What is standard atmospheric pressure at mean sea level, and what do closely spaced isobars (isobaras) on a SHOA / Servimet synoptic weather chart indicate?

1. 1013.25 hPa (mbar) / 760 mm Hg; closely spaced isobars represent a steep pressure gradient resulting in strong winds
2. 1000.00 hPa; closely spaced isobars indicate light, variable breezes
3. 1050.00 hPa; closely spaced isobars indicate dense fog with zero wind
4. 980.00 hPa; closely spaced isobars mean the ocean current is flowing backward