Glacier's water redistribution changes melting depth, affecting on seafloor spreading rate

Abyssal hill is the most-common geomorphological feature on the ocean floor. There have been several models suggested to explain its formation. Detachment fault and magmatic activity anomaly are known as the mechanism of formation of abyssal hill. Glacial water redistribution is one of hypothesis. Crowly et al tried to reveal relationship between glaciation and magmatic flux under ridge. They assumed that magmatic response to changes in sea level formed abyssal hill, and an increase of magma production caused wider partially molten zone beneath seafloor.

In deglaciation region, because of mantle decompression, an increase of magma production is expected. Crowly et al made a model about glacial water redistribution’s influence on ridge’s magma generation. Crowly et al used Pilo-Pleistocene sea-level as a forcing function of their model and studied Australian-Antarctic ridge region. Their results suggested that abyssal hills record the change of magmatic flux under ridge.

Their model obtained magmatic flux through function of the depth and width of partial molten region, time scale and fluctuation scale of glacial water redistribution, and density difference between water and mantle.

Glacial water redistribution was previously suggested by Huybers et al, however Crowly et al obtained results which contradicts earlier research. In their model, the mass flux is proportional to the width of the partially molten region, contrary to earlier models that variations in crustal thickness are inversely proportional to spreading rate.

In most case, Main driving force of seafloor spreading is the gravity of falling slab. So in my opinion, increase of magmatic flux would thicken oceanic crust, rather accelerating seafloor spreading rate. However, in the ocean with both end is passive margin, the magmatic flux may dominantly control spreading rate. Therefore, I think Crowly et al‘s model from this research seems more logical, however, it depends on type of ridge which model to apply on.

Also, high spreading rate accelerates the subduction of older oceanic plate, which makes average age of oceanic crust. Younger oceanic plate has thicker thickness. Therefore higher spreading rate rises sea surface, Ridge’s distance from center of the earth would regular. So the rise of sea surface acts as thicker ocean over ridge. This would be a negative feedback between magma production and sea surface. The effect of this feedback should be considered together.

It would be better with accurate relation between sea-level shift and magmatic process under ridge. However, this work gives insight on ridge’s magmatic process and pressure over ridge, [김3] and on the Earth systemic relationship between cryosphere and geosphere.

Figure [if supportFields]> SEQ Figure \* ARABIC <![endif]1[if supportFields]><![endif]. Bathymetry at the Australian-Antarctic Ridge compared with the result of this model. They shows highly related topography and power density frequency trend.