  The influence of atmospheric composition on the climates of present-day and
early Earth has been studied extensively, but the role of ocean composition has
received less attention. We use the ROCKE-3D ocean-atmosphere general
circulation model to investigate the response of Earth's present-day and
Archean climate system to low vs. high ocean salinity. We find that saltier
oceans yield warmer climates in large part due to changes in ocean dynamics.
Increasing ocean salinity from 20 g/kg to 50 g/kg results in a 71% reduction in
sea ice cover in our present-day Earth scenario. This same salinity change also
halves the pCO$_2$ threshold at which Snowball glaciation occurs in our Archean
scenarios. In combination with higher levels of greenhouse gases such as CO$_2$
and CH$_4$, a saltier ocean may allow for a warm Archean Earth with only
seasonal ice at the poles despite receiving 20% less energy from the Sun.
