Variability Of Ice Cover Research Articles

ANALYSIS OF INTERANNUAL AND SEASONAL VARIABILITY OF ICE COVER IN ANIVA BAY AND LA PEROUSE STRAIT ACCORDING TO EARTH REMOTE SENSING DATA

Based on the data of satellite observations of the ice cover with the use of geoinformation technologies, an analysis of the interannual and seasonal variability of ice cover in Aniva Bay and La Perouse Strait has been made. It is established that there is a tendency for a decrease in ice cover by 2.5% in Aniva Bay, and in La Perouse Strait – by 11% for the period from 1979 to 2016. It is revealed that Aniva Bay is the only water area with a tendency of increasing ice cover. Based on the analysis of the dynamics of ice cover anomalies relative to the climatic standard norm of 1981- 2010, periods with the predominance of its positive and negative values and years with the highest and lowest values have been marked. It is shown that the ice cover of La Perouse Strait and Aniva Bay has the greatest interrelation with the ice cover in the extreme southern part of the Sea of Okhotsk with a correlation coefficient of 0.76 and 0.66, respectively. The typing of winters according to the severity of ice conditions has been performed according to which it is determined that the sum of severe and extremely severe types of winters in Aniva Bay is higher than that in La Perouse Strait. Analysis of the intra-seasonal course of ice cover made it possible to determine the mean dates for the appearance and disappearance of the ice in Aniva Bay and La Perouse Strait, as well as the duration of the ice period. Aniva Bay is characterized by almost complete filling with ice, which occurs here in severe winters from February 10 to March 10. La Perouse Strait is filled with ice in the severe winters only by 70% - from 15 to 25 of February.

Fine-scale spatial variation in ice cover and surface temperature trends across the surface of the Laurentian Great Lakes

The effects of climate change on north temperate freshwater ecosystems include increasing water temperatures and decreasing ice cover. Here we compare those trends in the Laurentian Great Lakes at three spatial scales to evaluate how warming varies across the surface of these massive inland water bodies. We compiled seasonal ice cover duration (1973–2013) and lake summer surface water temperatures (LSSWT; 1994–2013), and analyzed spatial patterns and trends at lake-wide, lake sub-basin, and fine spatial scales and compared those to reported lake- and basin-wide trends. At the lake-wide scale we found declining ice duration and warming LSSWT patterns consistent with previous studies. At the lake sub-basin scale, our statistical models identified distinct warming trends within each lake that included significant breakpoints in ice duration for 13 sub-basins, consistent linear declines in 11 sub-basins, and no trends in 4 sub-basins. At the finest scale, we found that the northern- and eastern-most portions of each Great Lake, especially in nearshore areas, have experienced faster rates of LSSWT warming and shortening ice duration than those previously reported from trends at the lake scale. We conclude that lake-level analyses mask significant spatial and temporal variation in warming patterns within the Laurentian Great Lakes. Recognizing spatial variability in rates of change can inform both mechanistic modeling of ecosystem responses and planning for long-term management of these large freshwater ecosystems.

Features of the sea ice cover variability in the Tatar Strait (Japan Sea) in connection with the regional atmosphere circulation

Features of the sea ice cover variability in the Tatar Strait (Japan Sea) in connection with the regional atmosphere circulation

Seasonal and interannual variability of pan-Arctic surface mixed layer properties from 1979 to 2012 from hydrographic data, and the dominance of stratification for multiyear mixed layer depth shoaling

Using 21,406 hydrographic profiles from 1979 to 2012, we present the first observational, pan-Arctic assessment of Mixed Layer (ML) properties, including quantification of seasonal and interannual variability, and identification of multiyear ML depth shoaling.Arctic Mixed Layer Depths (MLDs) vary strongly seasonally, being deeper (∼25 to >50m) in winter than summer (∼5–30m). Eastern Arctic MLDs (regional mean ∼20m in summer, ∼70 to 100+m in winter) are deeper than western Arctic MLDs (∼8m in summer, 30m in winter). Patchiness, likely related to small-scale sea ice cover variability, is large – standard deviations ∼40% of the regional mean.By binning data into 6 regions (i.e., Chukchi Sea, Southern Beaufort Sea, Canada Basin, Makarov Basin, Eurasian Basin and Barents Sea), we quantify regional seasonal climatologies and interannual variability of ML depth, temperature and salinity. In most regions, ML changes are consistent with seasonal ice melt (∼1–3m) with a ∼1.5 times greater sea ice change required in the western Arctic than in the eastern Arctic. In the Southern Beaufort Sea and the Canada Basin, however, other freshwater sources contribute to observed seasonality.MLDs are significantly correlated with wind only during ice-free times, and even then the relationship only explains 1–20% of the MLD variance. The same wind is 2–3 times more effective at deepening the ML in the eastern Arctic than in the (more stratified) western Arctic. Changes in underlying stratification (Δρ) explain ∼60% of the MLD variance, with MLDs proportional to Δρ−0.45. Weak eastern Arctic stratification permits a wind–MLD coupling comparable to an Ekman model, while the stronger western Arctic stratifications reduce the wind’s effectiveness by a factor of 6.Remarkably, record-length (up to 30-year) trends indicate almost ubiquitous ML shoaling, order 0.5–1m/yr, both in winter and summer over all the high Arctic (Canada, Makarov and Eurasian basins) and in winter in the peripheral seas (Chukchi, Southern Beaufort and Barents seas), coincident with ML freshening and increased stratification, while wind speed trends are either not significant or decreasing. The freshwater change related to this shoaling is small – order 100km3/yr. In contrast, the Southern Beaufort Sea shows ML deepening, coincident with decreasing stratification, possibly related to river water being driven away from the coast. Changes in T–S space suggest decreased convection in the Eurasian Basin in the 2000s.Although in these results it is the absence of sea ice that allows wind-driven ML deepening, the dominance of stratification over wind in determining MLD suggests that even small changes in the Arctic freshwater budget may control MLD variability, with implications for mixing nutrients and heat up into the surface layer and photic zone.

Winter thermal structure of Lake Superior

Moorings equipped with thermistors that span the water column were deployed at up to seven locations throughout Lake Superior from October 2005 through May 2013. This year‐round, multi‐year, multi‐location, full water‐column record of the thermal structure reveals significant inter‐annual and spatial variability in Lake Superior's winter heat content, thermocline depth, and phenology. There is a stark contrast in thermal structure between the cold, icy winter of 2009, during which strong negative stratification formed, and the much warmer winter of 2012, during which the stratification was much weaker. Significant inter‐annual and spatial variability was also observed in ice cover, which influenced heat content. Ice cover significantly inhibits heat flux between the lake and the atmosphere, and spatial variability in ice cover translates into spatial variability in end‐of‐winter heat content. This is found to be preserved through the spring warming season, and is strongly correlated with variability in the timing of the onset of summer stratification, with regions that have warmer end‐of‐winter water columns stratifying earlier than regions with colder end‐of‐winter water‐columns. Observed spring warming rates appear to depend not on mooring depth, but on regionally averaged depth; this suggests the existence of a lateral mixing mechanism.

Model‐simulated interannual variability of Lake Erie ice cover, circulation, and thermal structure in response to atmospheric forcing, 2003–2012

Interannual variability of ice cover, circulation, and thermal structure in Lake Erie for 2003–2012 was investigated using a three‐dimensional hydrodynamic model coupled with ice processes. The model reproduced minima of ice extent in the winters of 2006 and 2012 (mild winters), as well as maxima in 2009 and 2011 (severe winters) in agreement with the observational analysis. The model reasonably captured ice thicknesses, seasonal variation of the mean surface temperature, and lake circulation. The model results showed early onset of stratification in March after the almost ice‐free winter of 2012. In the mild winters, the coastal current speed was significantly higher than the 9 year mean, since the larger open water region due to less ice cover allowed the more effective wind driven circulation. In the severe winters, the lake circulation was slowed because the packed ice reduced wind stress on the water surface. Seasonal means of coastal current speed ranged from 3.9 cm/s in the severe winter (January to March mean) of 2009 to 7.2 cm/s in the mild winter of 2012. The variation was much larger than in the other seasons (±0.6 cm/s). The results imply that decreasing ice cover could lead to a more energetic coastal circulation in winter, which could influence lake turbidity, material transport, and nearshore waves. Finally, the interannual variation of ice cover is discussed in relation to teleconnection patterns. The ice minimum (maximum) in the winter of 2006 (2009) can be explained by the intermittent positive (negative) North Atlantic Oscillation that occurred in January (December to January).

Dinocyst-based reconstructions of sea ice cover concentration during the Holocene in the Arctic Ocean, the northern North Atlantic Ocean and its adjacent seas

Sea ice cover extent expressed in terms of mean annual concentration was reconstructed from the application of the modern analogue technique to dinocyst assemblages. The use of an updated database, which includes 1492 sites and 66 taxa, yields sea ice concentration estimates with an accuracy of ±1.1/10. Holocene reconstructions of sea ice cover were made from dinocyst counts in 35 cores of the northern North Atlantic and Arctic seas. In the Canadian Arctic, the results show high sea ice concentration (>7/10) with little variations throughout the interval. In contrast, in Arctic areas such as the Chukchi Sea and the Barents Sea, the reconstructions show large amplitude variations of sea ice cover suggesting millennial type oscillations with a pacing almost opposite in western vs. eastern Arctic. Other records show tenuous changes with some regionalism either in trends or sea ice cover variability. During the mid-Holocene, and notably at 6 ± 0.5 ka, minimum sea ice concentration is recorded in the eastern Fram Strait, northern Baffin Bay and Labrador Sea. However, this minimum cannot be extrapolated at the scale of the Arctic and circum-Arctic. The comparison of recent observations and reconstructions suggests larger variations in the Arctic sea ice cover during the last decades than throughout the Holocene.

Temporal and Spatial Variability of Great Lakes Ice Cover, 1973–2010*

Abstract In this study, temporal and spatial variability of ice cover in the Great Lakes are investigated using historical satellite measurements from 1973 to 2010. The seasonal cycle of ice cover was constructed for all the lakes, including Lake St. Clair. A unique feature found in the seasonal cycle is that the standard deviations (i.e., variability) of ice cover are larger than the climatological means for each lake. This indicates that Great Lakes ice cover experiences large variability in response to predominant natural climate forcing and has poor predictability. Spectral analysis shows that lake ice has both quasi-decadal and interannual periodicities of ~8 and ~4 yr. There was a significant downward trend in ice coverage from 1973 to the present for all of the lakes, with Lake Ontario having the largest, and Lakes Erie and St. Clair having the smallest. The translated total loss in lake ice over the entire 38-yr record varies from 37% in Lake St. Clair (least) to 88% in Lake Ontario (most). The total loss for overall Great Lakes ice coverage is 71%, while Lake Superior places second with a 79% loss. An empirical orthogonal function analysis indicates that a major response of ice cover to atmospheric forcing is in phase in all six lakes, accounting for 80.8% of the total variance. The second mode shows an out-of-phase spatial variability between the upper and lower lakes, accounting for 10.7% of the total variance. The regression of the first EOF-mode time series to sea level pressure, surface air temperature, and surface wind shows that lake ice mainly responds to the combined Arctic Oscillation and El Niño–Southern Oscillation patterns.

Lake Ladoga ice phenology: Mean condition and extremes during the last 65 years

AbstractWinter conditions play an important role for the largest lake in Europe—Lake Ladoga. The ice cover lasts for 171 ± 3 days on average from the early November until the mid‐May. We investigated the ice regime of Lake Ladoga using a constructed ice database of aircraft surveys and satellite images. More than 1250 surveys of the lake's ice cover from 1943 to 2010 were collected and analysed to determine mean and extreme ice conditions for winters of different types of severity. The time series of ice cover percentage over the lake was plotted. On average, 18 observational ice charts were made every winter. Individual ice phenology records show considerable year‐to‐year variation. For this reason, records typically have been combined and analysed as groups (categories). Extremely cold winters were determined as winters with complete ice cover that lasts more than three months which is approximately 90% quartiles from all winters with complete ice cover. The lake surface was completely covered with ice for more than three months during 5 seasons. Extremely warm winters when the maximum ice cover was less than 70% of the lake area occurred during 5 seasons as well. A basic relationship between the winter severity as winter maximum of accumulated freezing degree‐days (AFDD) and the earlier derived Relative Ice Cover Index (RICI) was established. We have used teleconnection indices such as North Atlantic Oscillations (NAO) and Arctic Oscillation (AO) for the period from October to May for estimation of different types of Lake Ladoga's ice conditions. The AO index in winter months and local winter maximum of AFDD explained much of the interannual variation in ice cover. Copyright © 2011 John Wiley & Sons, Ltd.

Regional climatic drivers of synchronous zooplankton dynamics in north-temperate lakes

The role that climate plays in determining the temporal dynamics of freshwater zooplankton is poorly understood, despite its potential to synchronize population dynamics on a regional basis. We quantify the spatial synchrony of common zooplankton taxa among lakes in the Dorset, Ontario, area and investigate the climatic mechanisms responsible for these patterns at both annual and seasonal scales. We show that the dynamics of several taxa are characterized by similar patterns of abundance among lakes across the region, suggesting a synchronising effect of climate on zooplankton population abundances. Using multiple regression analyses to compare zooplankton dynamics with climatic and in-lake variables, we find that El Niño – Southern Oscillation (ENSO) events and ice cover variability are among the most important predictors of synchrony at annual and seasonal scales, particularly for Leptodiaptomus and Bosmina. Leptodiaptomus, a dominant herbivore in these lakes, had decreased abundances in years with earlier ice-off dates and shorter periods of ice cover. Secchi depth was also synchronous and appeared to respond to regional meteorological factors (spring temperature and precipitation, ice duration). A warming climate with the ability to modify ice and ENSO dynamics, as well as temperature and precipitation patterns, may also alter the structure and dynamics of zooplankton communities in north-temperate lakes.

Calibration of an ice-core glaciochemical (sea-salt) record with Sea-ice variability in the Canadian Arctic

AbstractCorrelation between glaciochemical time Series from an ice core collected on Devon Ice Cap, Nunavut, Canada, and gridded time Series of Sea-ice concentrations reveals Statistically Significant inverse relationships between Sea-salt concentrations (mainly Na+, Mg2+and Cl–) in the ice core and Sea-ice cover in Baffin Bay over the period 1980–97. An empirical orthogonal function (Eof) analysis performed on all major ions Shows that the dominant mode of glaciochemical variability (Eof1) represents a Sea-salt Signal, which correlates best with Sea-ice concentration in Baffin Bay. On a Seasonal basis, the Strongest and most Spatially extensive anticorrelations are found in Baffin Bay during the fall, followed by Spring, Summer and winter. These results Support the notion that increased open-water conditions in Baffin Bay during the Stormy Seasons (fall and Spring) promote increased production, transport and deposition of Sea-salt aerosols on Devon Ice Cap. Comparison of ice-core time Series of Eof1, δ18O and melt percentage, with air temperatures recorded in Upernavik, Greenland, Suggests that ice-cover variations in Baffin Bay over the past ∽145 years were dynamically rather than thermodynamically controlled, with periods of Strengthened cyclonic circulation leading to increased open-water conditions, and a greater Sea-salt flux on Devon Ice Cap.

Phytoplankton in the Beaufort and Chukchi Seas: Distribution, dynamics, and environmental forcing

Time-series of remotely sensed distributions of phytoplankton, sea ice, surface temperature, albedo, and clouds were examined to evaluate the impact of the variability of environmental conditions and physical forcing on the phytoplankton distribution in the Beaufort and Chukchi Seas. Large-scale distributions of these parameters were studied for the first time using weekly and monthly composites from April 1998 through September 2002. The basic data set used in this study are phytoplankton pigment concentration derived from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), ice concentration obtained from the Special Sensor Microwave Imager (SSM/I) and surface temperature, cloud cover, and albedo derived from the Advanced Very High Resolution Radiometer (AVHRR). Seasonal variations of the sea ice cover was observed to be the dominant environmental factor as the ice edge blooms followed the retreating marginal ice zones northward. Blooms were most prominent in the southwestern Chukchi Sea, and were especially persistent immediately north of the Bering Strait in nutrient- rich Anadyr water and in some fronts. Chlorophyll concentrations are shown to increase from a nominal value during onset of melt in April to a maximum value in mid-spring or summer depending on location. Large interannual variability of ice cover and phytoplankton distributions was observed with the year 1998 being uniquely associated with an early season occurrence of a massive bloom. This is postulated to be caused in part by a rapid response of phytoplankton to an early retreat of the sea ice cover in the Beaufort Sea region. Correlation analyses showed relatively high negative correlation between chlorophyll and ice concentration with the correlation being highest in May, the correlation coefficient being -0.45. 1998 was also the warmest among the five years globally and the sea ice cover was least extensive in the Beaufort-Khukchi Sea region, partly because of the 1997-98 El Nino. Strong correlations were noted between ice extent and surface temperature, the correlation coefficient being highest at - 0.79 in April, during the onset of the bloom period

Variation in sea ice cover on the east coast of Canada from 1969 to 2002: climate variability and implications for harp and hooded seals

There is growing evidence that global change and climate variability are affecting sea ice dynamics in northern and eastern Canada. Such variability could have serious consequences for harp seals Pagophilus groenlandicus and hooded seals Cystophora cristata, which congregate to whelp on ice every February and March in the Gulf of St. Lawrence and off Newfoundland. We com- bined a numerical and spatial analysis of weekly averages of ice data to examine the variability of ice cover in eastern Canada during February and March, 1969 to 2002. Sea ice cover varied cyclically in eastern Canada during that time and exhibited a period of light ice years between 1996 and 2002. Spring thaw generally results in a significant reduction of sea ice cover throughout much of the study area, although some regions exhibit increases associated with oceanographic phenomena. Heavy ice years correlate with positive spring North Atlantic Oscillation (NAO) conditions and an in-depth analysis of highly anomalous (+/-) years (1970, 1972, 1981, 1993 and 2001) revealed consistent spa- tial and numerical patterns in ice dynamics. During light ice years, a synchronous and dramatic reduction in sea ice cover occurred in the Gulf and off eastern Newfoundland in the first and second week of March, coinciding with peak pupping periods for harp seals. Light ice years and rapid reduc- tions in sea ice represent unquantified risks for pagophilic seals. These include increases in neonatal mortality, changes in food availability for pups and, possibly, increased risk of epizootics due to crowding on whelping patches. The magnitude of these risks may increase if observed changes in cli- mate reduce sea ice cover in eastern Canada as they have in the Arctic. Patterns in sea ice cover and NAO conditions can be incorporated into short- and long-term management schemes aimed at ensur- ing the sustainability of commercially exploited pagophilic seal populations.

The influence of Asian summer monsoon variability on the water balance of a Tibetan lake

Past water-balance changes in Tibetan lakes are generally attributed to changes in the strength of the summer monsoon. However, the water balance of a lake reflects many different water fluxes, which are controlled by many climatic and hydrologic processes. In this research, weather data and evaporation models are used to determine the climatic cause of a recent water-balance change in Ahung Co, a lake in central Tibet. Between 1995 and 2001, lake level rose at least 20 cm and the lake began to overflow. Results indicate that an increase in summer monsoon precipitation over the lake and drainage basin is responsible for the rise in lake level. Stronger monsoon conditions between 1995 and 2001 also led to decreased lake evaporation and basin evapotranspiration due to increased clouds and humidity. This contributed to the rise in lake level, but to a much smaller extent than the increase in monsoon precipitation. Lake evaporation during the spring and fall was also reduced between 1995 and 2001 due to longer lasting ice cover. Variations in ice cover play a small role in the overall water balance of Ahung Co, however, because the lake area is small compared to the drainage basin area. If these results hold true for the past, water-balance fluctuations inferred from the geochemistry of sediments from Ahung Co provide a record of variations in monsoon precipitation during the Holocene.

Large-Scale Climatic Controls on Lake Baikal Ice Cover

Abstract Long-term records of winter ice duration, formation, and breakup dates (1869–1996) and maximum thickness (1950–95) on Lake Baikal are analyzed to determine the nature of temporal trends and the relationship with the large-scale atmospheric circulation. There are highly significant trends of decreasing ice duration (and thickness) over the period, associated with later ice formation and earlier breakup dates. These trends are broadly in line with those of winter air temperatures in the region. Variability in Lake Baikal ice formation date, duration, and thickness is significantly related to winter temperatures over a wide area from the Caspian Sea to the Pacific and from northern India to the Kara Sea off the northern coast of Siberia. Thus, Lake Baikal ice cover is a robust indicator of continental-scale winter climate. Correlation and composite analysis of surface and upper-atmospheric fields reveal that interannual variability in ice cover is associated with a tripolar pattern of upper-level ge...

Ice cover variability in the Caspian and Aral seas from active and passive microwave satellite data

The paper discusses time and space variations of ice extent in the Caspian and Aral seas during the last decade (1992–2002). It uses synergy of data from active (radar altimeter) and passive (radiometer) microwave nadirlooking instruments onboard the TOPEX/Poseidon satellite. The proposed approach is substantiated and validated using both in situ and satellite imagery data for the Caspian Sea. The results indicate significant spatial and temporal variability of ice conditions, with a significant decrease of both the duration of ice season and ice extent during the last four winters (1998–2002). The TOPEX/Poseidon-derived time series of sea ice extent are very valuable in view of the fragmentary and mostly unpublished data on ice conditions on the Caspian and Aral seas since the mid-1980s.

The use of Satellite Imagery in Investigating the Dynamics of the Ice and Snow Cover Lake Baikal

The generation and sample applications of a set of multispectral remotely sensed products for investigations of Lake Baikal's ice cover variability are described. During the period from mid-January to the end of April, the lake is completely covered with ice, and by analyzing satellite information it is possible to investigate in detail the distribution and dynamics of the main types of snow and ice cover. Different ice cover classes and unfrozen water distributions are estimated from calibrated and navigated NOAA AVHRR 1.1-km imagery of Lake Baikal for January 1994 through May 1999. The processing strategy and characteristics of the products are reviewed. The utility of this type of multiparameter dataset for modelling applications and process studies is discussed. ERS SAR and Resurs images are used for detailed representation of different ice classes distributions.

Ice cover variability in the Caspian and Aral seas from active and passive microwave satellite data

Ice cover variability in the Caspian and Aral seas from active and passive microwave satellite data

A predator's perspective on causal links between climate change, physical forcing and ecosystem response

The mechanisms by which variability in sea ice cover and its effects on the demography of the Antarctic krill Euphausia superba cascade to other ecosystem components such as apex preda- tors remain poorly understood at all spatial and temporal scales, yet these interactions are essential for understanding causal links between climate change, ecosystem response and resource monitor- ing and management in the Southern Ocean. To address some of these issues, we examined the long- term foraging responses of Adelie penguins Pygoscelis adeliae near Palmer Station, western Antarc- tic Peninsula, in relation to ice-induced changes in krill recruitment and availability. Our results suggest that (1) there is a direct, causal relationship between variability in ice cover, krill recruitment, prey availability and predator foraging ecology, (2) regional patterns and trends detected in this study are consistent with similar observations in areas as far north as South Georgia, and (3) large- scale forcing associated with the Antarctic Circumpolar Wave may be governing ecological inter- actions between ice, krill and their predators in the western Antarctic Peninsula and Scotia Sea regions. Another implication of our analyses is that during the last 2 decades in particular, krill pop- ulations have been sustained by strong age classes that emerge episodically every 4 to 5 yr. This raises the possibility that cohort senescence has become an additional ecosystem stressor in an envi- ronment where ice conditions conducive to good krill recruitment are deteriorating due to climate warming. In exploring these interactions, our results suggest that at least 1 'senescence event' has already occurred in the western Antarctic Peninsula region, and it accounts for significant coherent decreases in krill abundance, predator populations and predator foraging and breeding perfor- mance. We propose that krill longevity should be incorporated into models that seek to identify and understand causal links between climate change, physical forcing and ecosystem response in the western Antarctic Peninsula region.

Oceanography of the Canadian Shelf of the Beaufort Sea: A Setting for Marine Life

Conservation of marine biodiversity in the Beaufort Sea demands that we understand what individual organisms require of their physical and geochemical environments in order to survive. Specifically, how do the extraordinary spatial and seasonal variations in ice cover, temperature, light, freshwater, turbidity, and currents of the Beaufort Sea define unique places or times critical to marine life? We start with the traditional "bottom-up" approach, which is to review the strongly seasonal physical forcing of the system, and from it to infer the resultant oceanographic regimes and seasons. This approach, while valuable, remains incomplete: this is due partly to limitations of the data and partly to our limited understanding of this complex system. The oceanographic features (e.g., upwelling regions, recurrent polynyas, coastal currents, sediment types and distributions) define the backdrop that animals "know and understand" in the sense of interacting with one another and finding food and habitat. We therefore seek clues to the underlying oceanographic processes in the behavioural patterns of fish, marine mammals, and birds. This "top-down" approach also has limitations, but it offers the opportunity to seek those connections in the system where climate change is likely to have its greatest impact on biological populations.