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Tokano, Tetsuya ORCID: 0000-0002-7518-9245 and Lorenz, Ralph D. (2019). Modeling of Seasonal Lake Level Fluctuations of Titan's Seas/Lakes. J. Geophys. Res.-Planets, 124 (2). S. 617 - 636. WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 2169-9100

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Abstract

Seasonal variations in lake levels of Titan's hydrocarbon seas/lakes are predicted by an ocean circulation model in an effort to understand the observed temporal changes in lake size or lack thereof. Three different ground permeabilities are assumed so as to change the relative importance of precipitation, evaporation, river runoff, and groundwater seepage for the lake methane budget. The lake level generally rises in the rainy season around the summer solstice and falls or stagnates during long dry periods in autumn and winter. The annual lake level range in the northern hemisphere amounts to 50-120cm depending on geographic location and size of the lakes and ground permeability. If the hydraulic connection between Punga Mare and Kraken Mare is weak, the lake level range of Punga Mare amplifies at the expense of other seas and also establishes a large lake level difference between these two seas, which is not compatible with the observation by the Cassini spacecraft. On-lake precipitation would cause the lake level of Ontario Lacus to vary seasonally by merely 15 cm, yet river runoff from the huge catchment area can increase the annual lake level range to several meters. The shrinkage of Ontario Lacus observed by Cassini is more likely to be caused by lakebed seepage than by evaporation. The ultimate cause of the difference in the seasonal behavior between northern and southern lakes may be the hemispheric asymmetry in precipitation, be it caused astronomically or topographically. Plain Language Summary Saturn's moon Titan has many hydrocarbon lakes in the polar region, but only one lake near the south pole has so far shown evidence of lake size change. In order to understand the possible difference in the temporal variation between the northern and southern lakes, we simulated numerically the seasonal lake level change of all major lakes on Titan. The lake level generally rises in spring and summer during the rainy season and falls in dry seasons due to evaporation. However, the magnitude of lake level variation strongly depends on the geographic location and size of the lakes as well as how the ground outside the lakes and lake bottom are made of. Large seas near the north pole experience moderate lake level changes of about 1m as a response to spatially averaged precipitation and evaporation. Ontario Lacus in the southern hemisphere is located in a dry environment and rapidly grows after sporadic rainfall but also rapidly shrinks by leakage from the lake bottom. This difference ultimately reflects the north-south asymmetry in Titan's climate.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Tokano, Tetsuya UNSPECIFIED orcid.org/0000-0002-7518-9245 UNSPECIFIED Lorenz, Ralph D. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-157224
DOI:	10.1029/2018JE005898
Journal or Publication Title:	J. Geophys. Res.-Planets
Volume:	124
Number:	2
Page Range:	S. 617 - 636
Date:	2019
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	2169-9100
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language LIGEIA MARE; BATHYMETRY; LIQUID; CIRCULATION; SIMULATIONS; CYCLE Multiple languages Geochemistry & Geophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/15722