Carmack Eddy C.

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Eddy C.

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Now showing 1 - 9 of 9
  • Article
    Pacific Ocean inflow : influence on catastrophic reduction of sea ice cover in the Arctic Ocean
    (American Geophysical Union, 2006-04-21) Shimada, Koji ; Kamoshida, Takashi ; Itoh, Motoyo ; Nishino, Shigeto ; Carmack, Eddy C. ; McLaughlin, Fiona A. ; Zimmermann, Sarah ; Proshutinsky, Andrey
    The spatial pattern of recent ice reduction in the Arctic Ocean is similar to the distribution of warm Pacific Summer Water (PSW) that interflows the upper portion of halocline in the southern Canada Basin. Increases in PSW temperature in the basin are also well-correlated with the onset of sea-ice reduction that began in the late 1990s. However, increases in PSW temperature in the basin do not correlate with the temperature of upstream source water in the northeastern Bering Sea, suggesting that there is another mechanism which controls these concurrent changes in ice cover and upper ocean temperature. We propose a feedback mechanism whereby the delayed sea-ice formation in early winter, which began in 1997/1998, reduced internal ice stresses and thus allowed a more efficient coupling of anticyclonic wind forcing to the upper ocean. This, in turn, increased the flux of warm PSW into the basin and caused the catastrophic changes.
  • Article
    Penetration of the 1990s warm temperature anomaly of Atlantic Water in the Canada Basin
    (American Geophysical Union, 2004-10-16) Shimada, Koji ; McLaughlin, Fiona A. ; Carmack, Eddy C. ; Proshutinsky, Andrey ; Nishino, Shigeto ; Itoh, Motoyo
    Penetration of the 1990s warm temperature anomaly (WTA) of the Fram Strait branch of Atlantic Water (FSBW) in the Canada Basin is described using available temperature, salinity, and velocity data. The core temperatures of FSBW show distinct pathways. Over the Chukchi Borderland advective velocities of the FSBW are well-correlated with bottom topography. The resulting multifarious pathways over the Chukchi Borderland act to modulate and substantially increase the time scale of WTA spreading and advancement. Further downstream two WTA tongues are observed. One tongue followed the Beaufort Slope and, along this pathway, the core temperatures of FSBW decreased rapidly. The depth integrated value of heat content remained near constant however, suggesting enhanced vertical mixing. The second tongue debouched from the northern tip of the Northwind Ridge and spread eastward into the deep Canada Basin, suggesting a complex recirculation structure within the Beaufort Gyre.
  • Preprint
    Greater role for Atlantic inflows on sea-ice loss in the Eurasian Basin of the Arctic Ocean
    ( 2017-03) Polyakov, Igor V. ; Pnyushkov, Andrey ; Alkire, Matthew ; Ashik, Igor M. ; Baumann, Till M. ; Carmack, Eddy C. ; Goszczko, Ilona ; Guthrie, John D. ; Ivanov, Vladimir V. ; Kanzow, Torsten ; Krishfield, Richard A. ; Kwok, Ron ; Sundfjord, Arild ; Morison, James H. ; Rember, Robert ; Yulin, Alexander
    Arctic sea-ice loss is a leading indicator of climate change and can be attributed, in large part, to atmospheric forcing. Here we show that recent ice reductions, weakening of the halocline, and shoaling of intermediate-depth Atlantic Water layer in the eastern Eurasian Basin have increased winter ventilation in the ocean interior, making this region structurally similar to that of the western Eurasian Basin. The associated enhanced release of oceanic heat has reduced winter sea-ice formation at a rate now comparable to losses from atmospheric thermodynamic forcing, thus explaining the recent reduction in sea-ice cover in the eastern Eurasian Basin. This encroaching “atlantification” of the Eurasian Basin represents an essential step toward a new Arctic climate state, with a substantially greater role for Atlantic inflows.
  • Article
    Geochemistry of small Canadian Arctic rivers with diverse geological and hydrological settings
    (American Geophysical Union, 2020-01-03) Brown, Kristina A. ; Williams, William J. ; Carmack, Eddy C. ; Fiske, Gregory J. ; Francois, Roger ; McLennan, Donald ; Peucker-Ehrenbrink, Bernhard
    A survey of 25 coastal‐draining rivers across the Canadian Arctic Archipelago (CAA) shows that these systems are distinct from the largest Arctic rivers that drain watersheds extending far south of the Arctic circle. Observations collected from 2014 to 2016 illustrate the influences of seasonal hydrology, bedrock geology, and landscape physiography on each river's inorganic geochemical characteristics. Summertime data show the impact of coincident gradients in lake cover and surficial geology on river geochemical signatures. In the north and central CAA, drainage basins are generally smaller, underlain by sedimentary bedrock, and their hydrology is driven by seasonal precipitation pulses that undergo little modification before they enter the coastal ocean. In the southern CAA, a high density of lakes stores water longer within the terrestrial system, permitting more modification of water isotope and geochemical characteristics. Annual time‐series observations from two CAA rivers reveal that their concentration‐discharge relationships differ compared with those of the largest Arctic rivers, suggesting that future projections of dissolved ion fluxes from CAA rivers to the Arctic Ocean may not be reliably made based on compositions of the largest Arctic rivers alone, and that rivers draining the CAA region will likely follow different trajectories of change under a warming climate. Understanding how these small, coastal‐draining river systems will respond to climate change is essential to fully evaluate the impact of changing freshwater inputs to the Arctic marine system.
  • Article
    Deterioration of perennial sea ice in the Beaufort Gyre from 2003 to 2012 and its impact on the oceanic freshwater cycle
    (John Wiley & Sons, 2014-02-22) Krishfield, Richard A. ; Proshutinsky, Andrey ; Tateyama, Kazutaka ; Williams, William J. ; Carmack, Eddy C. ; McLaughlin, Fiona A. ; Timmermans, Mary-Louise
    Time series of ice draft from 2003 to 2012 from moored sonar data are used to investigate variability and describe the reduction of the perennial sea ice cover in the Beaufort Gyre (BG), culminating in the extreme minimum in 2012. Negative trends in median ice drafts and most ice fractions are observed, while open water and thinnest ice fractions (<0.3 m) have increased, attesting to the ablation or removal of the older sea ice from the BG over the 9 year period. Monthly anomalies indicate a shift occurred toward thinner ice after 2007, in which the thicker ice evident at the northern stations was reduced. Differences in the ice characteristics between all of the stations also diminished, so that the ice cover throughout the region became statistically homogenous. The moored data are used in a relationship with satellite radiometer data to estimate ice volume changes throughout the BG. Summer solid fresh water content decreased drastically in consecutive years from 730 km3 in 2006 to 570 km3 in 2007, and to 240 km3 in 2008. After a short rebound, solid fresh water fell below 220 km3 in 2012. Meanwhile, hydrographic data indicate that liquid fresh water in the BG in summer increased 5410 km3 from 2003 to 2010 and decreased at least 210 km3 by 2012. The reduction of both solid and liquid fresh water components indicates a net export of approximately 320 km3 of fresh water from the region occurred between 2010 and 2012, suggesting that the anticyclonic atmosphere-ocean circulation has weakened.
  • Article
    The rapid response of the Canada Basin to climate forcing : from bellwether to alarm bells
    (Oceanography Society, 2011-09) McLaughlin, Fiona A. ; Carmack, Eddy C. ; Proshutinsky, Andrey ; Krishfield, Richard A. ; Guay, Christopher K. ; Yamamoto-Kawai, Michiyo ; Jackson, Jennifer M. ; Williams, William J.
    Sea ice extent in the Arctic Ocean diminished significantly during the first decade of the 2000s, most particularly in the Canada Basin where the loss of both multiyear and first-year ice was greater than in the other three subbasins. Using data collected during basin-wide surveys conducted from 2003–2010 together with data collected during the 1990s and 2000s at one station in the southern Canada Basin, we investigate the response of the Canada Basin water column to this significant decrease in ice cover. Changes were evident from the surface down to the Atlantic layer: some changes were the result of Beaufort Gyre forcing on regional processes, others were the result of Arctic Ocean atmospheric forcing on a hemispheric scale and large-scale advection. These changes have troubling consequences for the ecosystem.
  • Article
    Toward quantifying the increasing role oceanic heat in sea ice loss in the new Arctic
    (American Meteorological Society, 2015-12) Carmack, Eddy C. ; Polyakov, Igor V. ; Padman, Laurie ; Fer, Ilker ; Hunke, Elizabeth C. ; Hutchings, Jennifer K. ; Jackson, Jennifer M. ; Kelley, Daniel E. ; Kwok, Ron ; Layton, Chantelle ; Melling, Humfrey ; Perovich, Donald K. ; Persson, Ola ; Ruddick, Barry R. ; Timmermans, Mary-Louise ; Toole, John M. ; Ross, Tetjana ; Vavrus, Steve ; Winsor, Peter
    The loss of Arctic sea ice has emerged as a leading signal of global warming. This, together with acknowledged impacts on other components of the Earth system, has led to the term “the new Arctic.” Global coupled climate models predict that ice loss will continue through the twenty-first century, with implications for governance, economics, security, and global weather. A wide range in model projections reflects the complex, highly coupled interactions between the polar atmosphere, ocean, and cryosphere, including teleconnections to lower latitudes. This paper summarizes our present understanding of how heat reaches the ice base from the original sources—inflows of Atlantic and Pacific Water, river discharge, and summer sensible heat and shortwave radiative fluxes at the ocean/ice surface—and speculates on how such processes may change in the new Arctic. The complexity of the coupled Arctic system, and the logistic and technological challenges of working in the Arctic Ocean, require a coordinated interdisciplinary and international program that will not only improve understanding of this critical component of global climate but will also provide opportunities to develop human resources with the skills required to tackle related problems in complex climate systems. We propose a research strategy with components that include 1) improved mapping of the upper- and middepth Arctic Ocean, 2) enhanced quantification of important process, 3) expanded long-term monitoring at key heat-flux locations, and 4) development of numerical capabilities that focus on parameterization of heat-flux mechanisms and their interactions.
  • Article
    Beaufort Gyre freshwater reservoir : state and variability from observations
    (American Geophysical Union, 2009-06-24) Proshutinsky, Andrey ; Krishfield, Richard A. ; Timmermans, Mary-Louise ; Toole, John M. ; Carmack, Eddy C. ; McLaughlin, Fiona A. ; Williams, William J. ; Zimmermann, Sarah ; Itoh, Motoyo ; Shimada, Koji
    We investigate basin-scale mechanisms regulating anomalies in freshwater content (FWC) in the Beaufort Gyre (BG) of the Arctic Ocean using historical observations and data collected in 2003–2007. Specifically, the mean annual cycle and interannual and decadal FWC variability are explored. The major cause of the large FWC in the BG is the process of Ekman pumping (EP) due to the Arctic High anticyclonic circulation centered in the BG. The mean seasonal cycle of liquid FWC is a result of interplay between the mechanical (EP) and thermal (ice transformations) factors and has two peaks. One peak occurs around June–July when the sea ice thickness reaches its minimum (maximum ice melt). The second maximum is observed in November–January when wind curl is strongest (maximum EP) and the salt input from the growing ice has not yet reached its maximum. Interannual changes in FWC during 2003–2007 are characterized by a strong positive trend in the region varying by location with a maximum of approximately 170 cm a−1 in the center of EP influenced region. Decadal FWC variability in the period 1950–2000 is dominated by a significant change in the 1990s forced by an atmospheric circulation regime change. The center of maximum FWC shifted to the southeast and appeared to contract in area relative to the pre-1990s climatology. In spite of the areal reduction, the spatially integrated FWC increased by over 1000 km3 relative to climatology.
  • Article
    Halocline structure in the Canada Basin of the Arctic Ocean
    (American Geophysical Union, 2005-02-05) Shimada, Koji ; Itoh, Motoyo ; Nishino, Shigeto ; McLaughlin, Fiona A. ; Carmack, Eddy C. ; Proshutinsky, Andrey
    We examine the varieties and spatial distributions of Pacific and Eastern Arctic origin halocline waters in the Canada Basin using 2002–2003 hydrographic data. The halocline structure in the Canada Basin is different from the Eastern Arctic halocline because it includes fresher Pacific Winter Waters that form a “cold halostad” which lies above the Eastern Arctic origin lower halocline waters. The structure of the halostad in the Canada Basin, however, is not spatially uniform, and depends on the pathway and history of the source water. Pacific Winter Water entering through the Bering Strait becomes salty due to sea ice formation and this, in turn, is dependent on the occurrence and distribution of polynyas. In particular, saline water from the eastern Chukchi Sea forms thick halostad and causes depression of the isohalines in the southern Canada Basin. This depression influences thermohaline structure of the oceanic Beaufort Gyre.