Editors' Choice

Science  10 Dec 1999:
Vol. 286, Issue 5447, pp. 2042
  1. Martian Seashores

    Previous studies have suggested that early Mars experienced a warmer and wetter climate, and that liquid water may have been abundant. Head et al. (p. 2134) have analyzed Mars Global Surveyor altimeter data to refine the detailed topography of the martian surface and present evidence that a large ocean existed in the northern lowlands. Their analysis suggests a possible shoreline with smooth topography within the shoreline boundaries, the termination of six outflow channels at the elevation of the shoreline, and the presence of several terraces that may be related to shoreline recession. The estimated volume of water that would have filled this proposed ocean is consistent with estimates of Mars' water budget.

  2. El Niño and CO2

    During El Niño events, the tongue of warm surface water that spreads eastward across the equatorial Pacific Ocean reduces upwelling of cold, carbon dioxide (CO2)-rich water and thus reduces the amount of CO2 that is transferred to the atmosphere. Conversely, during La Niña years, when the eastern equatorial Pacific contains colder-than-average surface water, the CO2 flux from atmosphere to the ocean is high. Chavez et al. (p. 2126; see the cover) have collected data from sea surface sensors, ships, and satellites to construct a detailed picture of the chemistry and biology of the 1997–1998 El Niño, one of the strongest ever observed. These data have allowed them to quantify the effects of zonal winds and ocean circulation on primary productivity and air-sea CO2 fluxes.

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