Skip to main content
Advanced Search

Filters: Contacts: Jeff Adams (X)

12 results (102ms)   

Filters
Date Range
Extensions
Types
Contacts
Categories
Tag Types
Tag Schemes
View Results as: JSON ATOM CSV
thumbnail
In Arctic ecosystems, freshwater fish migrate seasonally between productive shallow water habitats that freeze in winter and deep overwinter refuge in rivers and lakes. How these movements relate to seasonal hydrology is not well understood. We used passive integrated transponder tags and stream wide antennae to track 1035 Arctic grayling in Crea Creek, a seasonally flowing beaded stream on the Arctic Coastal Plain, Alaska. Migration of juvenile and adult fish into Crea Creek peaked in June immediately after ice break-up in the stream. Fish that entered the stream during periods of high flow and cold stream temperature traveled farther upstream than those entering during periods of lower flow and warmer temperature....
thumbnail
Interactions and feedbacks between abundant surface waters and permafrost fundamentally shapelowland Arctic landscapes. Sublake permafrost is maintained when the maximum ice thickness (MIT) exceedslake depth and mean annual bed temperatures (MABTs) remain below freezing. However, decliningMIT since the1970s is likely causing talik development below shallow lakes. Here we show high-temperature sensitivity towinter ice growth at the water-sediment interface of shallow lakes based on year-round lake sensor data.Empirical model experiments suggest that shallow (1m depth) lakes have warmed substantially over the last30years (2.4°C), withMABT above freezing5 of the last 7years.This is incomparison to slower ratesofwarming...
This project provides a better understanding how linkages among surface-water availability, connectivity, and temperature mediate habitat and trophic dynamics of the Fish Creek Watershed (FCW). These interrelated processes form a shifting mosaic of freshwater habitats across the landscape that can be classified, mapped, understood, and modeled in response to past and future climate and land-use change in a spatial and temporal context. Developing scenarios of freshwater habitat change in this context provides managers and scientists with a flexible template to evaluate a range of potential responses to climate and land-use change. Applying this approach in the FCW is made feasible because of the availability of...
thumbnail
Lakes are dominant and diverse landscapefeatures in the Arctic, but conventional land coverclassification schemes typically map them as a singleuniform class. Here, we present a detailed lake-centricgeospatial database for an Arctic watershed in northernAlaska. We developed a GIS dataset consisting of 4362lakes that provides information on lake morphometry,hydrologic connectivity, surface area dynamics,surrounding terrestrial ecotypes, and other importantconditions describing Arctic lakes. Analyzing thegeospatial database relative to fish and bird survey datashows relations to lake depth and hydrologic connectivity,which are being used to guide research and aid in themanagement of aquatic resources in the NationalPetroleum...
thumbnail
Beaded streams are widespread in permafrost regionsand are considered a common thermokarst landform.However, little is known about their distribution, how andunder what conditions they form, and how their intriguingmorphology translates to ecosystem functions and habitat.Here we report on a circum-Arctic survey of beaded streamsand a watershed-scale analysis in northern Alaska using remotesensing and field studies.We mapped over 400 channelnetworks with beaded morphology throughout the continuouspermafrost zone of northern Alaska, Canada, and Russiaand found the highest abundance associated with mediumto high ground-ice content permafrost in moderately slopingterrain. In one Arctic coastal plain watershed, beaded...
thumbnail
Lakes are prevalent in the Arctic and thus play a key role in regional hydrology. Since manyArctic lakes are shallow and ice grows thick (historically 2 m or greater), seasonal ice commonly freezes tothe lake bed (bedfast ice) by winter’s end. Bedfast ice fundamentally alters lake energy balance and meltoutprocesses compared to deeper lakes that exceed the maximum ice thickness (floating ice) and maintainperennial liquid water below floating ice. Our analysis of lakes in northern Alaska indicated that ice-out ofbedfast ice lakes occurred on average 17 days earlier (22 June) than ice-out on adjacent floating ice lakes (9July). Earlier ice-free conditions in bedfast ice lakes caused higher open-water evaporation,...
thumbnail
Field measurements, satellite observations, and models document a thinning trend in seasonal Arcticlake ice growth, causing a shift from bedfast to floating ice conditions. September sea iceconcentrations in the Arctic Ocean since 1991 correlate well (r=+0.69, p<0.001) to this lakeregime shift. To understand how and to what extent sea ice affects lakes, we conducted modelexperiments to simulate winters with years of high (1991/92) and low (2007/08) sea ice extent forwhich we also had field measurements and satellite imagery characterizing lake ice conditions. Alakeice growth model forced with Weather Research and Forecasting model output produced a 7%decrease in lake ice growth when 2007/08 sea ice was imposed on...
thumbnail
Numerous studies utilizing remote sensing imagery and other methods have documented that thermokarst lakes are undergoing varied hydrological transitions in response to recent climate changes, from surface area expansion to drainage and evaporative desiccation. Here, we provide a synthesis of hydrological conditions for 376 lakes of mainly thermokarst origin across high-latitude North America. We assemble surface water isotope compositions measured during the past decade at five lake-rich landscapes including Arctic Coastal Plain (Alaska), Yukon Flats (Alaska), Old Crow Flats (Yukon), northwestern Hudson Bay Lowlands (Manitoba), and Nunavik (Quebec). These landscapes represent the broad range of thermokarst environments...
thumbnail
In Arctic ecosystems, freshwater fish migrateseasonally between productive shallow water habitatsthat freeze in winter and deep overwinter refuge in riversand lakes. How these movements relate to seasonal hydrologyis not well understood.We used passive integratedtransponder tags and stream wide antennae to track1035 Arctic grayling in Crea Creek, a seasonally flowingbeaded stream on the Arctic Coastal Plain, Alaska. Migrationof juvenile and adult fish into Crea Creek peakedin June immediately after ice break-up in the stream. Fishthat entered the stream during periods of high flow andcold stream temperature traveled farther upstream thanthose entering during periods of lower flow and warmertemperature. We used generalized...
thumbnail
Lake polygons within the Fish Creek Watershed, Alaska were created and classified for a number of variables relevant to size, depth, hydrology, connectivity etc. Products derived from a 5m resolution IfSAR digital surface model by calculating a zero slope. Each feature was expanded by one pixel around the entire perimeter since all waterbodies were truncated by this during the slope calculation. Lakes >=1ha were manually extracted from the dataset and their perimeters further corrected using 2002 CIR orthophotography.
Categories: Data; Types: Downloadable, Map Service, OGC WFS Layer, OGC WMS Layer, OGC WMS Service, Shapefile; Tags: AQUATIC ECOSYSTEMS, AQUATIC ECOSYSTEMS, Academics & scientific researchers, Arctic Landscape Conservation Cooperative data.gov, BIOSPHERE, All tags...
thumbnail
These data are the result of a geospatial analysis involving multi-year SAR-based lake ice regime classification using sigma-naught backscatter intensity from calibrated space-borne C-band SAR for thousands of lakes in 7 lake districts in Alaska, USA, detailed in Engram et al., (in review). Historically, radar backscatter from space-borne and airborne platforms shows a lower backscatter return from bedfast lake ice and a higher backscatter return from floating ice (where liquid phase water exists under the ice) (Jeffries, Morris, Weeks, & Wakabayashi, 1994; Weeks, 1977). We used a threshold method where the threshold to differentiate floating and bedfast ice regimes was determined for each year from the frequency...
thumbnail
The Fish Creek Watershed encompasses diverse aquatic habitats representative of much of the Arctic Coastal Plain of northern Alaska. Beyond surface water and permafrost responses caused by changes in climate, this landscape is also subject to potential land-use impacts related to petroleum development in the National Petroleum Reserve – Alaska (NPR-A). Thus, this region is an ideal setting to address aquatic habitat questions of longstanding interest to Arctic resource managers, scientists, and other stakeholders. Our multidisciplinary team is focusing on broad hypothesis that surface-water availability, connectivity, and temperature mediate aquatic habitats and trophic dynamics. We are working to understand and...


    map background search result map search result map FishCAFE: Response of an Arctic Freshwater Ecosystem to Climate and Land-use Change Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes Depth, ice thickness, and ice-out timing cause divergent hydrologic responses among Arctic lakes Threshold sensitivity of shallow Arctic lakes and sublake permafrost to changing winter climate A lake-centric geospatial database to guide research and inform management decisions in an Arctic watershed in northern Alaska... Fish CAFE Project Information Handout Arctic sea ice decline contributes to thinning lake ice trend in northern Alaska A synthesis of thermokarst lake water balance in high-latitude regions of North America from isotope tracers Seasonal cues of Arctic grayling movement in a small Arctic stream: the importance of surface water connectivity Lake Ice Regime Classification Fish Creek Watershed Lake Classification FishCAFE: Response of an Arctic Freshwater Ecosystem to Climate and Land-use Change Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes Depth, ice thickness, and ice-out timing cause divergent hydrologic responses among Arctic lakes Threshold sensitivity of shallow Arctic lakes and sublake permafrost to changing winter climate A lake-centric geospatial database to guide research and inform management decisions in an Arctic watershed in northern Alaska... Fish CAFE Project Information Handout Arctic sea ice decline contributes to thinning lake ice trend in northern Alaska A synthesis of thermokarst lake water balance in high-latitude regions of North America from isotope tracers Seasonal cues of Arctic grayling movement in a small Arctic stream: the importance of surface water connectivity Fish Creek Watershed Lake Classification Lake Ice Regime Classification