Figure 1: The Palmer Long Term Ecological Research program is a multidisciplinary research team with a focus to study the marine ecology of the Southern Ocean along the western Antarctic peninsula, located -64.7° S, -64.05° W
The Antarctic Penninsula is the northern most part of the continent, the only part extending outside the major mark of latitude called the Antarctic Circle. It is approximately 1,200 miles long and is 610 miles south of Cape Horn. Essentially it is a mountain range with peaks rising 9,186 ft. above sea level as you progress farther south. Some consider the mountains to be a geographic continuation of the Andes mountains of South America. Regardless of having almost 95% of its surface and surrounding islands covered by glaciers and ice caps, seasonal melting unveils a rocky soil capable of supporting some plant life. The continent is physically isolated from other surrounding continents like South America, New Zealand, Australia and South Africa.
Figure 2: Illustration of the Antarctic Circumpolar Current (ACC) with the Palmer LTER sampling grid highlighted (blue).
Because of the complexity of ocean dynamics, the ACC serves as a barrier isolating the Antarctic continent from the warm subtropical surface waters residing north of the current. Conversely, the current serves to keep the cold fresh surface polar waters trapped near the continent. That polar surface water is required for sea ice formation so the current serves as the northern limit for sea ice formation. So, the westerlies and the ACC work in tandem to keep the polar oceans cold and allow sea ice to form. And sea ice is critical to the Antarctic ecosystem.
Only along the western margin of Antarctica (including the Antarctic Peninsula) where the ACC skirts directly along the continental margin does the barrier break down. Recent studies along with the long-term time series from the Palmer LTER suggest that this proximity in the western margin along with continental winds and other local processes results in dynamic effects that serve to draw the warm UCDW waters to upwell onto the continental shelf where they are warming the atmosphere, interacting with glaciers causing more rapid glacial melt and are changing the peninsulas ecosystem dynamics. Examples of this impact: The western Antarctic peninsula (WAP) is undergoing the fastest warming on Earth in winter. Eighty seven percent of marine glaciers in the WAP are in retreat (Cook, 2005). The winter seasonal sea ice season is shortened by 3 - 4 months (Stammerjohn et al. (2008) and the Adelie penguins that cannot adapt to the changes in winter sea ice coverage have their local colonies going extinct in the area. These extraordinary changes are affecting trophic interactions throughout the food web and are influencing the way the Antarctic ecosystem functions.
The Research of the Palmer LTER scientists has led to an understanding of the processes and interactions described above and is now focused on monitoring the progression of the changes and additional processes involved in these changes. Interdisciplinary in nature, a host of observational studies, time series data and experimental processes constitute the collection of research methods including nearshore land-based research, and offshore shipboard sampling. There are unattended moorings, autonomous gliders, satellite sensing observations, experiments and modeling all contributing to document and quantify the research. Collectively, these measurements contribute to helping Palmer scientists understand the influence of the physical ocean-atmospheric interactions on the ecosystem and identify the mechanisms influencing the biological productivity within the ecosystem.
Understanding the impact of climate change and how the western Antarctic Peninsula ecosystem responds to that change is the premise to three distinct objectives at the center of Palmer LTER’s research:
- To investigate what mechanisms are impacting changes in species distributions and increased trophic mismatches.
- To understand the physical and ecological mechanisms to climate and ecosystem change.
- To predict/project the future course of ecosystem change in the western Antarctic Peninsula region.
Hypothesis: Key trophic relationships have been altered due to regional warming and increased glacial meltwater inputs and sea ice decline. This has lead to changes in species distributions, increasing trophic mismatches and changes in habitat, food availability, ecosystem dynamics and biogeochemical cycling. Time series measurements, offshore observations, satellite remote sensing, and the use of gliders will aid in better characterizing the climate-trophic interactions.
Hypothesis: Process measurements, manipulative experiments, comparative analysis to other ecosystems, data analysis and modeling will provide comparative data to aid in analyzing ecosystem conditions as the Palmer sampling grid compares the northern and southern transects along the western Antarctic Peninsula. Comparing these two regions will better assess how the climate gradients along the WAP alter the physical-ecological relationships.
Hypothesis: Through intermediate-scaled ship and glider-based surveys and intense process studies the deep cross-shelf troughs along the WAP will be studied to identify the physical and lower trophic level properties supporting the concentration of top predators above the troughs. These troughs serve as focal regions with predictable elevated food resources for top-predators like penguins and influence the foraging ecology and geographic distributions of breeding and wintering populations relative to climate change.