Thermal Study of Waterfall Ice in Alaska as an Analog for the Formation of the Blood Falls Conduit: A Passage into the Subglacial World

Blood Falls is a release of hypersaline, subglacial brine at the surface of the Taylor Glacier, McMurdo Dry Valleys, Antarctica, providing an accessible portal into an Antarctic subglacial ecosystem. Taylor Glacier is a cold-based glacier that overlies a preglacial marine deposit providing the ultimate source for a basal brine system. Little is known about the origin of this brine, the amount of time it has been sealed below the Taylor Glacier, how the conduit enabling its episodic release exclusively at Blood Falls formed, or what triggers the release. Since its discovery in 1911, the Blood Falls conduit has appeared in the same location each year: a brine outflow at -7C emerging from glacier ice at -17C.

Here we propose to use waterfall ice in Alaska as an analog to study the development and persistence of a conduit of warm fluid through cold ice. In Alaska, 0C water flows through and on the surface of frozen waterfalls despite air temperatures as cold as -30C and ice temperatures as cold as - 15C. This occurs because the freezing process generates heat that warm nearby ice; this process maintains a pathway of warm ice, allowing water to flow despite cold surroundings. Our scientific questions include:

• Over what timescales can the warm pathway shift its position on the waterfall and what conditions drive this movement?
• How sensitive is the warm ice pathway to the flux of water available?
• What conditions allow the restarting of the warm ice path if it stops during the coldest periods of winter?

To answer these, we will observe and measure the changing temperature field at Dragonfly Falls, Alaska, over the winter and use these data to constrain and validate a model of heat flow and the freezing process. We will use a ground-based version of a remote sensing method - thermal infrared imaging - along with direct temperature measurements to monitor the thermal evolution of the waterfall ice. PI Pettit is an early career researcher at UAF. She has studied Taylor Glacier, host to the Blood Falls feature, in the past and a proposal is in review with NSF to continue this work. She recently initiated a study of waterfall ice in Alaska with an emphasis on giving opportunities for undergraduate student researchers. This project will link these two efforts and provide a challenging undergraduate project for a student from Alaska.