The vertical structure and entrainment of subglacial melt water plumes

Abstract

The accelerated melting of Greenland's glaciers contributed to a net global mean sea level rise of 7.5 mm during the years 1992-2011(Church et al., 2011. Around Greenland, the basal and surface melt water enters the ocean largely through glacial fjords, mainly as subglacial discharge at the grounding lines of marine-terminating glaciers or as subglacial melt fluxes at the ice-ocean interface (Straneo & Cenedese, 2015). Increased melting at the ice-ocean interface it thought to be responsible for the acceleration of many of Greenland's marine terminating glaciers and thus to have contributed to the sea level rise. Some large Greenland fjords are covered with ice tongues of marine-terminating glaciers such as the Nioghalvfjerdsfjorden, also called 79°N glacier fjord (Mayer et al., 2018), and the Petermann Gletscher (Münchow et al., 2014). For these glaciers the link between submarine

High-resolution simulations of the plume dynamics in an idealized 79°N Glacier cavity using adaptive vertical coordinates

“…Where the ocean is covered by glacier ice, there is a no-slip boundary condition at the sea surface (Burchard et al, 2022). This friction at the ice-ocean interface is implemented in GETM according to the law-of-the-wall with a roughness length z 0,ice , similar to bottom friction.…”

“…We implemented the subglacial melt formulation by Burchard et al (2022). This parametrization, based on the three-equation model (D. M. Holland & Jenkins, 1999), is suitable for high vertical resolutions under the ice.…”

“…The melt layer is a thin layer at the ice-ocean interface, that is not resolved but parametrized in our model. For a detailed discussion, see Burchard et al (2022).…”

“…A challenge for ocean models is to provide sufficiently high resolution in a glacier fjord to accurately simulate the two plumes. It has been shown that the subglacial plume and particularly its entrainment layer require a vertical resolution of about 1 m or better to correctly model the plume development and the associated melting (Burchard et al, 2022). This is hard to achieve in most ocean models, because of the stark contrast in vertical scales between the fjord depth of several hundred meters and the plume thickness on the order of one to ten meters.…”

“…We created an idealized 2D-vertical simulation of the 79NG fjord using AVC together with a melt parametrization (Burchard et al, 2022) that is suitable for high vertical resolution at the ice-ocean interface. To our knowledge, this is the first model to use stratification-zooming coordinates like AVC in a glacier cavity.…”