IARC Seminar Series

September 22nd

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Two year-long (2004-05 and 2005-06) records of currents from two moorings deployed at the continental slope of the Laptev Sea (78° 26'N, 125°40'E; ~2690 m) have been used in order to define the properties of tidal currents in the upper 200-m ocean layer. Harmonic and spectral analyses of currents showed that the solar semi-diurnal tidal constituent S2 dominates over the lunar semi-diurnal M2 and diurnal constituents due to resonant interaction of the super-inertial wave with sloping bottom topography. Strong anti-correlation (-0.73 +/-0.05) was found between the upper 50m S2 current amplitudes and local sea-ice concentration, with four-fold (from ~2.0 to 8.5 cm/s) amplification of tidal currents under ice-free conditions. This amplification is probably due to a change of local resonance conditions for the S2 tidal current. Discussed results may be important for understanding the increasing role of tides in a seasonally ice-free Arctic Ocean.

October 20th

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Sea is one of the world’s most productive marine ecosystems, with its fisheries representing half of the marine harvest in United States waters. Large changes in Bering Sea ecosystem dynamics have been observed on inter-annual and inter-decadal time scales, although the mechanisms giving rise to these changes are not well understood. Gibson’s ecosystem modeling work includes development of a lower trophic level ecosystem model for the Bering Sea for exploration of the relationship between climate, ocean conditions, productivity and flow of energy through the food web; as well as the use of a float tracking model to explore the mechanisms, timing and location of on-shelf zooplankton transport under a variety of environmental conditions. Through discussion of these projects, Gibson will introduce the use of Eularian Nutrient-Phytoplankton-Zooplankton type lower trophic level ecosystem model and Lagrangian Individual Based Models as tools to explore and understand marine ecosystem dynamics and provide insights into Eastern Bering Sea ecosystem dynamics.

October 27th

The distribution of trace metals in the Arctic Ocean has implications for their global cycles, yet until recently very limited trace metal data was available from this rapidly changing ocean. International Polar Year (IPY) cruises have provided the first high resolution profiles from the Eurasian basins (Nansen, Amundsen and Makarov in 2007) and from the Canada Basin (in 2009). Additionally, JAMSTEC cruises (2008 and 2010) in the western Arctic Ocean have provided trace metal data from a region in between the waters surveyed by the IPY cruises. Here we present dissolved and particulate trace metal data from samples collected onboard the R/V Mirai during the 2010 JAMSTEC Arctic cruise. Results will be presented in context with newly published Arctic trace metal data. Shelf inputs were apparent at mid depths in the dissolved and the suspended particulate data. Suspended particles offshore had an Fe/Al ratio of 0.56 (r2 = 0.98), a value within the range of previously measured Arctic shelf sediments. This transported sediment contained a high percentage of leachable metals which could potentially contribute to the dissolved metal pools of the basin.

November 10th

The North Atlantic ocean circulation is important for regional and global climate variability and change. In this study, we employed the fully-coupled ocean-atmosphere-sea ice-land model COSMOS and conducted simulations for five historical climate states, including the Eemian (132,000 years ago), stadial Marine Isotope Stage3 (MIS-3, 32,000 years ago), Last Glacial Maximum (LGM, 22-18,000 years ago), Mid Holocene (5-8,000 years ago), and present-day. The simulations aim to describe millennial-scale interglacial/glacial climate states, variability and changes in the late Quaternary. Our present study focuses on the variation of North Atlantic Subtropical Gyre (SPG), Subpolar Gyre (SPG) and Gulf Stream, and we also analyzed surface wind stress curl. We found that the growth of Laurentide and Greenland Ice sheet enhances surface wind and in turn, intensifies glacial surface North Atlantic ocean gyres during the MIS-3 and the LGM. The glacial Gulf Stream is also strengthened as a result of increased sea surface height (SSH) gradient between the SPG and STG. Statistical analysis also indicates that surface wind stress plays a modulating role in the glacial Atlantic Meridional Ocean Circulation (AMOC) variability.

November 23rd

The Next-Generation Ecosystem Experiments (NGEE) project will use observations and models to quantify the response of physical, ecological, and biogeochemical processes to climatic change across molecular to landscape scales. Field and lab research will focus on interactions that drive ecosystem-climate feedbacks through greenhouse gas fluxes and changes in surface energy balance investigated across a hierarchy of scales, including the pore/core, plot, and landscape scales. These feedbacks will arise due to the gradual thawing of permafrost and the thickening of the seasonal active layer. Feedbacks will also occur as a result of the threshold-dominated processes of permafrost degradation and thermokarst formation and through the many processes that are influenced as a result of these landscape-scale dynamics. Our approach will consider how components of complex systems are linked and the interplay in space and time that determines system behavior. The research scope is designed to address our overarching science question through a series of integrated field observations, lab experiments, and modeling activities. Insights gained in the work will be used to address the challenge of extrapolating process studies to larger grid scales of climate models and to sharpen our scientific hypotheses about physical, chemical, and biological processes that shape the structure and function of Arctic ecosystems. Our goal throughout the NGEE project will be to provide the underpinning science and process understanding required to develop a new generation of high-resolution land surface simulation capabilities for the Arctic. Fundamental knowledge gained in these investigations will be used to improve representation of ecosystem dynamics, subsurface biogeochemistry, and land-atmosphere processes in regional and global models, and will reduce uncertainty and improve prediction of climate change in high-latitude ecosystems.

December 1st

For more information on IARC's presence at AGU's Fall Meeting 2011:
http://www.iarc.uaf.edu/spotlights/2011/agu

January 26th

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Analysis of modern and historical observations demonstrates that the temperature of the intermediate-depth (150–900 m) Atlantic water (AW) of the Arctic Ocean has increased since the 1960-70s. The AW warming has been uneven in time; a local ~1oC maximum was observed in the mid-1990s, followed by an intervening minimum and an additional warming that culminated in 2007 with temperatures higher than in the 1990s by 0.24oC.

Observations and modeling results suggest upward spread of AW heat through the Eurasian Basin halocline. For example, modeling experiments suggest that over the last ~50 years there was a loss of 28–35 cm of ice thickness in response to the anomalous heat flux resulted from the increase of the AW temperature. This amount of thinning is comparable to the 29 cm of ice thickness loss due to local atmospheric thermodynamic forcing estimated from observations of fast-ice thickness decline. The implication is that AW warming helped precondition the polar ice cap for the extreme ice loss observed in recent years.

Over the past decade, atmospheric thermodynamic forcing played the increasingly important role in shaping changes of the Arctic multiyear ice (MYI). However, analysis of satellite ice motion suggests that the role of ice export through straits connecting the Arctic Ocean with sub-polar basins may be elusive. Available observations suggest a thermodynamic coupling between the heat of the ocean interior and the sea ice. In the Canadian Basin, the impact of Pacific water warmth has been recently documented. While vertical AW heat fluxes are negligible in the Canadian Basin, turbulent mixing may be strong enough in the western Nansen Basin to produce a sizeable effect of AW heat on sea ice. In the eastern Eurasian Basin, double diffusion provides an important alternative to weak turbulent mixing for upward AW heat transport. The relative roles of dynamic and thermodynamic factors in recent changes of the Arctic MYI cover remains to be determined. Quantifying these roles is a high priority if we are to develop reliable forecasts of the future state of Arctic ice coverage.

February 2nd

The multi-decadal oscillation of period of 50-60 years is a prominent feature of the present climate change (1900-2010), which is superposed on an approximately linear increase of the global temperature increase from 1850 to 2000. The present halting of global average temperature from 2000 to 2011, together with several other changes in permafrost temperature, changes of sea ice in the Arctic Ocean and of sea level, may be due to the present negative phase of the multi-decadal oscillation, despite the fact that CO2 is still rising and thus global warming should have continued. Indeed, a detailed spectral analysis is available, indicating that the linear increase of temperature will be overwhelmed by the multi-decadal oscillation until 2030, namely cooling. It is shown that a similar cooling occurred from 1940 to 1970, despite the fact that CO2 increased rapidly after 1946. The Pacific Decadal Oscillation has a similar phase as that of the multi-decadal oscillation.

February 23rd

Black spruce is one of the most abundant forest types in North America, occupying 44% of Interior Alaska (Viereck et al., 1986). To understand the roles and characteristics of this type of forest in eco-hydrological and micrometeorological processes of a sub-Arctic region, the JAMSTEC-IARC Collaboration Study (JICS) supersite was established in a black spruce forest at the center of a flat basin of the Poker Flat Research Range (PFRR), University of Alaska Fairbanks in 2010. In this site, the 17-m tower was build, and the measurements of the heat, water, and CO2 fluxes and other meteorological components are conducted since October 2010. The supersite will be introduced, and a discussion of the innovations in the measured observations over 2011 will be presented.

March 8th

Characteristics of cloud-base height over the ice-free Arctic during autumn Cloud –base observations with the aid of ceilometer and radiosonde over the ice-free Chukchi and Beaufort Seas during autumn have been conducted since 1999 by　using the Japanese R/V Mirai. Comparison of cloud-base height between ice-free ocean case (from 1999 to 2010) and ice-covered case (SHEBA in 1998) indicates the decrease (increase) of 30 percent in frequency of lower clouds with a ceiling below (above) 500m. Over ice covered, the temperature at troposphere in 1990s was higher than those in 1980s. In ice-free case (2000s), the highest temperature was clearly at near surface. It indicate that upward turbulent heat flux is increasing from ocean due to recent sea-ice retreat.

March 23rd

Globally, large uncertainties exist in estimates of lake and wetland methane emissions, in part due to the spatial and temporal heterogeneity of per-unit-area emissions rates and to the difficulty of measuring their contributing areas at large scales. Here we use a hybrid bottom-up and top-down approach, involving a coupled land-atmosphere modeling framework and both in situ and remote sensing observations, to bracket the ranges of possible contributing areas and emissions rates from lakes and wetlands in West Siberia. Our modeling framework consists of the Variable Infiltration Capacity (VIC) land surface model extended to handle carbon cycling and wetland methane emissions, coupled to the National Institute for Environmental Studies atmospheric transport and chemistry (ACTM) model. Remote sensing observations include the active/passive microwave (QuikSCAT/AMSR-E) inundation product of Schroeder et al. (2010), Synthetic Aperture Radar (PALSAR) classifications of open water and saturated soil, and atmospheric methane concentrations from the AIRS satellite sensor. We employ a Bayesian statistical approach to assess and constrain the likely ranges of parameter values such as: the areal extents of lakes, wetland inundation, and saturated soil; and lake and wetland methane emissions rates. Different combinations of lake and wetland areas and emission rates result in markedly different spatial patterns emissions across West Siberia. When these emissions are ingested by ACTM, the resulting spatial patterns of methane concentrations can be compared to AIRS retrievals to assess the likelihood of the different lake areas and emissions rates. Preliminary results indicate that lake areas inferred from active/passive microwave are more likely than those from the Global Lake and Wetland Database, and that lake emissions rates across West Siberia are likely near the high end of the range reported in the literature.

April 5th

During my last 50 years of research, I have learned many things the hard way. I have summarized these experiences in 10 lessons for younger researchers. Since my work has tended to deviate from the conventional beliefs of most contemporary researchers, I have needed to support my positions with additional research. I hope these lessons are of practical use. Although this talk is based on my own experience in geophysics, no background other than undergraduate science is necessary. I hope my talk will be informative as well as entertaining.

April 19th

• Ipshita Majhi: Uncertainties in Arctic Precipitation
• Chas Jones: Using local knowledge, hydrology, and climate scenarios to develop a driftwood harvest model in Interior Alaska
• Tereza Bendelova: Investigations of thermal regimes of Arctic lakes near Kotzebue, Alaska
• Katrina Bennett: Spring Snowmelt Dynamics in Interior Alaskan Watersheds for the Recent Decade (2001-2011)

May 3rd

The Snow, Water, Ice and Permafrost in the Arctic (SWIPA) report, released in April 2012, is the latest assessment addressing Arctic change and its impacts. The focus is on the cryosphere. In this seminar, we will review the key findings of the SWIPA report. These findings begin with the contention that Arctic warmth over the past decades is unprecedented relative to several reconstructions. The findings then extend to the recent accelerated loss of sea ice and terrestrial snow cover, including feedbacks to the atmosphere. We will highlight the report's key findings about ongoing changes and future trajectories of permafrost, glaciers and ice caps, the Greenland ice sheet, and river and lake ice. We will then address the uncertainties in the report's estimates of (1) the timing of the projected disappearance of summer sea ice and (2) the projected contributions of Greenland and glacier ice loss to sea level rise. Finally, we will summarize the report's treatment of impacts on Arctic ecosystems and people.

May 17th

Increased attention is being paid to snow distributions, especially in high-latitude boreal systems. Managing agencies are interested in distributed snow measurements characterizing snow distribution patterns over vast areas, yet resources to conduct surveys are sparse. Regrettably, remote sensing approaches frequently fall short in boreal forest due to the canopy. Ground-based surveys can be time consuming where roads are scarce and people rely on snow machine trails and rivers. In March 2011, Cold Regions Research and Engineering Laboratory (CRREL), U.S. Fish and Wildlife Service (USFWS), and U.S. Geological Survey (USGS) scientists undertook a hybrid aerial- and ground-based snow survey to measure snow within Alaska's vast Yukon Flats National Wildlife Refuge. The overall goals of the snow survey were to 1) ascertain the feasibility of conducting aircraft-based surveys across the 36422 km2 Refuge, 2) determine if there were gradients in snow depth and snow water equivalent across the region, and 3) develop a monitoring system where future surveys can be done inexpensively. Over four days, measurements were made at 26 locations spanning an area that was 228 km west to east and 180 km south to north with varying canopy and terrain characteristics. The average depth for the entire Refuge was 59.7 cm (n=4994), which corresponds to 12.2 cm (n=180) SWE; the coincident Fort Yukon SNOTEL depth was 56 cm (the only domain first-order station location). SWE varied with elevation and region, yet considerable noise in SWE exists, indicating a strong local signal (e.g., vegetation and time since disturbance). The operational mode used in the project was safe, successful, cost-effective, and relatively efficient. It could be used in future years to collect data, a process that would illuminate snow trends that play a crucial role in boreal forest ecosystems.

May 31st

The Arctic Ocean is surrounded by permafrost, which is being degraded at an increasing rate under conditions of warming which are most pronounced in Siberia and Alaska. Sub-sea permafrost is much more vulnerable than its terrestrial counterpart, because it experienced a drastic change in its thermal regime due to inundation by the ocean and consequent warming by as much as 12-17˚C, prior to the current ongoing climate change. Thaw and release of organic carbon (OC) from Arctic permafrost is postulated to be one of the most powerful mechanisms causing a net redistribution of carbon from land and ocean to the atmosphere. This report summarizes current understanding of transport and fate of OC to and within the East Siberian Arctic Shelf (ESAS) and processes determining carbon dioxide (CO2) and methane (CH4) fluxes from the ESAS to the atmosphere achieved from analyzing the data sets obtained on 20 expeditions performed from 1999 to 2011. The shallow ESAS is a unique area of the World Ocean where ~80% of predicted sub-sea permafrost exists. This study of the ESAS was aimed at investigating how redistribution of old carbon from degrading terrestrial and sub-sea permafrost and from coastal erosion contributes to the carbon pool of the ESAS, and which factors control CH4 and CO2 emissions from the ESAS. This report describes selected results achieved by a developing international scientific partnership that has been crucial at every stage of the study and will be even more important in the future.