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13 results for “PAL LTER”
Thresholds and Regime Shifts at Four LTER Sites (CCE, JRN, PAL, SBC) 1951-2009
The existence and causes of abrupt transitions, thresholds, or regime shifts between ecosystem states is of great concern because the likelihood of such transitions is predicted to increase. The science for measuring and responding to state changes, however, is not well developed. This limitation stems from a lack of data-supported case studies of abrupt transitions in all but a few well-studied ecosystems. We used 30-60 years of data on biological responses and putative drivers from ocean, coastal, polar, and dryland ecosystems to illustrate general approaches to analysis of abrupt transitions. The analyses indicate one case in which the state or response variable (krill abundance) tracked abrupt changes in the driver (Pacific Decadal Oscillation) in a linear fashion. Response variables in other cases (sea cucumber abundance, penguin abundance, and perennial grass production) exhibited hysteretic relationships to drivers (wave intensity, sea ice duration, and monsoonal rainfall amounts, respectively) through a variety of response mechanisms. The analyses illustrate that 1) a suite of common concepts and approaches can be used across disparate systems, 2) there are generally insufficient data for the use of leading indicators, particularly considering the abruptness of transition relative to the lifespan of long-lived organisms, 3) information on spatiotemporal context is useful for comparing transitions in similar systems, and 4) ancillary information from associated experiments and observations is critical for interpreting response-driver relationships.
Merged discrete water-column data from PAL LTER research cruises along the Western Antarctic Peninsula, from 1991 to 2024.
Water samples are collected throughout the water column along the Western Antarctic Peninsula at regular LTER grid stations where CTD casts are preformed and in surface waters at underway stations, where CTD casts are not done, using the ship's flow-through seawater system. This dataset is the compilation of water samples collected at these stations, merged from other PAL-LTER datasets. Data includes water column Chlorophyll and Phaeopigment concentrations; phytoplankton accessory pigments -including other chlorophyll's (e.g. chlorophyll b), xanthophylls, and carotenes; primary production rates; bacterial production; dissolved organic carbon; particulate organic carbon and nitrogen; dissolved inorganic nutrients; dissolved oxygen, and dissolved inorganic carbon and alkalinity. Measurements of phytoplankton Fv/Fm measured using a FIRe (Fluorescence Induction and Relaxation) fluorometer are also included, though caution is urged as FIRe data has not been corrected nor QCed. Conductivity, temperature, depth, and associated data from instruments on the sampling rosette (e.g. PAR, beam transmission) for each sampling depth are also included. Phytoplankton accessory pigment data is unavailable for the LMG10-01 cruise due to instrumentation problems and for the LMG12-01 cruise due to a freezer failure which resulted in the loss of samples. Dissolved oxygen measurements were discontinues after 2012, and thus no data is available from 2013 onwards. Dissolved Organic Carbon data is unavailable after 2012 due to instrumentation problems. There is no Particulate Organic Carbon data for cruise PD94-01.
Merged discrete water-column data from annual PAL LTER field seasons at Palmer Station, Antarctica, from 1991 to 2025.
Water samples are collected throughout the water column at regular stations within the Palmer LTER region at Palmer Station, on Anvers Island, Antarctica. CTD casts are preformed and water collected using go-flo bottles or a rosette. Near-surface waters are also sampled occassionally at the Palmer Station seawater intake (pumphouse). This dataset is the compilation of water samples collected at these stations, merged from other PAL-LTER datasets. Data includes water column Chlorophyll and Phaeopigment concentrations; phytoplankton accessory pigments -including other chlorophyll's (e.g. chlorophyll b), xanthophylls, and carotenes; primary production rates; bacterial production; dissolved organic carbon; particulate organic carbon and nitrogen; dissolved inorganic nutrients; dissolved oxygen, and dissolved inorganic carbon and alkalinity. Measurements of phytoplankton Fv/Fm measured using a FIRe (Fluorescence Induction and Relaxation) fluorometer are also included, though caution is urged as FIRe data has not been corrected nor QCed. Conductivity, temperature, depth, and associated data from instruments on the CTD/sampling rosette (e.g. PAR, beam transmission) for each sampling depth are also included. Phytoplankton accessory pigment data is unavailable for the Palmer 2009-2010 season due to instrumentation problems and for the Palmer 2011-2012 season due to a freezer failure which resulted in the loss of samples. There is a temporary data gap for the Palmer 2015-2016, 2016-2017, 2019-2020, 2020-2021, 2023-2024, and 2024-2025 seasons because those samples have not been analyzed yet. Dissolved oxygen measurements and dissolved inorganic carbon/alkalinity measurements are not available for any season. Dissolved Organic Carbon data is unavailable after 2012 due to instrumentation problems. There is no Particulate Organic Carbon after the 2012 season.
Seasonal sea ice indices including the timing of ice-edge advance and ice-edge retreat (in year day), the ice season duration (in days) and number of actual ice days (versus open water days) within the ice season, extracted for various PAL LTER sub-regions West of the Antarctic Peninsula and derived from passive microwave satellite data for 1979/80 to 2023/24 ice seasons.
Seasonal sea ice indices including the timing of ice-edge advance and ice-edge retreat (in year day), the ice season duration (in days) and number of actual ice days (versus open water days) within the ice season, extracted for various PAL LTER sub-regions West of the Antarctic Peninsula and derived from passive microwave satellite data for 1979/80 to 2023/24 ice seasons. The ice season duration is defined as the time elapsed between day of ice-edge advance and day of ice-edge retreat within a given sea ice year, which begins mid-February (mean minimum of summer sea ice extent for the Southern Ocean) and ends the following mid-February. See Stammerjohn et al (2008, JGR) for further details.
Average monthly sea ice coverage for various PAL LTER sub-regions West of the Antarctic Peninsula derived from passive microwave satellite data, 1978 - June 2024.
Monthly sea ice coverage derived from passive microwave satellite measurements and extracted for various PAL LTER subregions. Several different sea-ice metrics are provided including (1) monthly sea-ice extent, sea-ice area, and open-water area (km^2) extracted for the greater WAP region (from the AP to 80W) and for 3 PAL LTER grid regions: the original PAL grid (000-900 lines), the PAL 'DSR' grid (200-600 lines), and the PAL 'new' grid (-200 to 600 lines); and (2) monthly sea-ice concentration (%) extracted for small PAL subregions, including the nominal penguin foraging areas (~200km by ~200km) southwest of King George Island (KGI), Anvers, Avian and Charcot islands, as well as for Marguerite Bay (~140km by ~140km) (inland of the area defined for Avian).
Average yearly sea ice coverage for various PAL LTER sub-regions West of the Antarctic Peninsula derived from passive microwave satellite data, 1979 - 2023.
Annual sea ice coverage derived from passive microwave satellite measurements and extracted for various PAL LTER subregions. Several different sea-ice metrics are provided including: monthly sea-ice extent, sea-ice area, and open-water area (km^2) extracted for the greater WAP region (from the AP to 80W) and for 3 PAL LTER grid regions: the original PAL grid (000-900 lines), the PAL 'DSR' grid (200-600 lines), and the PAL 'new' grid (-200 to 600 lines).
Elemental composition, respiration, and excretion measurements of pteropods collected from the PAL LTER research cruises along the Western Antarctic Peninsula 2017-2019.
Pteropods (pelagic snails) are abundant zooplankton in the Southern Ocean where they are important grazers of phytoplankton, prey for higher trophic levels, and sensitive to environmental change. In this study, the effects of warming seawater temperatures and shifting food availability on Limacina helicina antarctica metabolism (respiration and excretion) were determined by conducting shipboard experiments that exposed pteropods to a range of temperatures and phytoplankton (food) concentrations. Pteropods and all other macrozooplankton were collected with a 2 m square frame Metro net (700 µm mesh), towed obliquely to depths up to 120 m (Ross et al., 2008; Steinberg et al., 2015), or with shallower (0-50 m), vertical tows if pteropods were very abundant. Pteropods were exposed to varying temperature and food conditions for 12 hours and respiration and excretion were measured. Incubations were also conducted with non-shelled pteropod species and shelled pteropod, Clio pyramidata, measuring pteropod respiration under in situ conditions. Finally, a CO2 perturbation experiment measuring L. h. antarctica metabolism (respiration and excretion) under pre-industrial and elevated dissolved CO2 conditions at ambient temperature in filtered seawater (no food), during the 2018 PAL LTER research cruise. Results reveal the metabolic response of pteropods to ocean variability, increase our understanding of the role of zooplankton in biogeochemical cycles, and help predict future responses to climate change.
Shell lengths of pteropod, Limacina helicina antarctica, collected from the PAL LTER sediment trap along the Western Antarctic Peninsula, 2004 - 2018, and from net tows 2017-2018.
Pteropod, Limacina helicina antarctica, is an abundant zooplankton along the Western Antarctic Peninsula (WAP) and prey for higher trophic organisms. Changes in the pteropod (pelagic snail) phenology (life history) have important implications for regional food web dynamics. Pteropod shell lengths were collected from the PAL LTER sediment trap located along the northern continental shelf of the PAL LTER sampling grid, 2004-2018. PAL LTER has deployed a time-series trap near 64.5° S, 66.0° W since late 1992. The trap is moored in 300 m depth and collects sinking particles at 170 m. Pteropod samples are stored in 21 sample collection bottles on the sediment trap that were prepared with a Milli-Q deionized water rinse and filled with 7.5 g NaCl l-1 solution and 2% borate-buffered formalin in filtered seawater (34 ppt), with a final salinity concentration of 41 ppt. L. h. antarctica shell lengths also collected during the PAL LTER 2018 January offshore cruise and for four months at Palmer Station, Anvers Island (November 2017 to February 2018). L. h. antarctica and all other macrozooplankton collection on the PAL LTER cruise are performed with a 2 m square frame Metro net (700 µm mesh), towed obliquely to a depth of 120 m. At Palmer Station, pteropods are collected with a 1 m x 1 m square frame Metro net (700 µm mesh) and a 1 m diameter ring net (200 or 500 µm mesh), towed obliquely to a depth of ~50 m. Shell lengths are determined by measuring from the opening of the shell aperture directly across the diameter of the shell. The shell lengths analyzed within the WAP region are used to determine phenology patterns in pteropod population dynamics and changes thereof over time.
Conductivity Temperature Depth (CTD) sensor profile data binned by depth from PAL LTER annual cruises, 1991 - 2017 (ongoing).
Since 1991 (and ongoing), the PAL LTER program has deployed a SeaBird 911+ CTD mounted on a 24-bottle rosette during annual (Austral Summer) cruises plus a few supplemental cruises at other times of the year. An equal area grid oriented parallel to the average coast provides the basis for sampling, as well as specific process studies and on-the-fly scientific needs. The CTD-rosette is lowered into the ocean (usually to just above the sea-floor) using the ship's conductive-wire winch. Data is collected and displayed real-time to ensure quality and make decisions about where to collect seawater with the bottles. Bottle data is typically collected extensively in the seasaonal mixed layer and pycnocline, plus at Tmin, in the permament pycnolcine and at Tmax and Smax, as well as near the bottom. Bottle data allows measurement adn calculation of additional variables and helps ensure quality data collected via sensors. Sensors include: Pressure, Conductivity (for Salinity), Temperature, Oxygen, Transmissometer, Flourometer, Photosynthetically Available Radiation (PAR/Irrandiance). Additional Bottle Data Variables include: Phosphate, Silicate, Nitrite, Nitrate, Ammonium. After each cruise, Temperature, Conductivity and Oxygen sensors are calbrated and post-crusie processing is applied, making use of pre- and post- cruise calibrations as well as SeaBird software and algorithms for getting the best quality data. Each profile is then inspected for any issues and if needed, suitable corrections are made such as using secondary sensors (temperature, conductivity and oxygen all currently measured in duplicate), using the upcast, or flagging the data as bad.
Sources of oceanic freshwater content along the western Antarctic Peninsula (PAL-LTER Study Region) determined by the stable isotope composition (d18O) of seawater.
The oceanic distribution of d18O is determined largely by the same processes that control salinity. Surface d18O reflects the magnitude and spatial distribution of freshwater inputs, and it is a conservative tracer in the ocean interior. The great benefit of d18O is obtained from the circumstances under which it exhibits behavior different to that of salinity. One such circumstance derives from the salinity and d18O values in precipitation, with salinity being constant with latitude (typically zero), while in general d18O in precipitation becomes progressively isotopically lighter toward the poles. This results in glacial ice (which derives from high-latitude precipitation) being very isotopically light, enabling d18O to be a useful tracer of glacial discharge to the ocean (e.g., Schlosser et al. 1990; Weiss et al. 1979). Another difference occurs in regions influenced by sea ice, which greatly affects salinity during its formation/melt cycle but has only minimal impact on d18O. This decoupling of the two tracers allows them to be used in tandem to quantitatively separate freshwater inputs from sea ice melt and those from meteoric sources (precipitation plus glacial discharge). For this, a simple three-endmember mass balance can be used. For details please see Meredith, M. P., H. J. Venables, A. Clarke, H. W. Ducklow, M. Erickson, M. J. Leng, J. T. M. Lenaerts, and M. R. van den Broeke. 2013. The freshwater system west of the Antarctic Peninsula: Spatial and temporal changes. Journal of Climate 26:1669-1684.
Data from oceanographic moorings deployed on the Antarctic Continental Shelf (and inshore) west of the Antarctic Peninsula as part of the Palmer Long Term Ecological Research Project (PAL LTER), 2007 - 2017.
Oceanographic moorings have been deployed beginning in January 2007 on the Antarctic Continental Shelf (and inshore) west of the Antarctic Peninsula as part of the Palmer Long Term Ecological Research Project (PAL LTER). The moorings have been located at several sites, each deployment lasting typically just under one year, as moorings are recovered at the beginning of the PAL LTER annual January cruise and deployed at the end of the cruise. Some sites have had mutliple deployments (ie, multiple years) while others have a mooring for only one year. Any given year had between 1 and 5 deployments. The moorings were subsurface typically with tops about 50 meters below the surface attempting to always sample the winter mixed layer and below. Each mooring consisted of a thermister string designed to well-capture the vertical temperature structure and betwee 1 and 7 current meters designed to capture the main features of the current structure. A conductivity cell was deployed infrequently to obtain salinity at a single depth.
Palmer (PAL) log of events aboard Palmer LTER cruises off the coast of the Western Antarctic Peninsula (cruise happenings ordered by time) is a meta dataset, including lat-lon, datetime, activity, events, etc, 1991 - 2019.
The event log for the Palmer LTER research cruises provides a mapping of sampling and other research activities to spatial, temporal and other variables. Event numbers are used to coordinate relational indexes and provide users of the data with a high-level index for relating measurements across research components.
Palmer Station Antarctica (PAL) Long Term Ecological Research Network (LTER)
Measurements made under the Long Term Ecological Research Network (LTER) Palmer Station Antarctica (PAL) program.
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