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3. Complexity revealed in the greening of the Arctic

Author

Myers-Smith, Isla H., Kerby, Jeffrey T., Phoenix, Gareth K., Bjerke, Jarle W., Epstein, Howard E., Assmann, Jakob J., John, Christian, Andreu-Hayles, Laia, Angers-Blondin, Sandra, Beck, Pieter S. A., Berner, Logan T., Bhatt, Uma S., Bjorkman, Anne D., Blok, Daan, Bryn, Anders, Christiansen, Casper T., Cornelissen, J. Hans C., Cunliffe, Andrew M., Elmendorf, Sarah C., Forbes, Bruce C., Goetz, Scott J., Hollister, Robert D., de Jong, Rogier, Loranty, Michael M., Macias-Fauria, Marc, Maseyk, Kadmiel, Normand, Signe, Olofsson, Johan, Parker, Thomas C., Parmentier, Frans-Jan W., Post, Eric, Schaepman-Strub, Gabriela, Stordal, Frode, Sullivan, Patrick F., Thomas, Haydn J. D., Tømmervik, Hans, Treharne, Rachael, Tweedie, Craig E., Walker, Donald A., Wilmking, Martin, and Wipf, Sonja

Published
2020
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8. A framework and toolset for standardizing agroecosystem indicators

Author

McCord, Sarah E., primary, Brehm, Joseph R., additional, Burnett, Sarah H., additional, Dietrich, Chris, additional, Edwards, Brandon, additional, Metz, Loretta J., additional, Hernandez Narvaez, Mariano, additional, Pierson, Fred, additional, Ramirez, Kelly S., additional, Stauffer, Nelson G., additional, Webb, Nicholas P., additional, and Tweedie, Craig E., additional

Published
2022
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12. Understanding the climate impacts on decadal vegetation change in northern Alaska

Author

Harris, Jacob A., primary, Hollister, Robert D., additional, Botting, Timothy F., additional, Tweedie, Craig E., additional, Betway, Katlyn R., additional, May, Jeremy L., additional, Barrett, Robert T.S., additional, Leibig, Jenny A., additional, Christoffersen, Hana L., additional, Vargas, Sergio A., additional, Orejel, Mariana, additional, and Fuson, Tabatha L., additional

Published
2022
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13. The U.S. Arctic observing viewer: a web-mapping application for enhancing environmental observation of the changing Arctic

Author

Manley, William F., Gaylord, Allison G., Kassin, Ari, Cody, Ryan, Copenhaver, Walter A., Dover, Mike, Escarzaga, Stephen M., Font, Ryan, Garcia, Alan E., Habermann, Ted, Lin, David H., Score, Roberta, Villarreal, Sandra, and Tweedie, Craig E.

Subjects
United States. National Science Foundation, United States. National Oceanic and Atmospheric Administration, Online information services -- International economic relations, Arctic research, Online services -- International economic relations, Web applications, Geographic information systems, Data entry, Geospatial data, Information services -- International economic relations, Online information service, Geographic information system, Earth sciences, Regional focus/area studies, International Organization for Standardization, Open Geospatial Consortium
Abstract

ABSTRACT. Although much progress has been made with various Arctic Observing efforts, assessing that progress can be difficult. What data collection efforts are established or underway? Where? By whom? To [...]

Published
2015
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16. Multi-Decadal Changes in Tundra Environments and Ecosystems: Synthesis of the International Polar Year-Back to the Future Project (IPY-BTF)

Author

Callaghan, Terry V., Tweedie, Craig E., Åkerman, Jonas, Andrews, Christopher, Bergstedt, Johan, Butler, Malcolm G., Christensen, Torben R., Cooley, Dorothy, Dahlberg, Ulrika, Danby, Ryan K., Daniëls, Fred J. A., de Molenaar, Johannes G., Dick, Jan, Mortensen, Christian Ebbe, Ebert-May, Diane, Emanuelsson, Urban, Eriksson, Håkan, Hedenås, Henrik, Henry, Greg. H. R., Hik, David S., Hobbie, John E., Jantze, Elin J., Jaspers, Cornelia, Johansson, Cecilia, Johansson, Margareta, Johnson, David R., Johnstone, Jill F., Jonasson, Christer, Kennedy, Catherine, Kenney, Alice J., Keuper, Frida, Koh, Saewan, Krebs, Charles J., Lantuit, Hugues, Lara, Mark J., Lin, David, Lougheed, Vanessa L., Madsen, Jesper, Matveyeva, Nadya, McEwen, Daniel C., Myers-Smith, Isla H., Narozhniy, Yuriy K., Olsson, Håkan, Pohjola, Veijo A., Price, Larry W., Rigét, Frank, Rundqvist, Sara, Sandström, Anneli, Tamstorf, Mikkel, Van Bogaert, Rik, Villarreal, Sandra, Webber, Patrick J., and Zemtsov, Valeriy A.

Published
2011
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21. Plant Community Responses to Experimental Warming across the Tundra Biome

Author

Walker, Marilyn D., Wahren, C. Henrik, Hollister, Robert D., Henry, Greg H. R., Ahlquist, Lorraine E., Alatalo, Juha M., Bret-Harte, M. Syndonia, Calef, Monika P., Callaghan, Terry V., Carroll, Amy B., Epstein, Howard E., Jónsdóttir, Ingibjörg S., Klein, Julia A., Magnússon, Borgþór, Molau, Ulf, Oberbauer, Steven F., Rewa, Steven P., Robinson, Clare H., Shaver, Gaius R., Suding, Katharine N., Thompson, Catharine C., Tolvanen, Anne, Totland, Ørjan, Turner, P. Lee, Tweedie, Craig E., Webber, Patrick J., and Wookey, Philip A.

Published
2006
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22. Spatial and Temporal Variation in Primary Productivity (NDVI) of Coastal Alaskan Tundra: Decreased Vegetation Growth Following Earlier Snowmelt

Author

Gamon, John A, Huemmrich, K. Fred, Stone, Robert S, and Tweedie, Craig E

Subjects
Meteorology And Climatology
Abstract

In the Arctic, earlier snowmelt and longer growing seasons due to warming have been hypothesized to increase vegetation productivity. Using the Normalized Difference Vegetation Index (NDVI) from both field and satellite measurements as an indicator of vegetation phenology and productivity, we monitored spatial and temporal patterns of vegetation growth for a coastal wet sedge tundra site near Barrow, Alaska over three growing seasons (2000-2002). Contrary to expectation, earlier snowmelt did not lead to increased productivity. Instead, productivity was associated primarily with precipitation and soil moisture, and secondarily with growing degree days, which, during this period, led to reduced growth in years with earlier snowmelt. Additional moisture effects on productivity and species distribution, operating over a longer time scale, were evident in spatial NDVI patterns associated with microtopography. Lower, wetter regions dominated by graminoids were more productive than higher, drier locations having a higher percentage of lichens and mosses, despite the earlier snowmelt at the more elevated sites. These results call into question the oft-stated hypothesis that earlier arctic growing seasons will lead to greater vegetation productivity. Rather, they agree with an emerging body of evidence from recent field studies indicating that early-season, local environmental conditions, notably moisture and temperature, are primary factors determining arctic vegetation productivity. For this coastal arctic site, early growing season conditions are strongly influenced by microtopography, hydrology, and regional sea ice dynamics, and may not be easily predicted from snowmelt date or seasonal average air temperatures alone. Our comparison of field to satellite NDVI also highlights the value of in-situ monitoring of actual vegetation responses using field optical sampling to obtain detailed information on surface conditions not possible from satellite observations alone.

Published
2015
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23. An emerging international network focused on permafrost coastal systems in transition

Author

Jones, Benjamin M., Tweedie, Craig E., Xiao, Ming, Alexeev, V. A., Baranskaya, Alisa, Belova, N., Bristol, Emily, Bull, Diana L., Guangqing, Chi, Dallimore, Scott, Erikson, Li H., Farquharson, Louise M., Flanary, Chris, Frederick, Jennifer, Fuchs, Matthias, Gibbs, Ann, Graybill, Jessica, Grigoriev, Mikhail N., Grosse, Guido, Günther, Frank, Halvorsen, Kathleen E., Isaev, Vladimir, Irrgang, Anna, Iwahana, Go, Jensen, Anne M., Jones, Craig Alexander, Kanevskiy, Mikhail, Kasper, Jeremy, Kinsman, Nicole, Kokin, Osip, Kroon, Aart, Lantuit, Hugues, Lantz, Trevor C., Liljedahl, Anna K., Lubbad, Raed, Maio, Christopher, Maslakov, Alexey, McClelland, James W, Mota, Alejandro, Nitze, Ingmar, Novikova, Anna V., Ogorodov, Stanislav A., Overbeck, J., Overduin, Pier Paul, Petrov, Andrey N., Richmond, Bruce, Romanovsky, Vladimir E., Rowland, Joel, Sachs, Torsten, Schuur, Edward. A. G., Shabanova, Natalya N., Sinitsyn, Anatoly, Shiklomanov, Nikolay, Streletskiy, Dmitry, Strzelecki, Matt C., Swanson, David, and Thomas, Matthew A.

Abstract

Perennially frozen ground and sea ice are key constituents of permafrost coastal systems, and their presence is the primary difference between temperate and high-latitude coastal processes. These systems are some of the most rapidly changing landscapes on Earth and, in the Arctic, are representative of the challenges being faced at the intersection between natural and anthropogenic systems. Permafrost thaw, in combination with increasing sea level and decreasing sea-ice cover, exposes arctic coastal and nearshore areas to rapid environmental and social changes. Based on decadal timescales, observations in the Arctic indicate an increase in permafrost coastal bluff erosion and storm surge flooding of low-lying ice-rich permafrost terrain. However, circum-arctic observations remain limited and the factors responsible for the apparent increase in arctic coastal dynamics are poorly constrained. A better understanding of permafrost coastal systems and how they are responding to changes in the Arctic is important since a high proportion of Arctic residents live on or near coastlines, and many derive their livelihood from terrestrial and nearshore marine resources. An expanding industrial, scientific, and commercial presence in the Arctic Ocean will also require advanced knowledge about permafrost coastlines as terrestrial access points. Since the issues involved span political, cultural, geographical, and disciplinary borders, an international network focused on permafrost coastal systems in transition is needed. An integrative network focused on permafrost coastal systems is required to realize and address the scale and complexity of the processes, dynamics, and responses of this system to physical, ecological, and social change. A primary focus of such an effort would be guided by the fact that the issues and impacts associated with permafrost coastal systems in transition are far greater than any single institution or discipline is capable of addressing alone. Future permafrost coastal system dynamics will challenge conventional wisdom as the system enters a new state impacting human decision making and adaptation planning, cultural heritage resources and ecosystems, and likely resulting in unforeseen challenges across the Arctic.

Published
2019

24. Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions

Author

Hinzman, Larry D., Bettez, Neil D., Bolton, W. Robert, Chapin, F. Stuart, Dyurgerov, Mark B., Fastie, Chris L., Griffith, Brad, Hollister, Robert D., Hope, Allen, Huntington, Henry P., Jensen, Anne M., Jia, Gensuo J., Jorgenson, Torre, Kane, Douglas L., Klein, David R., Kofinas, Gary, Lynch, Amanda H., Lloyd, Andrea H., McGuire, A. David, Nelson, Frederick E., Oechel, Walter C., Osterkamp, Thomas E., Racine, Charles H., Romanovsky, Vladimir E., Stone, Robert S., Stow, Douglas A., Sturm, Matthew, Tweedie, Craig E., Vourlitis, George L., Walker, Marilyn D., Walker, Donald A., Webber, Patrick J., Welker, Jeffrey M., Winker, Kevin S., and Yoshikawa, Kenji

Published
2005
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26. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

Author

Huemmrich, Karl Fred, Gamon, John A, Tweedie, Craig E, Campbell, Petya K. Entcheva, Landis, David R, and Middleton, Elizabeth M

Subjects
Earth Resources And Remote Sensing
Abstract

Non-vascular plants (lichens and mosses) are significant components of tundra landscapes and may respond to climate change differently from vascular plants affecting ecosystem carbon balance. Remote sensing provides critical tools for monitoring plant cover types, as optical signals provide a way to scale from plot measurements to regional estimates of biophysical properties, for which spatial-temporal patterns may be analyzed. Gas exchange measurements were collected for pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow, AK. These functional types were found to have three significantly different values of light use efficiency (LUE) with values of 0.013 plus or minus 0.0002, 0.0018 plus or minus 0.0002, and 0.0012 plus or minus 0.0001 mol C mol (exp -1) absorbed quanta for vascular plants, mosses and lichens, respectively. Discriminant analysis of the spectra reflectance of these patches identified five spectral bands that separated each of these vegetation functional types as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals. Along the transect, area-averaged canopy LUE estimated from coverage fractions of the three functional types varied widely, even over short distances. The patch-level statistical discriminant functions applied to in situ hyperspectral reflectance data collected along the transect successfully unmixed cover fractions of the vegetation functional types. The unmixing functions, developed from the transect data, were applied to 30 m spatial resolution Earth Observing-1 Hyperion imaging spectrometer data to examine variability in distribution of the vegetation functional types for an area near Barrow, AK. Spatial variability of LUE was derived from the observed functional type distributions. Across this landscape, a fivefold variation in tundra LUE was observed. LUE calculated from the functional type cover fractions was also correlated to a spectral vegetation index developed to detect vegetation chlorophyll content. The concurrence of these alternate methods suggest that hyperspectral remote sensing can distinguish functionally distinct vegetation types and can be used to develop regional estimates of photosynthetic LUE in tundra landscapes.

Published
2013
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30. Engaging Fishers' Ecological Knowledge for Endangered Species Conservation: Four Advantages to Emphasizing Voice in Participatory Action Research

Author

Wedemeyer-Strombel, Kathryn R., primary, Peterson, Markus J., additional, Sanchez, Ramon Neftali, additional, Chavarría, Sofía, additional, Valle, Melissa, additional, Altamirano, Eduardo, additional, Gadea, Velkiss, additional, Sowards, Stacey K., additional, Tweedie, Craig E., additional, and Liles, Michael J., additional

Published
2019
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35. State of the Climate in 2010

Author

Achberger, Christine, Ackerman, Steven A., Ahlstrom, A., Alfaro, Eric J., Allan, Robert J., Alves, Robert J., Amador, Jorge A., Amelie, Vincent, Andrianjafinirina, Solonomenjanahary, Antonov, John, Arndt, Derek S., Ashik, Igor, Atheru, Zachary, Attaher, Samar M., Baez, Julian, Banzon, Viva, Baringer, Molly O., Barreira, Sandra, Barriopedro, David, Barthia, Pawan K., Beal, Lisa M., Becker, Andreas, Behrenfeld, Michael J., Bell, Gerald D., Belward, Alan S., Benedetti, Angela, Berrisford, Paul, Berry, David I., Beszczynska-Moeller, Agnieszka, Bhatt, Uma S., Bidegain, Mario, Bindoff, Nathaniel L., Bissolli, Peter, Blake, Eric S., Blunden, Jessica, Booneeady, Prithiviraj, Bosilovich, Michael G., Boudet, Dagne R., Box, Jason E., Boyer, Timothy P., Bromwich, David H., Brown, Ross, Bryden, Harry L., Bulygina, Olga N., Burrows, John, Butler, J., Cais, Philippe, Calderon, Blanca, Callaghan, T. V., Camargo, Suzana J., Cappelen, John, Carmack, Eddy, Chambers, Don P., Chelliah, Muthuvel, Chidichimo, Maria P., Christiansen, H., Christy, John, Coehlo, Caio A. S., Colwell, Steve, Comiso, Josefino C., Compo, Gilber P., Crouch, Jake, Cunningham, Stuart A., Cutie, Virgen C., Dai, Aiguo, Davydova-Belitskaya, Valentina, Jeu, Richard, Decker, David, Dee, Dick, Demircan, M., Derksen, Chris, Diamond, Howard J., Dlugokencky, Howard, Dohan, Kathleen, Dolman, A. Johannes, Dorigo, Wouter, Drozdov, Dmitry S., Durack, Paul J., Dutton, Geoffrey S., Easterling, David, Ebita, Ayataka, Eischeid, Jon, Elkins, James W., Epstein, Howard E., Euscategui, Christian, Faijka-Williams, Eleanor, Famiglietti, James S., Faniriantsoa, Rija, Feely, Richard A., Fekete, Balazs M., Fenimore, Chris, Fettweis, Xavier, Field, Eric, Fioletov, Vitali E., Fogarty, Vitali E., Fogt, Ryan L., Forbes, B. C., Foster, Michael J., Frajka-Williams, E., Free, Melissa, Frolov, Ivan, Ganesan, A. L., Ganter, Catherine, Gibney, Ethan J., Gill, Stephen, Gill, M., Gitau, Wilson, Gleason, Karin L., Gobron, Nadine, Goldenberg, Stanley B., Goni, Gustavo J., Gonzalez, Idelmis G., Good, Simon A., Gottschalck, Jonathan, Gould, William A., Gouveia, Celia M., Griffiths, Georgina M., Guard, Chip, Guevara, Vladimir V., Haas, C., Hall, Bradley D., Halpert, Michael S., Heidinger, Andrew K., Heil, A., Heim, Richard R., Hennon, Paula A., Henry, Greg H. R., Hidalgo, Hugo G., Hilburn, Kyle, Hirschi, Joel J. M., Ho, Shu-Peng, Hobgood, Jay S., Hoerling, Martin, Holgate, Simon, Hook, Simon J., Hugony, Sebastien, Hurst, D., Ishihara, Hiroshi, Itoh, M., Jaimes, Ena, Jeffries, Martin, Jia, Gensu J., Jin, Xiangze, John, William E., Johnson, Bryan, Johnson, Gregory C., Jones, Philip D., Jumaux, Guillaume, Kabidi, Khadija, Kaiser, Johannes W., Kanzow, Torsten O., Kaplan, Alexey, Kearns, Edward J., Keller, Linda M., Kennedy, John J., Khatiwala, Samar, Kholodov, Alexander, Khoshkam, Mahbobeh, Kikuchi, T., Kimberlain, Todd B., Knaff, John A., Kobayashi, Shinya, Kokelj, Steve V., Korshunova, Natalia N., Kratz, David P., Krishfield, Richard, Kruger, Andries, Kruk, Michael C., Kumar Arun, Lammers, Richard B., Lander, Mark A., Landsea, Chris W., Lantuit, Hugues, Lantz, Trevor C., Lapinel, Braulio P., Lareef, Zubair, Lazzara, Matthew A., Leon, Antonia L., Leon, Gloria, Lauliette, Eric, Levitus, Sydney, Levy, Joel M., L Heureux, Michelle, Lin, I. I., Liu, Hongxing, Liu, Yanju, Liu, Yi, Loeb, Norman G., Long, Craig S., Lorrey, Andrew M., Lumpkin, Rick, Luo, Jing-Jia, Lyman, John M., Macdonald, Alison M., Maddux, Brent C., Maier, Frank, Malkova, Galina, Marchenko, Sergey, Marengo, Jose A., Maritorena, Stephane, Marotzke, Jochem, Martinez Guingla, Rodney, Maslanik, Jochem, Masson, Robert A., Mcbride, Charlotte, Mcgree, Simon, Mclaughlin, Fiona, Mcpeters, Rich, Mcvicar, Tim R., Mears, Carl A., Medany, Mahmoud A., Meier, Walt, Meinen, Christopher S., Merrifield, Mark A., Miller, Laury, Mitchum, Gary T., Montzka, Steve, Morcrette, Jean-Jacques, Mote, Thomas, Muhle, Jens, Mullan, A. Brett, Murray, Don, Nash, Eric R., Nerem, Steven R., Newman, Paul A., Nishino, S., Njau, Leonard, Noetzli, J., Oberbauer, S. F., Oberman, Naum, Obregon, Andre, Ogallo, Laban, Oludhe, Christopher, O Malley, Robert T., Overland, James, Park, Geun-Ha, Parker, David E., Pasch, Richard J., Pegion, Phil, Peltier, Alexandre, Pelto, Mauri S., Penalba, Olga C., Perez, Ramon S., Perlwitz, Judith, Perovich, Donald, Peterson, Thomas C., Pezza, Alexandre B., Phillips, David, Pinzon, Jorge E., Pitts, Michael C., Proshutinsky, A., Quegan, S., Quintana, Juan, Quintero, Alexander, Rabe, B., Rahimzadeh, Fatemeh, Rajeevan, Madhavan, Rayner, Darren, Rayner, Nick A., Raynolds, Martha K., Razuvaev, Vyacheslav N., Reagan, James R., Reid, Phillip, Renwick, James A., Revadekar, Jayashree, Reynolds, Richard W., Richter-Menge, Jacqueline, Rignot, Eric, Robinson, David A., Rodell, Matthew, Rogers, Mark, Romanovsky, Vladimir, Romero-Cruz, Fernando, Ronchail, Josyane, Rosenlof, Karen, Rossi, Shawn, Rutledge, Glenn, Saatchi, Sassan, Sabine, Christopher L., Saha, Suranjana, Sanchez-Lugo, Ahira, Santee, Michelle L., Sato, Hitoshi, Sawaengphokhai, P., Sayouri, Amal, Scambos, Ted A., Schauer, U., Schemm, Jae, Schmid, Claudia, Schneider, Philipp, Schueller, Dominique, Sensoy, Serhat, Sharp, Martin, Shaver, Gus R., Shiklomanov, Alexander, Shiklomanov, N., Shimada, Koji, Siegel, David A., Simmons, Adrian, Skansi, Maria, Smith, Adam, Smith, Cathy, Smith, S., Smith, Thomas M., Sokolov, Vladimir, Spence, Jacqueline M., Srivastava, Arvind Kumar, Stackhouse, Paul W., Stammerjohn, Sharon, Steele, Mike, Steinbrecht, Wolfgang, Stephenson, Tannecia S., Stolarski, Richard S., Tahani, Lloyd, Takahashi, Taro, Taylor, Michael A., Thepaut, Jean-Noel, Thiaw, Wassila M., Thorne, Peter W., Timmermans, M. L., Tobin, Skie, Toole, John, Trewin, Blair C., Trigo, Ricardo M., Tucker, Compton J., Tweedie, Craig E., As, D., Wal, R. S. W., A, Ronald J., Werf, G. R., Vautard, Robert, Vieira, G., Vincent, Lucie A., Vinther, Lucie A., Vinther, B., Vose, Russell, Wagner, Wolfgang, Wahr, John, Walker, David A., Walsh, John, Wang, Chunzai, Wang, Junhong, Wang, Lei, Wang, Muyin, Wang, Sheng-Hung, Wanninkhof, Rik, Weaver, Scott, Webber, Patrick J., Weber, Mark, Weller, Robert A., Weyman, James, Whitewood, Robert, Wijffels, Susan E., Wilber, Anne C., Willett, Katharine M., Williams, W., Willis, Joshua K., Wolken, Gabriel, Wong, Takmeng, Woodgate, Rebecca, Woodworth, Philip, Wovrosh, Alex J., Xue, Yan, Michiyo Yamamoto-Kawai, Yin, Xungang, Yu, Lisan, Zhang, Liangying, Zhang, Peiqun, Zhao, L., Zhou, Xinjia, and Zimmermann, S.

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, 13. Climate action, Earth science, Environmental science, Thermal state, 14. Life underwater, 010502 geochemistry & geophysics, 16. Peace & justice, Permafrost, 01 natural sciences, 0105 earth and related environmental sciences
Abstract

Several large-scale climate patterns influenced climate conditions and weather patterns across the globe during 2010. The transition from a warm El Niño phase at the beginning of the year to a cool La Niña phase by July contributed to many notable events, ranging from record wetness across much of Australia to historically low Eastern Pacific basin and near-record high North Atlantic basin hurricane activity. The remaining five main hurricane basins experienced below- to well-below-normal tropical cyclone activity. The negative phase of the Arctic Oscillation was a major driver of Northern Hemisphere temperature patterns during 2009/10 winter and again in late 2010. It contributed to record snowfall and unusually low temperatures over much of northern Eurasia and parts of the United States, while bringing above-normal temperatures to the high northern latitudes. The February Arctic Oscillation Index value was the most negative since records began in 1950. The 2010 average global land and ocean surface temperature was among the two warmest years on record. The Arctic continued to warm at about twice the rate of lower latitudes. The eastern and tropical Pacific Ocean cooled about 1°C from 2009 to 2010, reflecting the transition from the 2009/10 El Niño to the 2010/11 La Niña. Ocean heat fluxes contributed to warm sea surface temperature anomalies in the North Atlantic and the tropical Indian and western Pacific Oceans. Global integrals of upper ocean heat content for the past several years have reached values consistently higher than for all prior times in the record, demonstrating the dominant role of the ocean in the Earth's energy budget. Deep and abyssal waters of Antarctic origin have also trended warmer on average since the early 1990s. Lower tropospheric temperatures typically lag ENSO surface fluctuations by two to four months, thus the 2010 temperature was dominated by the warm phase El Niño conditions that occurred during the latter half of 2009 and early 2010 and was second warmest on record. The stratosphere continued to be anomalously cool. Annual global precipitation over land areas was about five percent above normal. Precipitation over the ocean was drier than normal after a wet year in 2009. Overall, saltier (higher evaporation) regions of the ocean surface continue to be anomalously salty, and fresher (higher precipitation) regions continue to be anomalously fresh. This salinity pattern, which has held since at least 2004, suggests an increase in the hydrological cycle. Sea ice conditions in the Arctic were significantly different than those in the Antarctic during the year. The annual minimum ice extent in the Arctic—reached in September—was the third lowest on record since 1979. In the Antarctic, zonally averaged sea ice extent reached an all-time record maximum from mid-June through late August and again from mid-November through early December. Corresponding record positive Southern Hemisphere Annular Mode Indices influenced the Antarctic sea ice extents. Greenland glaciers lost more mass than any other year in the decade-long record. The Greenland Ice Sheet lost a record amount of mass, as the melt rate was the highest since at least 1958, and the area and duration of the melting was greater than any year since at least 1978. High summer air temperatures and a longer melt season also caused a continued increase in the rate of ice mass loss from small glaciers and ice caps in the Canadian Arctic. Coastal sites in Alaska show continuous permafrost warming and sites in Alaska, Canada, and Russia indicate more significant warming in relatively cold permafrost than in warm permafrost in the same geographical area. With regional differences, permafrost temperatures are now up to 2°C warmer than they were 20 to 30 years ago. Preliminary data indicate there is a high probability that 2010 will be the 20th consecutive year that alpine glaciers have lost mass. Atmospheric greenhouse gas concentrations continued to rise and ozone depleting substances continued to decrease. Carbon dioxide increased by 2.60 ppm in 2010, a rate above both the 2009 and the 1980–2010 average rates. The global ocean carbon dioxide uptake for the 2009 transition period from La Niña to El Niño conditions, the most recent period for which analyzed data are available, is estimated to be similar to the long-term average. The 2010 Antarctic ozone hole was among the lowest 20% compared with other years since 1990, a result of warmer-than-average temperatures in the Antarctic stratosphere during austral winter between mid-July and early September.

Published
2011
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38. Nutrient Release From Permafrost Thaw Enhances CH4 Emissions From Arctic Tundra Wetlands.

Author

Lara, Mark J., Lougheed, Vanessa L., Tweedie, Craig E., Lin, David H., and Andresen, Christian

Subjects
PERMAFROST, WETLANDS, METHANE, MACROPHYTES, TUNDRAS
Abstract

High‐latitude climate change has impacted vegetation productivity, composition, and distribution across tundra ecosystems. Over the past few decades in northern Alaska, emergent macrophytes have increased in cover and density, coincident with increased air and water temperature, active layer depth, and nutrient availability. Unraveling the covarying climate and environmental controls influencing long‐term change trajectories is paramount for advancing our predictive understanding of the causes and consequences of warming in permafrost ecosystems. Within a climate‐controlled carbon flux monitoring system, we evaluate the impact of elevated nutrient availability associated with degraded permafrost (high‐treatment) and maximum field observations (low‐treatment), on aquatic macrophyte growth and methane (CH4) emissions. Nine aquatic Arctophila fulva‐dominated tundra monoliths were extracted from tundra ponds near Utqiaġvik, Alaska, and placed in growth chambers that controlled ambient conditions (i.e., light, temperature, and water table), while measuring plant growth (periodically) and CH4 fluxes (continuously) for 12 weeks. Results indicate that high nutrient treatments similar to that released from permafrost thaw can increase macrophyte biomass and total CH4 emission by 54 and 64%, respectively. However, low treatments did not respond to fertilization. We estimate that permafrost thaw in tundra wetlands near Utqiaġvik have the potential to enhance regional CH4 efflux by 30%. This study demonstrates the sensitivity of arctic tundra wetland biogeochemistry to nutrient release from permafrost thaw and suggests the decadal‐scale expansion of A. fulva‐dominant aquatic plant communities, and increased CH4 emissions in the region were likely in response to thawing permafrost, potentially representing a novel case study of the permafrost carbon feedback to warming. Plain Language Summary: Over the past half century near the town of Utqiaġvik (formerly Barrow) Alaska, plants growing in wetlands have expanded, over the same time period as increases in air/pond temperatures, permafrost thaw, and nutrient availability. Although circumstantial evidence suggests nutrients released from permafrost thaw may have influenced past vegetation expansion and land‐atmosphere carbon exchange, direct evidence is lacking. We built a climate and environmentally controlled carbon flux monitoring system to evaluate the impact of nutrient availability on plant growth and CH4 emissions, associated with (1) permafrost thaw and (2) the maximum field‐based observations. We found nutrients released from permafrost thaw/degradation to increase emergent plant biomass and CH4 emissions by 54 and 64%, respectively. While, nutrient concentrations similar to maximum field concentrations had no effect. Assuming permafrost thaw only occurs in aquatic tundra (~9% of the land surface area), our estimates suggest that regional CH4 emissions may be enhanced by 30%. We conclude that long‐term patterns of emergent vegetation expansion and increased CH4 emissions in this region were likely due to thawing permafrost, which may represent a novel well‐documented case study of the permafrost carbon feedback to warming. Key Points: Simulating nutrient availability from degraded permafrost increased aquatic macrophyte biomass and CH4 emission 54 and 64%Fertilization similar to field‐based maximums in aquatic tundra had no effect on macrophyte biomass or CH4 emissionsRegional nutrient release from thawing permafrost may increase CH4 emissions in aquatic tundra to 75% of current regional CH4 emissions [ABSTRACT FROM AUTHOR]

Published
2019
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39. The Alaska Arctic Vegetation Archive (AVA-AK)

Author

Walker, Donald A., Breen, Amy L., Druckenmiller, Lisa A., Wirth, Lisa W., Fisher, Will, Raynolds, Martha K., Šibík, Jozef, Walker, Marilyn D., Hennekens, Stephan, Boggs, Keith, Boucher, Tina, Buchhorn, Marcel, Bültmann, Helga, Cooper, David J., Daniëls, Fred J.A., Davidson, Scott J., Ebersole, James J., Elmendorf, Sara C., Epstein, Howard E., Gould, William A., Hollister, Robert D., Iversen, Colleen M., Jorgenson, M.T., Kade, Anja, Lee, Michael T., MacKenzie, William H., Peet, Robert K., Peirce, Jana L., Schickhoff, Udo, Sloan, Victoria L., Talbot, Stephen S., Tweedie, Craig E., Villarreal, Sandra, Webber, Patrick J., Zona, Donatella, Walker, Donald A., Breen, Amy L., Druckenmiller, Lisa A., Wirth, Lisa W., Fisher, Will, Raynolds, Martha K., Šibík, Jozef, Walker, Marilyn D., Hennekens, Stephan, Boggs, Keith, Boucher, Tina, Buchhorn, Marcel, Bültmann, Helga, Cooper, David J., Daniëls, Fred J.A., Davidson, Scott J., Ebersole, James J., Elmendorf, Sara C., Epstein, Howard E., Gould, William A., Hollister, Robert D., Iversen, Colleen M., Jorgenson, M.T., Kade, Anja, Lee, Michael T., MacKenzie, William H., Peet, Robert K., Peirce, Jana L., Schickhoff, Udo, Sloan, Victoria L., Talbot, Stephen S., Tweedie, Craig E., Villarreal, Sandra, Webber, Patrick J., and Zona, Donatella

Abstract

The Alaska Arctic Vegetation Archive (AVA-AK, GIVD-ID: NA-US-014) is a free, publically available database archive of vegetation-plot data from the Arctic tundra region of northern Alaska. The archive currently contains 24 datasets with 3,026 non-overlapping plots. Of these, 74% have geolocation data with 25-m or better precision. Species cover data and header data are stored in a Turboveg database. A standardized Pan Arctic Species List provides a consistent nomenclature for vascular plants, bryophytes, and lichens in the archive. A web-based online Alaska Arctic Geoecological Atlas (AGA-AK) allows viewing and downloading the species data in a variety of formats, and provides access to a wide variety of ancillary data. We conducted a preliminary cluster analysis of the first 16 datasets (1,613 plots) to examine how the spectrum of derived clusters is related to the suite of datasets, habitat types, and environmental gradients. We present the contents of the archive, assess its strengths and weaknesses, and provide three supplementary files that include the data dictionary, a list of habitat types, an overview of the datasets, and details of the cluster analysis.

Published
2016

42. The Alaska Arctic Vegetation Archive (AVA-AK)

Author

Walker, Donald A., primary, Breen, Amy L., additional, Druckenmiller, Lisa A., additional, Wirth, Lisa W., additional, Fisher, Will, additional, Raynolds, Martha K., additional, Šibík, Jozef, additional, Walker, Marilyn D., additional, Hennekens, Stephan, additional, Boggs, Keith, additional, Boucher, Tina, additional, Buchhorn, Marcel, additional, Bültmann, Helga, additional, Cooper, David J., additional, Daniëls, Fred J.A, additional, Davidson, Scott J., additional, Ebersole, James J., additional, Elmendorf, Sara C., additional, Epstein, Howard E., additional, Gould, William A., additional, Hollister, Robert D., additional, Iversen, Colleen M., additional, Jorgenson, M. Torre, additional, Kade, Anja, additional, Lee, Michael T., additional, MacKenzie, William H., additional, Peet, Robert K., additional, Peirce, Jana L., additional, Schickhoff, Udo, additional, Sloan, Victoria L., additional, Talbot, Stephen S., additional, Tweedie, Craig E., additional, Villarreal, Sandra, additional, Webber, Patrick J., additional, and Zona, Donatella, additional

Published
2016
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43. Short-Term Impacts of the Air Temperature on Greening and Senescence in Alaskan Arctic Plant Tundra Habitats.

Author

May, Jeremy L., Healey, Nathan C., Ahrends, Hella E., Hollister, Robert D., Tweedie, Craig E., Welker, Jeffrey M., Gould, William A., and Oberbauer, Steven F.

Subjects
ATMOSPHERIC temperature, TUNDRAS, NORMALIZED difference vegetation index, CLIMATE change, PHENOLOGY
Abstract

Climate change is warming the temperatures and lengthening the Arctic growing season with potentially important effects on plant phenology. The ability of plant species to acclimate to changing climatic conditions will dictate the level to which their spatial coverage and habitat-type dominance is different in the future. While the effect of changes in temperature on phenology and species composition have been observed at the plot and at the regional scale, a systematic assessment at medium spatial scales using new noninvasive sensor techniques has not been performed yet. At four sites across the North Slope of Alaska, changes in the Normalized Difference Vegetation Index (NDVI) signal were observed by Mobile Instrumented Sensor Platforms (MISP) that are suspended over 50 m transects spanning local moisture gradients. The rates of greening (measured in June) and senescence (measured in August) in response to the air temperature was estimated by changes in NDVI measured as the difference between the NDVI on a specific date and three days later. In June, graminoid- and shrub-dominated habitats showed the greatest rates of NDVI increase in response to the high air temperatures, while forb- and lichen-dominated habitats were less responsive. In August, the NDVI was more responsive to variations in the daily average temperature than spring greening at all sites. For graminoid- and shrub-dominated habitats, we observed a delayed decrease of the NDVI, reflecting a prolonged growing season, in response to high August temperatures. Consequently, the annual C assimilation capacity of these habitats is increased, which in turn may be partially responsible for shrub expansion and further increases in net summer CO2 fixation. Strong interannual differences highlight that long-term and noninvasive measurements of such complex feedback mechanisms in arctic ecosystems are critical to fully articulate the net effects of climate variability and climate change on plant community and ecosystem processes. [ABSTRACT FROM AUTHOR]

Published
2017
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44. Nutrient Release From Permafrost Thaw Enhances CH4Emissions From Arctic Tundra Wetlands

Author

Lara, Mark J., Lin, David H., Andresen, Christian, Lougheed, Vanessa L., and Tweedie, Craig E.

Abstract

High‐latitude climate change has impacted vegetation productivity, composition, and distribution across tundra ecosystems. Over the past few decades in northern Alaska, emergent macrophytes have increased in cover and density, coincident with increased air and water temperature, active layer depth, and nutrient availability. Unraveling the covarying climate and environmental controls influencing long‐term change trajectories is paramount for advancing our predictive understanding of the causes and consequences of warming in permafrost ecosystems. Within a climate‐controlled carbon flux monitoring system, we evaluate the impact of elevated nutrient availability associated with degraded permafrost (high‐treatment) and maximum field observations (low‐treatment), on aquatic macrophyte growth and methane (CH4) emissions. Nine aquatic Arctophila fulva‐dominated tundra monoliths were extracted from tundra ponds near Utqiaġvik, Alaska, and placed in growth chambers that controlled ambient conditions (i.e., light, temperature, and water table), while measuring plant growth (periodically) and CH4fluxes (continuously) for 12 weeks. Results indicate that high nutrient treatments similar to that released from permafrost thaw can increase macrophyte biomass and total CH4emission by 54 and 64%, respectively. However, low treatments did not respond to fertilization. We estimate that permafrost thaw in tundra wetlands near Utqiaġvik have the potential to enhance regional CH4efflux by 30%. This study demonstrates the sensitivity of arctic tundra wetland biogeochemistry to nutrient release from permafrost thaw and suggests the decadal‐scale expansion of A. fulva‐dominant aquatic plant communities, and increased CH4emissions in the region were likely in response to thawing permafrost, potentially representing a novel case study of the permafrost carbon feedback to warming. Over the past half century near the town of Utqiaġvik (formerly Barrow) Alaska, plants growing in wetlands have expanded, over the same time period as increases in air/pond temperatures, permafrost thaw, and nutrient availability. Although circumstantial evidence suggests nutrients released from permafrost thaw may have influenced past vegetation expansion and land‐atmosphere carbon exchange, direct evidence is lacking. We built a climate and environmentally controlled carbon flux monitoring system to evaluate the impact of nutrient availability on plant growth and CH4emissions, associated with (1) permafrost thaw and (2) the maximum field‐based observations. We found nutrients released from permafrost thaw/degradation to increase emergent plant biomass and CH4emissions by 54 and 64%, respectively. While, nutrient concentrations similar to maximum field concentrations had no effect. Assuming permafrost thaw only occurs in aquatic tundra (~9% of the land surface area), our estimates suggest that regional CH4emissions may be enhanced by 30%. We conclude that long‐term patterns of emergent vegetation expansion and increased CH4emissions in this region were likely due to thawing permafrost, which may represent a novel well‐documented case study of the permafrost carbon feedback to warming. Simulating nutrient availability from degraded permafrost increased aquatic macrophyte biomass and CH4emission 54 and 64%Fertilization similar to field‐based maximums in aquatic tundra had no effect on macrophyte biomass or CH4emissionsRegional nutrient release from thawing permafrost may increase CH4emissions in aquatic tundra to 75% of current regional CH4emissions

Published
2019
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47. Polygonal tundra geomorphological change in response to warming alters future CO2 and CH4 flux on the Barrow Peninsula

Author

Lara, Mark J., McGuire, A. David, Euskirchen, Eugenie S., Tweedie, Craig E., Hinkel, Kenneth M., Skurikhin, Alexei N., Romanovsky, Vladimir E., Grosse, Guido, Bolton, W. Robert, Genet, Helene, Lara, Mark J., McGuire, A. David, Euskirchen, Eugenie S., Tweedie, Craig E., Hinkel, Kenneth M., Skurikhin, Alexei N., Romanovsky, Vladimir E., Grosse, Guido, Bolton, W. Robert, and Genet, Helene

Abstract

The landscape of the Barrow Peninsula in northern Alaska is thought to have formed over centuries to millennia, and is now dominated by ice-wedge polygonal tundra that spans drained thaw-lake basins and interstitial tundra. In nearby tundra regions, studies have identified a rapid increase in thermokarst formation (i.e., pits) over recent decades in response to climate warming, facilitating changes in polygonal tundra geomorphology. We assessed the future impact of 100 years of tundra geomorphic change on peak growing season carbon exchange in response to: (i) landscape succession associated with the thaw-lake cycle; and (ii) low, moderate, and extreme scenarios of thermokarst pit formation (10%, 30%, and 50%) reported for Alaskan arctic tundra sites. We developed a 30 × 30 m resolution tundra geomorphology map (overall accuracy:75%; Kappa:0.69) for our ~1800 km² study area composed of ten classes; drained slope, high center polygon, flat-center polygon, low center polygon, coalescent low center polygon, polygon trough, meadow, ponds, rivers, and lakes, to determine their spatial distribution across the Barrow Peninsula. Land-atmosphere CO2 and CH4 flux data were collected for the summers of 2006–2010 at eighty-two sites near Barrow, across the mapped classes. The developed geomorphic map was used for the regional assessment of carbon flux. Results indicate (i) at present during peak growing season on the Barrow Peninsula, CO2 uptake occurs at -902.3 106gC-CO2 day−1 (uncertainty using 95% CI is between −438.3 and −1366 106gC-CO2 day−1) and CH4 flux at 28.9 106gC-CH4 day−1(uncertainty using 95% CI is between 12.9 and 44.9 106gC-CH4 day−1), (ii) one century of future landscape change associated with the thaw-lake cycle only slightly alter CO2 and CH4 exchange, while (iii) moderate increases in thermokarst pits would strengthen both CO2 uptake (−166.9 106gC-CO2 day−1) and CH4 flux (2.8 106gC-CH4 day−1) with geomorphic change from low to high center polygons, cumulative

Published
2014

48. Experiment, monitoring, and gradient methods used to infer climate change effects on plant communities yield consistent patterns

Author

Elmendorf, Sarah C., primary, Henry, Gregory H. R., additional, Hollister, Robert D., additional, Fosaa, Anna Maria, additional, Gould, William A., additional, Hermanutz, Luise, additional, Hofgaard, Annika, additional, Jónsdóttir, Ingibjörg S., additional, Jorgenson, Janet C., additional, Lévesque, Esther, additional, Magnusson, Borgþór, additional, Molau, Ulf, additional, Myers-Smith, Isla H., additional, Oberbauer, Steven F., additional, Rixen, Christian, additional, Tweedie, Craig E., additional, and Walker, Marilyn D., additional

Published
2014
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50. Phenocams Bridge the Gap between Field and Satellite Observations in an Arid Grassland Ecosystem.

Author

Browning, Dawn M., Karl, JasonW., Morin, David, Richardson, Andrew D., and Tweedie, Craig E.

Subjects
REMOTE sensing, PLANT growth, LAND cover, NORMALIZED difference vegetation index, PHENOLOGY
Abstract

Near surface (i.e., camera) and satellite remote sensing metrics have become widely used indicators of plant growing seasons. While robust linkages have been established between field metrics and ecosystem exchange in many land cover types, assessment of how well remotely-derived season start and end dates depict field conditions in arid ecosystems remain unknown. We evaluated the correspondence between field measures of start (SOS; leaves unfolded and canopy greenness > 0) and end of season (EOS) and canopy greenness for two widespread species in southwestern U.S. ecosystems with those metrics estimated from near-surface cameras and MODIS NDVI for five years (2012–2016). Using Timesat software to estimate SOS and EOS from the phenocam green chromatic coordinate (GCC) greenness index resulted in good agreement with ground observations for honey mesquite but not black grama. Despite differences in the detectability of SOS and EOS for the two species, GCC was significantly correlated with field estimates of canopy greenness for both species throughout the growing season. MODIS NDVI for this arid grassland site was driven by the black grama signal although a mesquite signal was discernable in average rainfall years. Our findings suggest phenocams could help meet myriad needs in natural resource management. [ABSTRACT FROM AUTHOR]

Published
2017
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