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There is public perception that jellyfish populations are increasing on a global scale. While this may be true for some areas, in the eastern Bering Sea, jellyfish populations have fluctuated dramatically during the past three decades.

This project will estimate the age structure and age-specific abundances of the predominant jellyfish in the Bering Sea, Chrysaora melanaster, in order to understand how their population size changes with time. The ultimate goal is to estimate the reproductive capacity and success of this jellyfish in relation to climate variability and to investigate the potential for jellyfish population increases to become a recurring pattern in the Bering Sea under future climate scenarios. In the Bering Sea ecosystem, key questions are whether increases in jellyfish abundance are a recurring phenomenon under climate change and fishing pressure and how these population increases affect ecosystem structure.

Global warming and other climate-related processes are rapidly changing the Arctic Ocean. The carbon cycle is of particular concern in the Arctic because it is unknown how carbon sources and sinks will change and whether these changes will lead to increased greenhouse gas accumulation in the atmosphere. Not much is known about the CO2 cycle in the central Arctic Ocean basins because nearly all measurements have been focused on the Arctic coasts during the low ice summer period. The team's contribution will be to collect shipboard CO2 data during these cruises and deploy CO2, pH and oxygen sensors on existing moorings in collaboration with Woods Hole Oceanographic Institution scientist Rick Krishfield.

The Arctic Ocean is changing rapidly. The changes have important implications for global carbon cycling, global fisheries and ocean acidification. There are many intertwining processes, however, that make future predictions difficult. This project will make important contributions to our understanding of the global carbon cycle and ocean acidification by providing Arctic scientists with high quality carbon cycle data to use in model development and as a baseline for comparison with future carbon parameter measurements.

There is broad interest in understanding firn compaction for a number of reasons, most importantly for better interpretation of paleoclimate from air that becomes trapped within the firn (granular snow, especially on the upper part of a glacier, where it has not yet been compressed into ice). Firn densification involves a number of different mechanisms which leads to vapor movement. We will determine the mechanisms of firn densification and microstructural evolution as a function of depth using dynamic observations of the evolution of the firn using X-ray computed microtomography (µCT).

We will drill an 80-meter firn core at Summit, Greenland and transport it to Dartmouth University. After the field expedition, Steve will work with the team at the university, where we will perform experiments to observe changes based on temperature and stress (due to depth and load). In addition to observing the microstructure as a whole, we can follow the evolution of ice crystals to observe bond formation and bond-breaking under load in detail, as undertaken in some prior studies on snow.

Our project will aid in the understanding of firn and ice microstructure evolution in polar ice sheets. This will aid in understanding ice flow and interpreting paleoclimate reconstruction from ice cores.

This project seeks to better understand the natural variability of hydrology and sediment transport in Arctic glacial lake systems, and to investigate how this variability might be impacted by climate change in the future. Studies such as this one, which captures natural variability across the Arctic at different temporal scales, are necessary to enhance our comprehension of how climate change has impacted and will continue to impact these systems.

In order to improve our paleoclimate reconstructions of these processes, a crucial step is the development of a system model that describes the hydrology, sediment-flux, and sedimentation in glacial lake systems. A main goal of this project is to establish such a model, and to apply it to three glaciated watersheds that span a gradient from the sub-Arctic to high Arctic. The three lakes included in the study are Eklutna Lake (a sub-arctic lake near Anchorage, Alaska), Lake Peters (in the Arctic National Wildlife Refuge, Alaska), and Lake Linné (Svalbard, in the high Arctic). From 2015-2017, field seasons have focused on Lake Peters, where weather stations, sediment traps, ablation stakes, and various other climate monitoring has continued for a total of three years, and sediment cores have been collected to reconstruct paleoenvironmental changes.