years after impact it almost achieved preimpact values. 3 years after the impact. In [33], they found that the sea ice surface reached its maximum thickness Our model, considering the water vapor and cloud feedback, and the simulation in [33], coincides in fraction of ~0.15 approximately 4 years after impact, and ~20 years after impact it almost achieved that the ice sea surface fraction almost reaches its preimpact values after 20 years. preimpact values. Our model, considering the water vapor and cloud feedback, and the simulation As far as we can see, the difference between our results and those in [33] may be attributed to in [33], coincides in that the ice sea surface fraction almost reaches its preimpact values after 20 the following effects: the different preimpact temperatures used; the larger greenhouse effect in [33]; years. an increase of 149.3 ppm in CO (the difference between the models’ CO concentrations) can further As far as we can see, the difference2 between our results and those2 in [33] may be attributed to increase the temperature ~2 C and such an effect remains even in the nearly complete absence of the following effects: the different◦ preimpact temperatures used; the larger in [33]; solar radiation; the different TSI values, our value is ~0.5% higher than that in [32], which implies an an increase of 149.3 ppm in CO2 (the difference between the models’ CO2 concentrations) can further increased temperature of 0.5 C. Summarizing, the model in [33] has a higher preimpact temperature increase the temperature ~2 ◦°C and such an effect remains even in the nearly complete absence of than our model. Furthermore, the sea ice model (dynamic–thermodynamic) is used in [33], but in our solar radiation; the different TSI values, our value is ~0.5% higher than that in [32], which implies an model, the sea ice mass per unit area and time is proportional to the difference between the latent heat increased temperature of 0.5 °C. Summarizing, the model in [33] has a higher preimpact temperature released by vapor condensation, and the latent heat that is yielded by vaporization or sublimation than our model. Furthermore, the sea ice model (dynamic–thermodynamic) is used in [33], but in from the surface. In [33], the surface cooling provoked a vigorous ocean mixing, where the resurgence of less cold water prevented the surface ice accumulation. In our model, the sea ice surface is formed by thermodynamic processes. During the period of low solar radiation there was a constant ice surface Atmosphere 2020, 11, x FOR PEER REVIEW 8 of 11 our model, the sea ice mass per unit area and time is proportional to the difference between the latent heat released by vapor condensation, and the latent heat that is yielded by vaporization or sublimationAtmosphere 2020 from, 11, 747 the surface. In [33], the surface cooling provoked a vigorous ocean mixing, where8 of 11 the resurgence of less cold water prevented the surface ice accumulation. In our model, the sea ice surface is formed by thermodynamic processes. During the period of low solar radiation there was a constantaccumulation. ice surface When accumulation the solar radiation. When achieved the solar its radiation preimpact achieved value, the its ice preimpact albedo feedback value, the had ic ane albedoimportant feedback roll in had maintaining an important the icerol capsl in maintaining for a long time. the ice caps for a long time. FurtherFurthermore,more, after after the asteroid impact, wewe modelledmodelled thethee effectffect of of releasing releasing di differentfferent quantities quantities of ofsulphate sulphate gases gases in ain proportion a proportion of 80% of 80% SO2 SOand2 and 20% 2 SO0%3. SO We3. usedWe use waterd water vapor, vapor, clouds, clouds and ice, and albedo ice albedofeedback. feedback We considered. We consider the impactsed the impacts of loading of loading the atmosphere the atmosphere with 1, 5, with and 1, 100 5, Gtand of 100 S-bearing Gt of Sgases.-bearing Asteroids gases. Asteroids that impact that the impact Earth the can Earth inject can large inject S quantities large S quantiti into thees into stratosphere. the stratosphere. In [34] theIn [34authors] the aut calculatedhors calculated the S abundances the S abundances of carbonaceous of carbonaceous asteroids asteroids with diameters with diameters between 0.1 between and 10 0.1 km. andThey 10 found km. They that 0.15found km that asteroids 0.15 km contain asteroids as much contain S asas the much entire S as modern the entire stratosphere modern stratosphere and that the andS in that a 10 the km S asteroid in a 10 iskm nearly asteroid six ordersis nearly of magnitudesix orders of larger. magnitude Moreover, larger. in [Moreover,29] the authors in [29] found the authorsthat, for found a loading that larger, for a thanloading 25 Gt, larger the magnitudethan 25 Gt and, the duration magnitude of the and maximum duration radiativeof the maximum forcing is radiativeindependent forcing of the is independent initial gas release. of the Followinginitial gas release. [29], we Following assume that [29], the we released assume material that the between released 1 materand 5ial Gt between comes only 1 and from 5 Gt the comes asteroid only and from not the from asteroid the impact and not place, from while the theimpact 100 Gtplace, comes while mainly the 100from Gt the comes target. mainly We use from the the climate target. forcing We use model the climate results, forcing developed model in [results29], to, calculatedeveloped the in radiative [29], to calculateforcing. Figurethe radiative7 shows forcing. the annual Figure global 7 shows surface the temperature. annual glo Webal noticed surface that temperature the smaller. W thee notice loadingd thatthe higherthe smaller the temperature the loading minimum—aroundthe higher the temperature14, 10, minimum and 2 —Caround for 100, −1 5 and4, −1 10 Gt,, and respectively. −2 °C for − − − ◦ 100,After 5 ~25and y,1 theGt, 1respectively. and 5 Gt temperatures After ~25 reachy, the also1 and a nearly 5 Gt temperatures constant value reach of ~1 also◦C, compareda nearly constant with the value100 Gt, of which ~1 °C, keepscompared the temperature with the 100 close Gt, towhich3.5 keepsC. However, the temperature in the three close cases, to −3 the.5 low°C. However, temperatures in − ◦ thego beyondthree cases 45, y the after low the temperatures impact; therefore, go beyond a semi-permanent 45 y after the shiftimpact of; climatetherefore seems, a semi to- bepermanent achieved. shiftFigure of 8climate shows seems the ice to surface be achieved. fraction Figure over the8 shows oceans. the Again,ice surface the smallerfraction theover loading, the oceans the. smallerAgain, thethe smaller ice fraction the over loading the, ocean.the smaller The maximum the ice fraction ice coverage over the occurs ocean within. The themaximum first 5 years ice coverage after the occursimpact—almost within the allfirst the 5 years ocean after surface, the impact ~0.85%— andalmost ~0.35% all the for ocean 100, surface, 5 and 1 ~0.85% Gt, respectively. and ~0.35% After for 100,~25 years,5 and such1 Gt, anrespectively ice layer is. A reducedfter ~25 to years nearly, such half an of ice the layer sea surface, is reduced and ~0.20%to nearly of half the seaof the surface sea surface,for 100, and and ~0.20% both 5 of and the 1 sea Gt, surface respectively. for 100, The and ice both fraction 5 and for 1 Gt, the respectively. three cases remainsThe ice fraction very stable for thebeyond three 45 cases years. remains Again, very this stable suggests beyond a semi-permanent 45 years. Again shift, this of climate.suggests In a [semi29], the-permanent authors modeled shift of climate.the climate In [29] forcing, the authors for S-loadings modeled between the climate 1 to 300 forcing Gt, and for forS-loadings the Pitanubo between as a 1 loading to 300 Gt, lower and limit. for theThey Pitanubo found thatas a loading the radiative lower forcing limit. They associated found that with the Pitanubo radiative is aroundforcing associated two orders with of magnitude Pitanubo islower around than two that orders associated of magnitude to the 1 Gt lower loading. than Its that climatic associated effect onlyto the lasted 1 Gt loading for about. I 2tsyears; climatic therefore, effect onlyno long-term lasted for shift about in 2 the years climate; therefore system, no occurred. long-term shift in the climate system occurred.

FigureFigure 7. 7. AnnualAnnual global global surface surface temperature temperature during and after variousvarious asteroidasteroid impacts.impacts. AtmosphericAtmospheric S Sloading loading of: of: 1 1 Gt Gt (pointed (pointed curve), curve), 5 5 Gt Gt (dashed (dashed curve), curve), and and 100 100 Gt Gt (solid (solid curve). curve).

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FigureFigure 8. 8.Ice Ice surface surface fraction fraction over over the the oceans oceans during during and and after after various various asteroid asteroid impacts. impact Atmospherics. Atmospheric S loadingS loading of: of: 1 Gt 1 Gt (pointed (pointed curve), curve), 5 Gt 5 Gt (dashed (dashed curve), curve), and and 100 100 Gt Gt (solid (solid curve). curve).

AsAs indicated indicated above, above, we we assume assume that that the the present present day day asteroid asteroid and and the the Chicxulub-type Chicxulub-typeobject object impactedimpacted in in similar similar places—a places—a partially partially submerged submerged platform platform constitutingconstituting a a thick thick sequence sequence (3 (3 km) km) of of carbonatescarbonates and and sulphate sulphate evaporites. evaporites. Nevertheless, Nevertheless there, there are are other other sulphate sulphate evaporite-rich evaporite-rich provinces provinces in thein world,the world such, such as Solikamsk as Solikamsk in the in Urals the Urals in Russia, in Russia, Soligorsk Soligorsk in Bielorusia, in Bielorusia, Saskatchewan Saskatchewan and New and BrunswickNew Brunswick in Canada, in Canada or Stassfurt, or and Stassfurt Hannover and in Hannover Germany. in In Germany. Spain, they In are Spain in Suria-Cardona,, they are in CabezSuriaó-Cardona,n de la Sal, Cabezón and, in general, de la Sal, in marine and, in basins, general such, in as marine the Guadalquivir basins, such depression. as the Guadalquivir In all these places,depression. a Chicxulub-like In all these impactplaces, a would Chicxulub probably-like produceimpact would a similar probably climatic produce effect. a However, similar climatic if the asteroideffect. However, hits a granite if thecraton—for asteroid hits instance a granite North craton America,—for instance Africa, North or northern America, Asia—the Africa, or sulphate northern loadingAsia—the would sulphate come only loading from would the asteroid, come only represented from the in Figures asteroid,7 and represented8. Moreover, in Figures if the impact 7 and is 8. onMoreover, the oceans, if the and impact if the oceanic is on the crust oceans, does notand haveif the sulphate oceanic evaporitecrust does sediments, not have thesulphate loading evaporite would besediments, mainly water the loading vapor. would In this be case, mainly most water water vapor. vapor In would this case be in, most the troposphere,water vapor would and the be vapor in the introposphere, the stratosphere and the would vapor contribute in the stratosphere to the aerosol would formation contribute of Sto acid, the aerosol as the S formation loading would of S acid, be dueas the only S loading to the asteroid, would be again, due only shown to the in Figures asteroid,7 and again8, which, shown represent in Figures the 7 climaticand 8, which e ffect. represent If the evaporitesthe climatic are effect. mainly If the constituted evaporites by are minerals mainly otherconstituted than sulphates,by minerals then other we than also sulphates, considerthat then the we sulphatesalso consider come that from the the sulphates asteroid. come from the asteroid.

5.5. ConclusionsConclusions AA large-size large-size asteroid asteroid event event on on our our planet planet occurs, occurs on, average, on average every, every ten to ten hundred to hundred million million years. Oneyears of. thoseOne of objects those objects struck thestruck Earth the around Earth around 66.04 million 66.04 million years ago.years Therefore, ago. Therefore such, an such event an event may happenmay happen in the in present. the present. Here, weHere simulated, we simulate the associatedd the associated sudden sudden climate climate change, change with respect, with respect to the present,to the present, of a Chicxulub-like of a Chicxulub asteroid-like asteroid impacting impacting a similar a sulfur-rich similar sulfur target.-rich For target. this purpose For this we purpose used awe thermodynamic used a thermodynamic climate model climate that includes model that the feedback includes caused the feedback by water caused vapor, by cloudiness water vapor, (by greenhousecloudiness and(by albedogreenhouse effects), and and albedo cryosphere, effects), to and calculate cryosphere, global to cooling calculate due global to aerosols cooling produced due to byaerosols the asteroid produced impact by onthe the asteroid Earth. impact We found on the that: Earth. We found that: ItIt takes takes nearly nearly 4.5 4. years5 years for for the the solar solar radiation radiation reaching reaching the surface the surface to recover to recover its preimpact its preimpact value. Invalue particular,. In pa duringrticular, the during first year the practically first year no practically solar radiation no solar reaches radiation the surface. reaches The the recovery surface. of the The preimpactrecovery of temperature the preimpact takes temperature beyond 45 years.takes beyond The coldest 45 years. temperatures The coldest are foundtemperatures between are 1.5 found and 5 years after the impact and the lowest is around 14 C below the preimpact temperature. The July between 1.5 and 5 years after the impact and −the lowest◦ is around −14 °C below the preimpact surfacetemperature. oceanic The and July continental surface temperature oceanic and anomalies, continental 1.5 temperature years after the anomalies, impact, become 1.5 years one after of the the coldest,impact,compared become one to preimpactof the coldest temperatures., compared to Almost preimpact all the temperatures. continents, except Almost South all the America continents, and Oceania, have temperature anomalies of 45 C. The polar regions show lower temperature anomalies, except South America and Oceania, have− temperature◦ anomalies of −45 °C . The polar regions show between 5 and 0 C. lower temperature− ◦ anomalies, between −5 and 0 °C. Our most remarkable results are: For ~6 years the ice extends over almost all the ocean surface, and after ~25 years it covers nearly half of the surface, remaining so beyond 45 years. The continental ice remains without reduction beyond 45 years. Sixty years after the impact, the oceanic surface

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Our most remarkable results are: For ~6 years the ice extends over almost all the ocean surface, and after ~25 years it covers nearly half of the surface, remaining so beyond 45 years. The continental ice remains without reduction beyond 45 years. Sixty years after the impact, the oceanic surface fraction covered by ice is 0.52 and the continental fraction is 0.98. We also modeled the effect of smaller quantities of sulphur released after asteroid impacts, concluding that an instantaneous, large climatic perturbation, attributed to a loading range, can lead to a semi-permanent shift in the climate system.

Author Contributions: Conceptualization, V.M.M. and R.G.; methodology, B.M.; software, M.P. and V.M.M.; validation, B.M. and R.G.; formal analysis, V.M.M.; investigation, B.M.; data curation, V.M.M. and M.P.; writing—original draft preparation, B.M.; writing—review and editing, B.M. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Acknowledgments: We would like to acknowledge Alejandro Aguilar for the help in preparing the figures. Conflicts of Interest: The authors declare no conflict of interest.

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