Physical forcing of a Western Antarctic Peninsula ecosystem: observations from a coastal ocean observing network at Palmer Station. Travis Miles1, Oscar Schofield1, Douglas G. Martinson2 1Coastal Ocean Observation Laboratory, Rutgers University 2Lamont-Doherty Earth Observatory, Columbia University Introduction High-resolution Seasonal Sampling Local polar marine food webs are undergoing large shifts in composition and structure along the Western Antarctic Peninsula (WAP). Understanding how the regional and local physical ocean and atmosphere affects these food webs is critical to predicting future ecosystem dynamics. The Palmer Station Long-Term Ecosystem Research (PAL-LTER) site is located off Anvers Island, Antarctica at 64o S and 64o W across the narrow Gerlache Strait from the WAP. The Palmer marine ecosystem has seen major shifts in its community structure and ecosystem dynamics for more than twenty years, which has been linked to large scale changes in the WAP climate. The region is characterized by a deep canyon extending to the shelf-break where the Antarctic Circumpolar Current (ACC) follows along the slope, a complex network of islands, the presence of large patches of sea-ice, and frequent synoptic storms with winds regularly in excess of 10 meters per second. In this study we use twenty years of observations of atmospheric and oceanic data to identify mean patterns of variability near Palmer Station, discern the general circulation patterns from three years of Teledyne Webb Slocum glider deployments, and use select glider deployments to describe the impact of storms on hydrography. This study aims to connect large scale global climate change to the local and regional coastal ecosystem. In order to identify the mechanisms that connect the Western Antarctic Peninsula continental shelf and the biologically important Palmer Deep we employed a network of ocean observing tools for the 2011/2012 sampling season. Over 5 Teledyne Webb Slocum gliders were deployed in the Palmer region, sampling the near-shore region from Mid December through late February. All gliders were equipped with Conductivity Temperature and Depth sensors and collect depth-averaged current data using dead reckoning techniques. Select gliders were equipped with optical instrumentation for measuring chlorophyll while others were equipped with Nortek Aquadopp current profilers for measuring currents throughout the water-column. Data and Physical Setting Two locations are continuously sampled each summer as part of the PAL-LTER. Biological and physical measurements are taken here approximately twice a week for the summer season (October through March). Hydrographic data has been collected using a number of different conductivity, temperature and depth (CTD) instruments from a zodiac platform. Salinity and density are derived parameters. Atmospheric data has been collected continuously for over 20 years from a meteorological station located on Gamage Point just in front of Palmer Station. These data include wind speed and direction, barometric pressure, air temperature and relative humidity. Cross-sections and T-S plots show highly variable temperature profiles with consistent warmer water at depth and a highly variable surface layer. There was a general warming trend throughout the season and a shoaling of the warmer deeper waters. In February warm ( > 1oC) temperatures dominated the surface and bottom layers. the system from offshore. Above: Palmer station area and bathymetry in meters. Palmer Deep is to the southwest and offshore is west. Palmer Station is located on Anvers Island, with the Marr Glacier to the north. Salinity was more uniform, though surface waters became more saline in February. The relatively stable salinity profile across all months suggests that despite nearly uniform temperatures in February there are still two independent water masses. Left: Teledyne Webb Slocum glider observations show warm ( > 1 oC ) water extended throughout the water-column over the Palmer Deep. While extensive study has been done on the WAP continental shelf, the mechanism for nutrients and heat to make it into surface waters is unclear. Right: depth of the pycnocline has gradually decreased since the early 1990’s. Periods of locally high wind stress may align with temperature variability in surface waters over short time periods such as in early December and mid-January but the relationship is not clear. Further analysis on local and remote wind forcing is necessary to resolve air-sea interactions. Left: The January glider RU06 was equipped with a Nortek Acoustic Doppler Current Profiler (ADCP), which provided a detailed look at current profiles. Positive values indicate east (top panel) and north (bottom panel). East-West velocity shows banding indicative of tidal motions, with a distinct increase in Eastward velocity during the storm event on the 17th. More mild North-South velocities show an increase in the southward velocity that persists following the storm. Below: Water temperature at Palmer Station has been increasing for the duration of the Palmer LTER with cooler temperatures in the 1990’s and a distinct shift in the 2000’s throughout the upper 100 m. Above: 12-month lowpass winds show a decreasing trend since 1989 with occasional high wind years, particularly 2002 and 2011. Mechanisms for Change Conclusions and Future Work Conditions at Palmer Station are changing, though the connection between the deep continental shelf waters and the upper layers of the coastal ocean are not clear. Individual or a combination of proposed mechanisms that connect deep waters to surface waters may include: Episodic storm driven mixing over the Palmer Deep. Topographic forcing due to the presence of a deep canyon and a complex network of troughs and islands. Remote forcing from periodic eddies and meanders offshore. Temperature cross-sections from glider deployments show a highly complex structure with relatively warm subsurface waters and highly variable warm water in surface layers. Salinity is more uniform and drives light but apparent stable stratification throughout the Summer season. The depth of the pycnocline varies with high-frequency and is likely driven by tidal fluctuations. More analysis is needed to match tidal variability with the depth of the pycnocline. Periodic storms with significant wind-stress impact the region on a regular basis, but the connection to the water-column is not clear. Further analysis, particularly during ADCP glider deployments will be necessary to understand the impact of storms on mixing and heat-flux within the coastal ocean as well as between the air-sea interface. Further Analysis will be performed on glider data to identify spatial variability in hydrographic properties as well as depth-averaged currents due to the complex topography of the Palmer region. Acknowledgments: We would like to thank the LTER science teams. Rich Ianuzzi at LDEO, Sharon Stammerjohn at INSTARR and Hugh Ducklow at MBL. Also we acknowledge the Rutgers Coastal Ocean Observation group and Teledyne Webb for their continued field support. RPSC provided technical support as well as management of the Gamage Point MET station. This work was supported by NSF Grant OPP-02-17282. References: Klink, J.M., and Dinniman, M.S., Exchange across the shelf-break at high southern latitudes, Ocean Sci., 6, 513–524, 2010. 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