# Surface expression of a wall fountain: application to subglacial discharge plumes

## TL;DR

This study combines laboratory experiments and theoretical modeling to understand the surface expression of subglacial discharge plumes, providing a model that predicts surface features and estimates discharge properties in Greenland fjords.

## Contribution

The paper introduces a novel model that separates the fountain into vertical and horizontal regions, linking surface expression characteristics to flow parameters and applying it to real Greenland data.

## Key findings

- Surface expression dimensions depend on the Froude number.
- The model accurately predicts surface features across various conditions.
- It enables estimation of subglacial discharge properties from surface observations.

## Abstract

We use laboratory experiments and theoretical modeling to investigate the surface expression of a subglacial discharge plume, as occurs at many fjords around Greenland. The experiments consider a fountain that is released vertically into a homogeneous fluid, adjacent either to a vertical or a sloping wall, that then spreads horizontally at the free surface before sinking back to the bottom. We present a model that separates the fountain into two separate regions: a vertical fountain and a horizontal, negatively buoyant jet. The model is compared to laboratory experiments that are conducted over a range of volume fluxes, density differences, and ambient fluid depths. It is shown that the non-dimensionalised length, width, and aspect ratio of the surface expression are dependent on the Froude number, calculated at the start of the negatively buoyant jet. The model is applied to observations of the surface expression from a Greenland subglacial discharge plume. In the case where the discharge plume reaches the surface with negative buoyancy the model can be used to estimate the discharge properties at the base of the glacier.