Volcanic impacts on the oceans

global climate

Stratospheric sulfur aerosols spread around the globe by the atmospheric circulation, producing surface cooling by scattering solar radiation back to space. This cooling effect on the ocean surface usually lasts for several years as the lifetime of sulfate aerosols is about 2–3 years.^[1] However, in the subsurface ocean the cooling signal may persist for a longer time and may have impacts on some decadal variabilities, such as the Atlantic meridional overturning circulation (AMOC).^[1][2]

VEI>=5) directly reduce global mean sea surface temperature (SST) by approximately 0.2-0.3 °C,^[1][3] milder than global total surface temperature drop, which is ~0.3 to 0.5 °C,^[4][5][6]

Krakatau’s effect in the heat content can be as long as one-century.^[7][8] Relaxation time of the effects of recent volcanoes is generally shorter than those before the 1950s. For example, the recovery time of ocean heat content of Pinatubo, which caused comparable radiative forcing to Krakatau, seems to be much shorter. This is because Pinatubo happened under a warm and non-stationary background with increasing greenhouse gas forcing.^[7] However, its signal still could penetrate down to ~1000 m deep.^[1]

mean sea level on a decadal time scale.^[2] However, Grinsted [2007] argued that a significant sea level rise is the first direct response to the volcanic eruption, and after that sea level becomes to drop. One possible explanation for this phenomenon is the imbalance of ocean mass fluxes. After a volcanic eruption, evaporation over ocean will lower, because it is largely determined by the ocean surface temperature change. The quick response of evaporation to the surface cooling and the delayed response of river runoff to the associated lower precipitation lead to an increased sea level. About 1~2 years later, river discharge becomes less due to the reduced precipitation and less sea ice melting, which cause sea level to drop.^[10]

Krakatau and Pinatubo.^[1][13]