Model results: Control run

Temperature:

For the control run GENESIS predicts a global MAT (Mean Annual Temperature) of 20.66°C for model years 15 through 25, almost 6°C higher than the present day MAT of 15°C. Average temperatures around the north pole are slightly below freezing during the coldest months of the northern hemisphere winter (DJF = Dec., Jan., Feb.) (Figure 34). These temperatures correspond very well with those indicated by high-latitude floras (HERMANN and SPICER, 1996, 1997). During the austral winter (northern hemisphere summer) temperatures over Antarctica cool to an average of -12°C. The warmest temperatures occur between 30° north and south over the large continental interiors of Asia, Africa, and South America. During their hemispheric summers (Figure 34 and 35), temperatures in these regions reach more than 35°C. Over the ocean, the temperature is generally

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equal to that of the sea surface, so that tropical sea surface temperatures during NH winter were as high as 32°C (present day: 28°C- max. 30°C). The highest temperatures were reached off the eastern coast of S-America and Africa.

Figure 34: Temperature for Dec., Jan., Feb.; [°C].

Figure 35: Temperature for Jun., Jul., Aug.; [°C].

Precipitation:

The precipitation pattern for this run shows relatively low precipitation for the regions north and south of 75° during northern hemisphere (NH) winter (Figure 36) and NH summer (Figure 37).

Precipitation in these regions does not exceed 2 mm/day. The larger continental interiors of Asia, Africa, and South America are also zones of low precipitation with values of about 0-1 mm/day.

They lie in desert latitudes. Highest precipitation occurs along the equator (up to 12 mm/day) and between 15° north and south, with values ranging from 4-7 mm/day. Another important feature is the establishment of zones of high precipitation between 30° and 60° north and south during their hemispheric winters. These zones weaken during their hemispheric summers. An explanation will be given in the “Atmospheric pressure systems” section below.

Figure 36: Precipitation for Dec., Jan., Feb.; [mm/day].

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Figure 37: Precipitation for Jun., Jul., Aug.; [mm/day].

Atmospheric pressure system:

The air pressure systems for the Late Cenomanian-Early Turonian are strikingly different from those of today, shown in Figure 38 and 39, with polar lows (990-1005 hPa) during the hemispheric winters and relatively low pressure (1009-1016 hPa) during the summers. In the Arctic a very low pressure system forms during NH winter. Strong latitudinal high pressure zones develop around 30° north during boreal winter and 30° south during austral winter. Air Pressure in these zones is usually above 1020 hPa.

For better comparison, the present day pressure system is shown in Figure 40.

Wind systems:

The simulated wind systems shown in Figure 38 and 39 are also different from those of today, too.

Due to the absence of polar highs during the winter, strong westerly wind belts develop between 50° and the high pressure zones at 30°. Changes for the southern hemisphere are similar;.

Another important difference lies in the strong trade winds, which developed during each hemispheric winter.

Figure 38: Wind speed and pressure at sea-level for Dec., Jan., Feb.; [m/s and hPa].

Figure 39: Wind speed and pressure at sea-level for Jun., Jul., Aug.; [m/s and hPa].

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Figure 40: Present day wind speed (surface winds) and pressure at sea-level; [m/s and hPa].

Runoff:

For this study to runoff parameter have been analyzed, surface runoff (surface runoff rate;

mm/day) and subsurface runoff (subsurface drainage rate; mm/day). Surface runoff is defined as the runoff (water) that travels over the soil surface to the nearest surface stream or as runoff of a drainage basin that has not passed beneath the surface since precipitation. However, subsurface runoff is defined as he runoff (water) infiltrating the surface soil and moving toward streams as ephemeral shallow perched ground water above the main ground-water level. It is usually considered part of direct runoff (LANGBEIN & ISERI, 1960).

Surface runoff from land:

Global surface runoff patterns for DJF (Figure 41) and JJA (Figure 42), as simulated by Genesis, predict that the highest surface runoff occurs north of ~40°N and south of ~40°S.

Figure 41: Surface runoff for Dec., Jan., Feb.; [mm/day].

During NH winter (Figure 41) maximum surface runoff occurs over Asia (max. 1.5 mm/day) and over eastern Antarctica (~ 2 mm/day). Notable surface runoff is limited to regions north of 30°N and south of 70°S. Australia, S-Asia, S-America, and Africa have no surface runoff (max. 0.005 mm/day).

Figure 42: Surface runoff for Jun., Jul., Aug.; [mm/day].

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The same picture emerges from surface runoff data for NH summer (Figure 42). Maximum runoff is predicted for eastern Antarctica, central WNA, northern WNA, and Asia. Globally, maximum is simulated off central WNA (Sevier Highlands) and reaches up to 7-9 mm/day.

The eastern craton of N-America, proto-Europe, central and southern Asia, S-America, and Africa do not show any notable surface runoff. Most of these regions do not have any surface runoff at all.

Subsurface runoff (Drainage):

Analysis of seasonal (DJF and JJA) subsurface runoff is shown in Figures 43 and 44. Subsurface runoff is called drainage in GENESIS. It is specified as the amount of water (mm/day) which gets infiltrated into the groundwater system. Groundwater is eventually returned through rivers. Its residence time is usually in the order of 5,000 years (PINNEKER, 1980).

The seasonal data do not show any significant changes in subsurface runoff, except at the southern tip of Asia where a decrease from ~15 mm/day to ~10 mm/day takes place between NH winter and summer. For the rest of the Cretaceous world, subsurface runoff remains almost the same. As already shown in the seasonal precipitation data, the regions where the formation of deserts took place can be distinguished. The subsurface runoff pattern is strongly correlated to precipitation. The simulations suggest desert-like conditions for central S-America, central Africa, south-central-Asia, and on Antarctica. The highest subsurface runoff was simulated for the N-American craton, Greenland, and Europe. Values are between 1.5-2.5 mm/day and slightly higher during the winter. The data for WNA do not show any significant variation throughout the year.

Values generally shift around 1.5-2.5 mm/day.

Figure 43: Subsurface runoff for Dec., Jan., Feb.; [mm/day].

Figure 44: Surface runoff for Jun., Jul., Aug.; [mm/day].