InterRidge 2022 Webinar Series – Evidences from geophysical data for active upwelling and episodic accretion along the slowest spreading Gakkel Ridge

The InterRidge office has invited Dr. Tao Zhang (Senior Scientist, Second Institute of Oceanography) for this month’s webinar. His talk will be about “Evidences from geophysical data for active upwelling and episodic accretion along the slowest spreading Gakkel Ridge”.

Abstract:

Over 70% of the earth is covered by the oceanic crust which is shaped at the Mid-Ocean Ridge (MOR). As the spreading rate drops to less than 12 mm/yr and heat conduction cooling enhanced, the mantle probably directly emplaces on the seafloor. As the end-member of MOR, the slowest-spreading Gakkel Ridge in the Arctic Ocean provide a unique natural laboratory to test the hypothesis. Since the recovery of instruments, like Ocean-bottom Seismometers (OBS) and ocean bottom electro-magnetometer (OBEM), is extremely difficult in the region covered by perennial sea ice, large -scale high-resolution seabed Geophysical detection was considered “impossible”. “Joint Arctic Scientific Middle-ocean ridge Insight Expedition (JASMInE)” project was proposed by Chinese scientists with a broad international participant from 8 countries. The project take advantage of the recently released Icebreaker “Xuelong 2”, which can break 1.5 m ice at a speed of 3 knots. A series of innovative high-tech were used to adapt to concentrated sea ices. I will present observations from the JASMInE project, which includes thickest oceanic crust at mid-ocean ridges and time-dependent crustal thickness. As spreading rate decrease, the active upwelling and associated downwelling due to off-axis Rayleigh-Taylor instabilities play more important roles in the crustal accretion and lead to both spatial and temporal variations in melt supply. The crustal accretion and geodynamic process in ultra-slow spreading ridge then is fundamentally different from elsewhere along mid-ocean ridges.

Main Points:

Deformed “Joint Arctic Scientific Middle-ocean ridge Insight Expedition (JASMInE)” project was conducted with the recently released Icebreaker “Xuelong 2”.
Thickest oceanic crust at mid-ocean ridges and time-dependent crustal thickness are observed in the JASMInE region.
The active upwelling and associated off-axis downwelling due to Rayleigh-Taylor instabilities play more important roles in the crustal accretion of ultra-slow spreading ridges.

Biography: Dr. Jérôme Dyment:

Dr. Tao Zhang is a senior scientist at the Second Institute of Oceanography, Ministry of Natural Resources, China. His research interests are the lithosphere and geodynamics of mid-ocean ridges. He has participated more than 10 scientific expeditions in the Arctic Ocean. He served as the coordinator of the “Joint Arctic Scientific Middle-ocean ridge Insight Expedition (JASMInE)” and the “Arctic Deep Observation for Multi-sphere Cycling (ADOMIC)” project that is part of the United Nations Decade of Ocean Science for Sustainable Development (2021-2030).

More detailed information about the webinar can be found on the InterRidge website (http://interridge.org/webinar/).