Arctic-COLORS (Coastal Land Ocean Interactions in the Arctic) - a NASA field campaign scoping study to examine land-ocean interactions in the Arctic

NASA Astrophysics Data System (ADS)

Hernes, P.; Tzortziou, M.; Salisbury, J.; Mannino, A.; Matrai, P.; Friedrichs, M. A.; Del Castillo, C. E.

2014-12-01

The Arctic region is warming faster than anywhere else on the planet, triggering rapid social and economic changes and impacting both terrestrial and marine ecosystems. Yet our understanding of critical processes and interactions along the Arctic land-ocean interface is limited. Arctic-COLORS is a Field Campaign Scoping Study funded by NASA's Ocean Biology and Biogeochemistry Program that aims to improve understanding and prediction of land-ocean interactions in a rapidly changing Arctic coastal zone, and assess vulnerability, response, feedbacks and resilience of coastal ecosystems, communities and natural resources to current and future pressures. Specific science objectives include: - Quantify lateral fluxes to the arctic inner shelf from (i) rivers and (ii) the outer shelf/basin that affect biology, biodiversity, biogeochemistry (i.e. organic matter, nutrients, suspended sediment), and the processing rates of these constituents in coastal waters. - Evaluate the impact of the thawing of Arctic permafrost within the river basins on coastal biology, biodiversity and biogeochemistry, including various rates of community production and the role these may play in the health of regional economies. - Assess the impact of changing Arctic landfast ice and coastal sea ice dynamics. - Establish a baseline for comparison to future change, and use state-of-the-art models to assess impacts of environmental change on coastal biology, biodiversity and biogeochemistry. A key component of Arctic-COLORS will be the integration of satellite and field observations with coupled physical-biogeochemical models for predicting impacts of future pressures on Arctic, coastal ocean, biological processes and biogeochemical cycles. Through interagency and international collaborations, and through the organization of dedicated workshops, town hall meetings and presentations at international conferences, the scoping study engages the broader scientific community and invites participation of

Diversity of planktonic microorganisms in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Pedrós-Alió, Carlos; Potvin, Marianne; Lovejoy, Connie

2015-12-01

The present paper begins by reviewing recent developments in our understanding of the diversity of planktonic microorganisms in the Arctic Ocean, taking into account recent data from high throughput sequencing techniques. This data has enabled deeper analysis of the many thousands of different microorganisms present in natural samples. The Arctic Ocean is similar to the other oceans in terms of the abundance and general composition of microbial communities. However, some traits are unique. For example, there are essentially no cyanobacteria in the Arctic and their ecological role seems to be taken up by picoeukaryotic algae. Recent comparisons of the bacterial communities from the two Polar oceans with those from temperate waters showed that Polar communities were closer to each other than to the lower latitude ones. However, they only shared about 15% of the taxa. Newer data considerably increases the coverage of Arctic sites sampled and indicates that bacterial communities in the Arctic vary significantly across regions and seasons. In particular several recent cruises have provided access to the Arctic Ocean during the winter, the least known season and we review two instances of active microbes during the winter. First a bloom of Thaumarchaeota that may have been based on the use of urea as a source of carbon and reducing power, and second the increase in picoeukaryotic algae as soon as light reaches the ocean in February. Both examples show that there is considerable microbial activity during the Polar winter.

Late Cretaceous seasonal ocean variability from the Arctic.

PubMed

Davies, Andrew; Kemp, Alan E S; Pike, Jennifer

2009-07-09

The modern Arctic Ocean is regarded as a barometer of global change and amplifier of global warming and therefore records of past Arctic change are critical for palaeoclimate reconstruction. Little is known of the state of the Arctic Ocean in the greenhouse period of the Late Cretaceous epoch (65-99 million years ago), yet records from such times may yield important clues to Arctic Ocean behaviour in near-future warmer climates. Here we present a seasonally resolved Cretaceous sedimentary record from the Alpha ridge of the Arctic Ocean. This palaeo-sediment trap provides new insight into the workings of the Cretaceous marine biological carbon pump. Seasonal primary production was dominated by diatom algae but was not related to upwelling as was previously hypothesized. Rather, production occurred within a stratified water column, involving specially adapted species in blooms resembling those of the modern North Pacific subtropical gyre, or those indicated for the Mediterranean sapropels. With increased CO(2) levels and warming currently driving increased stratification in the global ocean, this style of production that is adapted to stratification may become more widespread. Our evidence for seasonal diatom production and flux testify to an ice-free summer, but thin accumulations of terrigenous sediment within the diatom ooze are consistent with the presence of intermittent sea ice in the winter, supporting a wide body of evidence for low temperatures in the Late Cretaceous Arctic Ocean, rather than recent suggestions of a 15 degrees C mean annual temperature at this time.

Modes of Arctic Ocean Change from GRACE, ICESat and the PIOMAS and ECCO2 Models of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Peralta Ferriz, C.; Morison, J. H.; Bonin, J. A.; Chambers, D. P.; Kwok, R.; Zhang, J.

2012-12-01

EOF analysis of month-to-month variations in GRACE derived Arctic Ocean bottom pressure (OBP) with trend and seasonal variation removed yield three dominant modes. The first mode is a basin wide variation in mass associated with high atmospheric pressure (SLP) over Scandinavia mainly in winter. The second mode is a shift of mass from the central Arctic Ocean to the Siberian shelves due to low pressure over the basins, associated with the Arctic Oscillation. The third mode is a shift in mass between the Eastern and Western Siberian shelves, related to strength of the Beaufort High mainly in summer, and to eastward alongshore winds on the Barents Sea in winter. The PIOMAS and ECCO2 modeled OBP show fair agreement with the form of these modes and provide context in terms of variations in sea surface height SSH. Comparing GRACE OBP from 2007 to 2011 with GRACE OBP from 2002 to 2006 reveals a rising trend over most of the Arctic Ocean but declines in the Kara Sea region and summer East Siberian Sea. ECCO2 bears a faint resemblance to the observed OBP change but appears to be biased negatively. In contrast, PIOMAS SSH and ECCO2 especially, show changes between the two periods that are muted but similar to ICESat dynamic ocean topography and GRACE-ICESat freshwater trends from 2005 through 2008 [Morison et al., 2012] with a rising DOT and freshening in the Beaufort Sea and a trough with decreased freshwater on the Russian side of the Arctic Ocean. Morison, J., R. Kwok, C. Peralta-Ferriz, M. Alkire, I. Rigor, R. Andersen, and M. Steele (2012), Changing Arctic Ocean freshwater pathways, Nature, 481(7379), 66-70.

Drivers of Arctic Ocean warming in CMIP5 models

NASA Astrophysics Data System (ADS)

Burgard, Clara; Notz, Dirk

2017-05-01

We investigate changes in the Arctic Ocean energy budget simulated by 26 general circulation models from the Coupled Model Intercomparison Project Phase 5 framework. Our goal is to understand whether the Arctic Ocean warming between 1961 and 2099 is primarily driven by changes in the net atmospheric surface flux or by changes in the meridional oceanic heat flux. We find that the simulated Arctic Ocean warming is driven by positive anomalies in the net atmospheric surface flux in 11 models, by positive anomalies in the meridional oceanic heat flux in 11 models, and by positive anomalies in both energy fluxes in four models. The different behaviors are mainly characterized by the different changes in meridional oceanic heat flux that lead to different changes in the turbulent heat loss to the atmosphere. The multimodel ensemble mean is hence not representative of a consensus across the models in Arctic climate projections.

Arctic pathways of Pacific Water: Arctic Ocean Model Intercomparison experiments

PubMed Central

Karcher, Michael; Proshutinsky, Andrey; Gerdes, Rüdiger; de Cuevas, Beverly; Golubeva, Elena; Kauker, Frank; Nguyen, An T.; Platov, Gennady A.; Wadley, Martin; Watanabe, Eiji; Coward, Andrew C.; Nurser, A. J. George

2016-01-01

Abstract Pacific Water (PW) enters the Arctic Ocean through Bering Strait and brings in heat, fresh water, and nutrients from the northern Bering Sea. The circulation of PW in the central Arctic Ocean is only partially understood due to the lack of observations. In this paper, pathways of PW are investigated using simulations with six state‐of‐the art regional and global Ocean General Circulation Models (OGCMs). In the simulations, PW is tracked by a passive tracer, released in Bering Strait. Simulated PW spreads from the Bering Strait region in three major branches. One of them starts in the Barrow Canyon, bringing PW along the continental slope of Alaska into the Canadian Straits and then into Baffin Bay. The second begins in the vicinity of the Herald Canyon and transports PW along the continental slope of the East Siberian Sea into the Transpolar Drift, and then through Fram Strait and the Greenland Sea. The third branch begins near the Herald Shoal and the central Chukchi shelf and brings PW into the Beaufort Gyre. In the models, the wind, acting via Ekman pumping, drives the seasonal and interannual variability of PW in the Canadian Basin of the Arctic Ocean. The wind affects the simulated PW pathways by changing the vertical shear of the relative vorticity of the ocean flow in the Canada Basin. PMID:27818853

Arctic pathways of Pacific Water: Arctic Ocean Model Intercomparison experiments.

PubMed

Aksenov, Yevgeny; Karcher, Michael; Proshutinsky, Andrey; Gerdes, Rüdiger; de Cuevas, Beverly; Golubeva, Elena; Kauker, Frank; Nguyen, An T; Platov, Gennady A; Wadley, Martin; Watanabe, Eiji; Coward, Andrew C; Nurser, A J George

2016-01-01

Pacific Water (PW) enters the Arctic Ocean through Bering Strait and brings in heat, fresh water, and nutrients from the northern Bering Sea. The circulation of PW in the central Arctic Ocean is only partially understood due to the lack of observations. In this paper, pathways of PW are investigated using simulations with six state-of-the art regional and global Ocean General Circulation Models (OGCMs). In the simulations, PW is tracked by a passive tracer, released in Bering Strait. Simulated PW spreads from the Bering Strait region in three major branches. One of them starts in the Barrow Canyon, bringing PW along the continental slope of Alaska into the Canadian Straits and then into Baffin Bay. The second begins in the vicinity of the Herald Canyon and transports PW along the continental slope of the East Siberian Sea into the Transpolar Drift, and then through Fram Strait and the Greenland Sea. The third branch begins near the Herald Shoal and the central Chukchi shelf and brings PW into the Beaufort Gyre. In the models, the wind, acting via Ekman pumping, drives the seasonal and interannual variability of PW in the Canadian Basin of the Arctic Ocean. The wind affects the simulated PW pathways by changing the vertical shear of the relative vorticity of the ocean flow in the Canada Basin.

Quaternary dinoflagellate cysts in the Arctic Ocean: Potential and limitations for stratigraphy and paleoenvironmental reconstructions

NASA Astrophysics Data System (ADS)

Matthiessen, Jens; Schreck, Michael; De Schepper, Stijn; Zorzi, Coralie; de Vernal, Anne

2018-07-01

The Arctic Ocean is a siliciclastic depositional environment which lacks any rock-forming biogenic calcareous and siliceous components during large parts of its Quaternary history. These hemipelagic sediments are nevertheless suitable for the study of organic-walled microfossils of which the fossil remains of dinoflagellates - dinoflagellate cysts - are the most important group. Dinoflagellate cysts have become an important tool in paleoceanography of the high northern latitudes, but their potential for Quaternary biostratigraphy has remained largely unexplored. Dinoflagellate cysts are the dominant marine palynomorph group which is more continuously present in the marginal seas (e.g. Barents Sea, Bering Sea) than in the Arctic Ocean itself throughout the Quaternary. Most species have long stratigraphic ranges, are temporary absent and show abundance variations on glacial-interglacial timescales. Of the more than 30 taxa recorded, only Habibacysta tectata and Filisphaera filifera became extinct in the Pleistocene. The highest persistent occurrence of H. tectata at ca. 2.0 Ma and the top of F. filifera acme at ca. 1.8 Ma can be used for supra-regional stratigraphic correlation between the Arctic Ocean and adjacent basins. These events corroborate a slow sedimentation rate model for the Quaternary section on the central Lomonosov Ridge, but a combination of different methods will have to be applied to provide a detailed chronostratigraphy. The occurrence of cysts of phototrophic dinoflagellates in certain stratigraphic intervals on Lomonosov Ridge supports published evidence of episodic opening of the multiyear Arctic sea ice cover during the Quaternary probably related to a stronger inflow of Atlantic water. This contradicts the hypothesis of a permanently ice covered central Arctic Ocean in the Quaternary.

The Role and Variability of Ocean Heat Content in the Arctic Ocean: 1948-2009

DTIC Science & Technology

2014-06-01

moved from the Bering Sea past the Bering Strait into the Beaufort Sea (Logerwell 2008). However, besides the risks of ocean acidification and...VARIABILITY OF OCEAN HEAT CONTENT IN THE ARCTIC OCEAN : 1948–2009 by Dominic F. DiMaggio June 2014 Thesis Co-Advisors: Wieslaw Maslowski...COVERED Master’s Thesis 4. TITLE AND SUBTITLE THE ROLE AND VARIABILITY OF OCEAN HEAT CONTENT IN THE ARCTIC OCEAN : 1948–2009 5. FUNDING NUMBERS 6

Subsurface phytoplankton layers in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Tremblay, J. E.

2016-02-01

Recent observations underscored the near-ubiquitous presence of subsurface chlorophyll maxima (SCM) and their potential importance for total primary production (PP) and pelagic food webs in perennially stratified waters of the Arctic Ocean. The contribution of SCM layers to annual PP is particularly important in oligotrophic areas, where modest nutrient supply to the upper euphotic zone results in weak or short-lived phytoplankton blooms near the surface. The large amount of nutrients present in the Pacific halocline relative to comparable depths in the Atlantic sector of the Arctic may also foster particularly productive SCM along the path of Pacific water. The association between strongly stratified conditions and the SCM in today's Arctic Ocean has broad relevance in providing a glimpse into the future of other oceans whose vertical stratification progressively rises with water temperature and freshwater content. In this regard, there is much to learn on the photosynthetic and nutritive ecology of SCM layers, whose biogeochemical significance depends on the extent to which they rely on allochthonous nitrogen (new production), their contribution to carbon biomass and their ability to influence air-sea CO2 exchange. Here we report on several years of eco-physiological investigations of SCM across the Arctic Ocean, with an aim to provide a basis of comparison with the ecology of SCM in other ocean areas.

Future scientific drilling in the Arctic Ocean: Key objectives, areas, and strategies

NASA Astrophysics Data System (ADS)

Stein, R.; Coakley, B.; Mikkelsen, N.; O'Regan, M.; Ruppel, C.

2012-04-01

In spite of the critical role of the Arctic Ocean in climate evolution, our understanding of the short- and long-term paleoceanographic and paleoclimatic history through late Mesozoic-Cenozoic times, as well as its plate-tectonic evolution, remains behind that from the other world's oceans. This lack of knowledge is mainly caused by the major technological/logistic problems in reaching this permanently ice-covered region with normal research vessels and in retrieving long and undisturbed sediment cores. With the Arctic Coring Expedition - ACEX (or IODP Expedition 302), the first Mission Specific Platform (MSP) expedition within IODP, a new era in Arctic research began (Backman, Moran, Mayer, McInroy et al., 2006). ACEX proved that, with an intensive ice-management strategy, successful scientific drilling in the permanently ice-covered central Arctic Ocean is possible. ACEX is certainly a milestone in Arctic Ocean research, but - of course - further drilling activities are needed in this poorly studied ocean. Furthermore, despite the success of ACEX fundamental questions related to the long- and short-term climate history of the Arctic Ocean during Mesozoic-Cenozoic times remain unanswered. This is partly due to poor core recovery during ACEX and, especially, because of a major mid-Cenozoic hiatus in this single record. Since ACEX, a series of workshops were held to develop a scientific drilling strategy for investigating the tectonic and paleoceanographic history of the Arctic Ocean and its role in influencing the global climate system: - "Arctic Ocean History: From Speculation to Reality" (Bremerhaven/Germany, November 2008); - "Overcoming barriers to Arctic Ocean scientific drilling: the site survey challenge" (Copenhagen/Denmark, November 2011); - Circum-Arctic shelf/upper continental slope scientific drilling workshop on "Catching Climate Change in Progress" (San Francisco/USA, December 2011); - "Coordinated Scientific Drilling in the Beaufort Sea: Addressing

Continental Margins of the Arctic Ocean: Implications for Law of the Sea

NASA Astrophysics Data System (ADS)

Mosher, David

2016-04-01

A coastal State must define the outer edge of its continental margin in order to be entitled to extend the outer limits of its continental shelf beyond 200 M, according to article 76 of the UN Convention on the Law of the Sea. The article prescribes the methods with which to make this definition and includes such metrics as water depth, seafloor gradient and thickness of sediment. Note the distinction between the "outer edge of the continental margin", which is the extent of the margin after application of the formula of article 76, and the "outer limit of the continental shelf", which is the limit after constraint criteria of article 76 are applied. For a relatively small ocean basin, the Arctic Ocean reveals a plethora of continental margin types reflecting both its complex tectonic origins and its diverse sedimentation history. These factors play important roles in determining the extended continental shelves of Arctic coastal States. This study highlights the critical factors that might determine the outer edge of continental margins in the Arctic Ocean as prescribed by article 76. Norway is the only Arctic coastal State that has had recommendations rendered by the Commission on the Limits of the Continental Shelf (CLCS). Russia and Denmark (Greenland) have made submissions to the CLCS to support their extended continental shelves in the Arctic and are awaiting recommendations. Canada has yet to make its submission and the US has not yet ratified the Convention. The various criteria that each coastal State has utilized or potentially can utilize to determine the outer edge of the continental margin are considered. Important criteria in the Arctic include, 1) morphological continuity of undersea features, such as the various ridges and spurs, with the landmass, 2) the tectonic origins and geologic affinities with the adjacent land masses of the margins and various ridges, 3) sedimentary processes, particularly along continental slopes, and 4) thickness and

Research Spotlight: No tipping point for Arctic Ocean ice

NASA Astrophysics Data System (ADS)

Schultz, Colin

2011-03-01

Declines in the summer sea ice extent have led to concerns within the scientific community that the Arctic Ocean may be nearing a tipping point, beyond which the sea ice cap could not recover. In such a scenario, greenhouse gases in the atmosphere trap outgoing radiation, and as the Sun beats down 24 hours a day during the Arctic summer, temperatures rise and melt what remains of the polar sea ice cap. The Arctic Ocean, now less reflective, would absorb more of the Sun’s warmth, a feedback loop that would keep the ocean ice free. However, new research by Tietsche et al. suggests that even if the Arctic Ocean sees an ice-free summer, it would not lead to catastrophic runaway ice melt. The researchers, using a general circulation model of the global ocean and the atmosphere, found that Arctic sea ice recovers within 2 years of an imposed ice-free summer to the conditions dictated by general climate conditions during that time. Furthermore, they found that this quick recovery occurs whether the ice-free summer is triggered in 2000 or in 2060, when global temperatures are predicted to be 2°C warmer. (Geophysical Research Letters, doi:10.1029/2010GL045698, 2011)

Arctic Ocean Circulation Patterns Revealed by GRACE

NASA Astrophysics Data System (ADS)

Peralta-Ferriz, Cecilia; Morison, James H.; Wallace, John M.; Bonin, Jennifer A.; Zhang, Jinlun

2013-04-01

EOF analysis of non-seasonal, month-to-month variations in GRACE derived Arctic Ocean bottom pressure (OBP) yield three dominant modes. The first mode is a wintertime basin wide variation in mass associated with high atmospheric pressure (SLP) over Scandinavia. The second mode is a shift of mass from the central Arctic Ocean to the Siberian shelves due to low pressure over the basins, associated with the strength of the Arctic Oscillation. The third mode is a shift in mass between the Eastern and Western Siberian shelves, related to strength of the Beaufort High mainly in summer, and to eastward alongshore winds on the Barents Sea in winter. The PIOMAS and ECCO2 modeled OBP are consistent with the form of these modes and provide context in terms of variations in sea surface height. The models are used to investigate the ocean dynamics associated with each mode of OBP variability.

Pan-Arctic distributions of continental runoff in the Arctic Ocean

PubMed Central

Fichot, Cédric G.; Kaiser, Karl; Hooker, Stanford B.; Amon, Rainer M. W.; Babin, Marcel; Bélanger, Simon; Walker, Sally A.; Benner, Ronald

2013-01-01

Continental runoff is a major source of freshwater, nutrients and terrigenous material to the Arctic Ocean. As such, it influences water column stratification, light attenuation, surface heating, gas exchange, biological productivity and carbon sequestration. Increasing river discharge and thawing permafrost suggest that the impacts of continental runoff on these processes are changing. Here, a new optical proxy was developed and implemented with remote sensing to determine the first pan-Arctic distribution of terrigenous dissolved organic matter (tDOM) and continental runoff in the surface Arctic Ocean. Retrospective analyses revealed connections between the routing of North American runoff and the recent freshening of the Canada Basin, and indicated a correspondence between climate-driven changes in river discharge and tDOM inventories in the Kara Sea. By facilitating the real-time, synoptic monitoring of tDOM and freshwater runoff in surface polar waters, this novel approach will help understand the manifestations of climate change in this remote region. PMID:23316278

Pan-Arctic distributions of continental runoff in the Arctic Ocean.

PubMed

Fichot, Cédric G; Kaiser, Karl; Hooker, Stanford B; Amon, Rainer M W; Babin, Marcel; Bélanger, Simon; Walker, Sally A; Benner, Ronald

2013-01-01

Continental runoff is a major source of freshwater, nutrients and terrigenous material to the Arctic Ocean. As such, it influences water column stratification, light attenuation, surface heating, gas exchange, biological productivity and carbon sequestration. Increasing river discharge and thawing permafrost suggest that the impacts of continental runoff on these processes are changing. Here, a new optical proxy was developed and implemented with remote sensing to determine the first pan-Arctic distribution of terrigenous dissolved organic matter (tDOM) and continental runoff in the surface Arctic Ocean. Retrospective analyses revealed connections between the routing of North American runoff and the recent freshening of the Canada Basin, and indicated a correspondence between climate-driven changes in river discharge and tDOM inventories in the Kara Sea. By facilitating the real-time, synoptic monitoring of tDOM and freshwater runoff in surface polar waters, this novel approach will help understand the manifestations of climate change in this remote region.

Hypsometry, volume and physiography of the Arctic Ocean and their paleoceanographic implications

NASA Astrophysics Data System (ADS)

Jakobsson, M.; Macnab, R.; Grantz, A.; Kristoffersen, Y.

2003-04-01

Recent analyses of the International Bathymetric Chart of the Arctic Ocean (IBCAO) grid model include: Hypsometry (the distribution of surface area at various depths); ocean volume distribution; and physiographic provinces [Jakobsson 2002; Jakobsson et al., in press]. The present paper summarizes the main results from these recent studies and expands on the paleoceanographic implications for the Arctic Ocean, which in this work is defined as the broad continental shelves of the Barents, Kara, Laptev, East Siberian and Chukchi Seas, the White Sea and the narrow continental shelves of the Beaufort Sea, the Arctic continental margins off the Canadian Arctic Archipelago and northern Greenland. This, the World's smallest ocean, is a virtually land-locked ocean that makes up merely 2.6 % of the area, and 1.0 % of the volume, of the entire World Ocean. The continental shelf area, from the coastline out to the shelf break, comprises as much as 52.9 % of the total area in the Arctic Ocean, which is significantly larger in comparison to the rest of the world oceans where the proportion of shelves, from the coastline out to the foot of the continental slope, only ranges between about 9.1 % and 17.7 %. In Jakobsson [2002], the seafloor area and water volume were calculated for different depths starting from the present sea level and progressing in increments of 10 m to a depth of 500 m, and in increments of 50 m from 550 m down to the deepest depth within each of the analyzed Arctic Ocean seas. Hypsometric curves expressed as simple histograms of the frequencies in different depth bins were presented, along with depth plotted against cumulative area for each of the analyzed seas. The derived hypsometric curves show that most of the Arctic Ocean shelf seas besides the Barents Sea, Beaufort Sea and the shelf off northern Greenland have a similar shape with the largest seafloor area between 0 and 50 m. The East Siberian and Laptev seas, in particular, show area distributions

JAMSTEC Compact Arctic Drifter (J-CAD): A new Generation drifting buoy to observe the Arctic Ocean

NASA Astrophysics Data System (ADS)

Hatakeyama, Kiyoshi; Hosono, Masuo; Shimada, Koji; Kikuchi, Takashi; Nishino, Shigeto

The Arctic Ocean is one of the most sensitive regions to the earth environment changes. Japan Marine Science and Technology Center developed a new drift buoy to observe the Arctic Ocean. The name of the buoy is J-CAD (JAMSTEC Compact Arctic Drifter). From 1991 to 1993, JAMSTEC developed Ice-Ocean Environmental Buoy (IOEB) as a buoy to observe the Arctic Ocean in cooperation with Woods Hole Oceanographic Institution. The J-CAD is the buoy, which adopted the latest technology based on the knowledge and experience of IOEB development. The J-CAD was designed and developed by JAMSTEC and made by a Canadian Company MetOcean. JAMSTEC did design and development, and a Canadian company Met-Ocean made the J-CAD. It acquires meteorological and oceanographic data of the Arctic Ocean, and transmits the data that it measured via satellite. It dose also store the data inside its memory. An Inductive Modem system, which was developed by Sea-Bird Electronics, Inc. in the United States, was adopted in the underwater transmission system that data on each ocean sensor were collected. An ORBCOMM communication system was adopted for the satellite data transmission. J-CAD-1 was installed at 89°41'N 130°20'W on April 24, 2000, and the observation was started. August 1st was the day when 100 days have passed since the J-CAD-1 was installed on the North Pole. And now, the distance J-CAD-1 has covered exceeds 400 km, and it has transmitted data more than 500 k byte. A part of the data is introduced to the public in the homepage (http://w3.jamstec.go.jp: 8338) of the Arctic research group of JAMSTEC.

Mean Dynamic Topography of the Arctic Ocean

NASA Technical Reports Server (NTRS)

Farrell, Sinead Louise; Mcadoo, David C.; Laxon, Seymour W.; Zwally, H. Jay; Yi, Donghui; Ridout, Andy; Giles, Katherine

2012-01-01

ICESat and Envisat altimetry data provide measurements of the instantaneous sea surface height (SSH) across the Arctic Ocean, using lead and open water elevation within the sea ice pack. First, these data were used to derive two independent mean sea surface (MSS) models by stacking and averaging along-track SSH profiles gathered between 2003 and 2009. The ICESat and Envisat MSS data were combined to construct the high-resolution ICEn MSS. Second, we estimate the 5.5-year mean dynamic topography (MDT) of the Arctic Ocean by differencing the ICEn MSS with the new GOCO02S geoid model, derived from GRACE and GOCE gravity. Using these satellite-only data we map the major features of Arctic Ocean dynamical height that are consistent with in situ observations, including the topographical highs and lows of the Beaufort and Greenland Gyres, respectively. Smaller-scale MDT structures remain largely unresolved due to uncertainties in the geoid at short wavelengths.

The emergence of modern sea ice cover in the Arctic Ocean.

PubMed

Knies, Jochen; Cabedo-Sanz, Patricia; Belt, Simon T; Baranwal, Soma; Fietz, Susanne; Rosell-Melé, Antoni

2014-11-28

Arctic sea ice coverage is shrinking in response to global climate change and summer ice-free conditions in the Arctic Ocean are predicted by the end of the century. The validity of this prediction could potentially be tested through the reconstruction of the climate of the Pliocene epoch (5.33-2.58 million years ago), an analogue of a future warmer Earth. Here we show that, in the Eurasian sector of the Arctic Ocean, ice-free conditions prevailed in the early Pliocene until sea ice expanded from the central Arctic Ocean for the first time ca. 4 million years ago. Amplified by a rise in topography in several regions of the Arctic and enhanced freshening of the Arctic Ocean, sea ice expanded progressively in response to positive ice-albedo feedback mechanisms. Sea ice reached its modern winter maximum extension for the first time during the culmination of the Northern Hemisphere glaciation, ca. 2.6 million years ago.

Deep Arctic Ocean warming during the last glacial cycle

USGS Publications Warehouse

Cronin, T. M.; Dwyer, G.S.; Farmer, J.; Bauch, H.A.; Spielhagen, R.F.; Jakobsson, M.; Nilsson, J.; Briggs, W.M.; Stepanova, A.

2012-01-01

In the Arctic Ocean, the cold and relatively fresh water beneath the sea ice is separated from the underlying warmer and saltier Atlantic Layer by a halocline. Ongoing sea ice loss and warming in the Arctic Ocean have demonstrated the instability of the halocline, with implications for further sea ice loss. The stability of the halocline through past climate variations is unclear. Here we estimate intermediate water temperatures over the past 50,000 years from the Mg/Ca and Sr/Ca values of ostracods from 31 Arctic sediment cores. From about 50 to 11 kyr ago, the central Arctic Basin from 1,000 to 2,500 m was occupied by a water mass we call Glacial Arctic Intermediate Water. This water mass was 1–2 °C warmer than modern Arctic Intermediate Water, with temperatures peaking during or just before millennial-scale Heinrich cold events and the Younger Dryas cold interval. We use numerical modelling to show that the intermediate depth warming could result from the expected decrease in the flux of fresh water to the Arctic Ocean during glacial conditions, which would cause the halocline to deepen and push the warm Atlantic Layer into intermediate depths. Although not modelled, the reduced formation of cold, deep waters due to the exposure of the Arctic continental shelf could also contribute to the intermediate depth warming.

Arctic Ocean Gravity Field Derived From ERS-1 Satellite Altimetry.

PubMed

Laxon, S; McAdoo, D

1994-07-29

The derivation of a marine gravity field from satellite altimetry over permanently ice-covered regions of the Arctic Ocean provides much new geophysical information about the structure and development of the Arctic sea floor. The Arctic Ocean, because of its remote location and perpetual ice cover, remains from a tectonic point of view the most poorly understood ocean basin on Earth. A gravity field has been derived with data from the ERS-1 radar altimeter, including permanently ice-covered regions. The gravity field described here clearly delineates sections of the Arctic Basin margin along with the tips of the Lomonosov and Arctic mid-ocean ridges. Several important tectonic features of the Amerasia Basin are clearly expressed in this gravity field. These include the Mendeleev Ridge; the Northwind Ridge; details of the Chukchi Borderland; and a north-south trending, linear feature in the middle of the Canada Basin that apparently represents an extinct spreading center that "died" in the Mesozoic. Some tectonic models of the Canada Basin have proposed such a failed spreading center, but its actual existence and location were heretofore unknown.

Mercury genomics in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Bowman, K.; Lamborg, C. H.; Collins, E.; Hammerschmidt, C. R.; Agather, A. M.

2017-12-01

Methyl-mercury production in the ocean is likely dependent on microbial activity, however, methylation pathways remain elusive. In the Arctic, high concentrations of methyl-mercury are found in top predator marine mammals and seabirds. As a result of seafood consumption, pregnant women and women of child-bearing age in the Arctic often have blood Hg concentrations that exceed U.S. and Canadian safety guidelines. To understand the chemical cycling of mercury in the Arctic Ocean we participated in the 2015 U.S. GEOTRACES Arctic expedition (GN01) to measure Hg speciation in the water column of the Bering Sea, Makarov basin, and Canada basin between Dutch Harbor, Alaska and the North Pole. At select stations, seawater was filtered through 0.22 µm Sterivex filters and genomic DNA was collected using a phenol-chloroform extraction. Broad-range degenerate PCR primers were used to detect the presence of hgcAB, and clade-specific degenerate quantitative PCR primers were used to determine the abundance of hgcA. Metagenomic sequencing was done at three stations to identify taxonomic and functional groups, and to search for hgcA-like genes that the PCR primers may have missed.

A Meteoric Water Budget for the Arctic Ocean

NASA Astrophysics Data System (ADS)

Alkire, Matthew B.; Morison, James; Schweiger, Axel; Zhang, Jinlun; Steele, Michael; Peralta-Ferriz, Cecilia; Dickinson, Suzanne

2017-12-01

A budget of meteoric water (MW = river runoff, net precipitation minus evaporation, and glacial meltwater) over four regions of the Arctic Ocean is constructed using a simple box model, regional precipitation-evaporation estimates from reanalysis data sets, and estimates of import and export fluxes derived from the literature with a focus on the 2003-2008 period. The budget indicates an approximate/slightly positive balance between MW imports and exports (i.e., no change in storage); thus, the observed total freshwater increase observed during this time period likely resulted primarily from changes in non-MW freshwater components (i.e., increases in sea ice melt or Pacific water and/or a decrease in ice export). Further, our analysis indicates that the MW increase observed in the Canada Basin resulted from a spatial redistribution of MW over the Arctic Ocean. Mean residence times for MW were estimated for the Western Arctic (5-7 years), Eastern Arctic (3-4 years), and Lincoln Sea (1-2 years). The MW content over the Siberian shelves was estimated (˜14,000 km3) based on a residence time of 3.5 years. The MW content over the entire Arctic Ocean was estimated to be ≥44,000 km3. The MW export through Fram Strait consisted mostly of water from the Eastern Arctic (3,237 ± 1,370 km3 yr-1) whereas the export through the Canadian Archipelago was nearly equally derived from both the Western Arctic (1,182 ± 534 km3 yr-1) and Lincoln Sea (972 ± 391 km3 yr-1).

Scientific Drilling in the Arctic Ocean: A challenge for the next decades

NASA Astrophysics Data System (ADS)

Stein, R.; Coakley, B.

2009-04-01

Although major progress in Arctic Ocean research has been made during the last decades, the knowledge of its short- and long-term paleoceanographic and paleoclimatic history as well as its plate-tectonic evolution is much behind that from the other world's oceans. That means - despite the importance of the Arctic in the climate system - the data base we have from this area is still very weak, and large parts of the climate history have not been recovered at all in sedimentary sections. This lack of knowledge is mainly caused by the major technological/ logistic problems in reaching this permanently ice-covered region with normal research vessels and in retrieving long and undisturbed sediment cores. With the successful completion of IODP Expedition 302 ("Arctic Coring Expedition" - ACEX), the first Mission Specific Platform (MSP) expedition within the Integrated Ocean Drilling Program - IODP, a new era in Arctic research has begun. For the first time, a scientific drilling in the permanently ice-covered Arctic Ocean was carried out, penetrating about 430 meters of Quaternary, Neogene, Paleogene and Campanian sediment on the crest of Lomonosov Ridge close to the North Pole. The success of ACEX has certainly opened the door for further scientific drilling in the Arctic Ocean, and will frame the next round of questions to be answered from new drill holes to be taken during the next decades. In order to discuss and plan the future of scientific drilling in the Arctic Ocean, an international workshop was held at the Alfred Wegener Institute (AWI) in Bremerhaven/Germany, (Nov 03-05, 2008; convenors: Bernard Coakley/University of Alaska Fairbanks and Ruediger Stein/AWI Bremerhaven). About 95 scientists from Europe, US, Canada, Russia, Japan, and Korea, and observers from oil companies participated in the workshop. Funding of the workshop was provided by the Consortium for Ocean Leadership (US), the European Science Foundation, the Arctic Ocean Sciences Board, and the

Status and trends in Arctic biodiversity - Synthesis: implications for conservation

USDA-ARS?s Scientific Manuscript database

Arctic biodiversity – the multitude of species and ecosystems in the land north of the tree line together with the Arctic Ocean and adjacent seas – is an irreplaceable cultural, aesthetic, scientific, ecological, economic and spiritual asset. For Arctic peoples, biodiversity has been the very basis ...

Arctic Ocean circulation during the anoxic Eocene Azolla event

NASA Astrophysics Data System (ADS)

Speelman, Eveline; Sinninghe Damsté, Jaap; März, Christian; Brumsack, Hans; Reichart, Gert-Jan

2010-05-01

The Azolla interval, as encountered in Eocene sediments from the Arctic Ocean, is characterized by organic rich sediments ( 4wt% Corg). In general, high levels of organic matter may be caused by increased productivity, i.e. extensive growth of Azolla, and/or enhanced preservation of organic matter, or a combination of both. Anoxic (bottom) water conditions, expanded oxygen minimum zones, or increased sedimentation rates all potentially increase organic matter preservation. According to plate tectonic, bathymetric, and paleogeographic reconstructions, the Arctic Ocean was a virtually isolated shallow basin, with one possible deeper connection to the Nordic Seas represented by a still shallow Fram Strait (Jakobsson et al., 2007), hampering ventilation of the Arctic Basin. During the Azolla interval surface waters freshened, while at the same time bottom waters appear to have remained saline, indicating that the Arctic was highly stratified. The restricted ventilation and stratification in concert with ongoing export of organic matter most likely resulted in the development of anoxic conditions in the lower part of the water column. Whereas the excess precipitation over evaporation maintained the freshwater lid, sustained input of Nordic Sea water is needed to keep the deeper waters saline. To which degree the Arctic Ocean exchanged with the Nordic Seas is, however, still largely unknown. Here we present a high-resolution trace metal record (ICP-MS and ICP-OES) for the expanded Early/Middle Eocene section capturing the Azolla interval from Integrated Ocean Drilling Program (IODP) Expedition 302 (ACEX) drilled on the Lomonosov Ridge, central Arctic Ocean. Euxinic conditions throughout the interval resulted in the efficient removal of redox sensitive trace metals from the water column. Using the sedimentary trace metal record we also constrained circulation in the Arctic Ocean by assessing the relative importance of trace metal input sources (i.e. fluvial, eolian, and

Modern benthic foraminifer distribution in the Amerasian Basin, Arctic Ocean

USGS Publications Warehouse

Ishman, S.E.; Foley, K.M.

1996-01-01

A total of 38 box cores were collected from the Amerasian Basin, Arctic Ocean during the U.S. Geological Survey 1992 (PI92-AR) and 1993 (PI93-AR) Arctic Cruises aboard the U.S. Coast Guard Icebreaker Polar Star. In addition, the cruises collected geophysical data, piston cores and hydrographic data to address the geologic and oceanographic history of the western Arctic Ocean. This paper reports the results of the quantitative analyses of benthic foraminifer distribution data of the total (live + dead) assemblages derived from 22 box core-top samples. The results show that a distinct depth distribution of three dominant benthic foraminifer assemblages, the Textularia spp. - Spiroplectammina biformis, Cassidulina teretis and Oridorsalis tener - Eponides tumidulus Biofacies are strongly controlled by the dominant water masses within the Canada Basin: the Arctic Surface Water, Arctic Intermediate Water and Canada Basin Deep Water. The faunal distributions and their oceanographic associations in the Canada Basin are consistent with observations of benthic foraminifer distributions from other regions within the Arctic Ocean.

Pan-Arctic Distributions of Continental Runoff in the Arctic Ocean

DTIC Science & Technology

2013-01-11

lignin is well established as a biomarker of tDOM in oceanic waters10,11 and has been successfully applied as a tracer of riverine inputs in the... Lignin is also an important chro- mophore in tDOM, a property that facilitates detection using optical properties. Here, we demonstrate that the spectral...solved lignin and tDOM across various river-influenced ocean mar- gins of the Arctic Ocean12,13 (Fig. 1a). An increase in S2752295 is indicative of a

Retention of ice-associated amphipods: possible consequences for an ice-free Arctic Ocean.

PubMed

Berge, J; Varpe, O; Moline, M A; Wold, A; Renaud, P E; Daase, M; Falk-Petersen, S

2012-12-23

Recent studies predict that the Arctic Ocean will have ice-free summers within the next 30 years. This poses a significant challenge for the marine organisms associated with the Arctic sea ice, such as marine mammals and, not least, the ice-associated crustaceans generally considered to spend their entire life on the underside of the Arctic sea ice. Based upon unique samples collected within the Arctic Ocean during the polar night, we provide a new conceptual understanding of an intimate connection between these under-ice crustaceans and the deep Arctic Ocean currents. We suggest that downwards vertical migrations, followed by polewards transport in deep ocean currents, are an adaptive trait of ice fauna that both increases survival during ice-free periods of the year and enables re-colonization of sea ice when they ascend within the Arctic Ocean. From an evolutionary perspective, this may have been an adaptation allowing success in a seasonally ice-covered Arctic. Our findings may ultimately change the perception of ice fauna as a biota imminently threatened by the predicted disappearance of perennial sea ice.

Modeling seasonality of ice and ocean carbon production in the Arctic

NASA Astrophysics Data System (ADS)

Jin, M.; Deal, C. M.; Ji, R.

2011-12-01

In the Arctic Ocean, both phytoplankton and sea ice algae are important contributors to the primary production and the arctic food web. Copepod in the arctic regions have developed their feeding habit depending on the timing between the ice algal bloom and the subsequent phytoplankton bloom. A mismatch of the timing due to climate changes could have dramatic consequences on the food web as shown by some regional observations. In this study, a global coupled ice-ocean-ecosystem model was used to assess the seasonality of the ice algal and phytoplankton blooms in the arctic. The ice-ocean ecosystem modules are fully coupled in the physical model POP-CICE (Parallel Ocean Program- Los Alamos Sea Ice Model). The model results are compared with various observations. The modeled ice and ocean carbon production were analyzed by regions and their linkage to the physical environment changes (such as changes of ice concentration and water temperature, and light intensity etc.) between low- and high-ice years.

Predicting the Arctic Ocean Environment in the 21st century

NASA Astrophysics Data System (ADS)

Aksenov, Yevgeny; Popova, Ekaterina; Yool, Andrew; Nurser, George

2015-04-01

Recent environmental changes in the Arctic have clearly demonstrated that climate change is faster and more vigorously in the Polar Regions than anywhere else. Significantly, change in the Arctic Ocean (AO) environment presents a variety of impacts, from ecological to social-economic and political. Mitigation of this change and adaptation to it requires detailed and robust environmental predictions. Here we present a detailed projection of ocean circulation and sea ice from the present until 2099, based on an eddy-permitting high-resolution global simulation of the NEMO ¼ degree ocean model. The model is forced at the surface with HadGEM2-ES atmosphere model output from the UK Met. Office IPCC Assessment Report 5 (AR5) Representative Concentration Pathways 8.5 (RCP8.5) scenario. The HadGEM2-ES simulations span 1860-2099 and are one of an ensemble of runs performed for the Coupled Model Intercomparison Project 5 (CMIP5) and IPCC AR5. Between 2000-2009 and 2090-2099 the AO experiences a significant warming, with sea surface temperature increasing on average by about 4° C, particularly in the Barents and Kara Seas, and in the Greenland Sea and Hudson Bay. By the end of the simulation, Arctic sea ice has an average annual thickness of less than 10 cm in the central AO, and less than 0.5 m in the East-Siberian Sea and Canadian Archipelago, and disappears entirely during the Arctic summer. In summer, opening of large areas of the Arctic Ocean to the wind and surface waves leads to the Arctic pack ice cover evolving into the Marginal Ice Zone (MIZ). In winter, sea ice persists until the 2030s; then it sharply declines and disappears from the Central Arctic Ocean by the end of the 21st century, with MIZ provinces remaining in winter along the Siberian, Alaskan coasts and in the Canadian Arctic Archipelago. Analysis of the AO circulation reveals evidence of (i) the reversal of the Arctic boundary currents in the Canadian Basin, from a weak cyclonic current in 2040-2049 to

Increased fluxes of shelf-derived materials to the central Arctic Ocean

PubMed Central

Kipp, Lauren E.; Charette, Matthew A.; Moore, Willard S.; Henderson, Paul B.; Rigor, Ignatius G.

2018-01-01

Rising temperatures in the Arctic Ocean region are responsible for changes such as reduced ice cover, permafrost thawing, and increased river discharge, which, together, alter nutrient and carbon cycles over the vast Arctic continental shelf. We show that the concentration of radium-228, sourced to seawater through sediment-water exchange processes, has increased substantially in surface waters of the central Arctic Ocean over the past decade. A mass balance model for 228Ra suggests that this increase is due to an intensification of shelf-derived material inputs to the central basin, a source that would also carry elevated concentrations of dissolved organic carbon and nutrients. Therefore, we suggest that significant changes in the nutrient, carbon, and trace metal balances of the Arctic Ocean are underway, with the potential to affect biological productivity and species assemblages in Arctic surface waters. PMID:29326980

Current State and Recent Changes in the Arctic Ocean from the HYCOM-NCODA Global Ocean and Sea Ice Prediction System

NASA Astrophysics Data System (ADS)

Dukhovskoy, D. S.; Chassignet, E. P.; Hogan, P. J.; Metzger, E. J.; Posey, P.; Smedstad, O. M.; Stefanova, L. B.; Wallcraft, A. J.

2016-12-01

The great potential of numerical models to provide a high-resolution continuous picture of the environmental characteristics of the Arctic system is related to the problem of reliability and accuracy of the simulations. Recent Arctic Ocean model intercomparison projects have identified substantial disagreements in water mass distribution and circulation among the models over the last two decades. In situ and satellite observations cannot yield enough continuous in time and space information to interpret the observed changes in the Arctic system. Observations combined with Arctic Ocean models via data assimilation provide perhaps the most complete knowledge about the state of the Arctic system. We use outputs from the US Navy Global Ocean Forecast System (20-year reanalysis + analysis) to investigate several hypotheses that have been put forward regarding the current state and recent changes in the Arctic Ocean. The system is based on the 0.08-degree HYbrid Coordinate Ocean Model (HYCOM) and can be run with two-way coupling to the Los Alamos Community Ice CodE (CICE) or with an energy-loan ice model. Observations are assimilated by the Navy Coupled Ocean Data Assimilation (NCODA) algorithm. HYCOM temperature and salinity fields are shown to be in good agreement with observational data in the Arctic and North Atlantic. The model reproduces changes in the freshwater budget in the Arctic as reported in other studies. The modeled freshwater fluxes between the Arctic Ocean and the North Atlantic are analyzed to document and discuss the interaction between the two regions over the last two decades.

Organophosphate Ester Flame Retardants and Plasticizers in Ocean Sediments from the North Pacific to the Arctic Ocean.

PubMed

Ma, Yuxin; Xie, Zhiyong; Lohmann, Rainer; Mi, Wenying; Gao, Guoping

2017-04-04

The presence of organophosphate ester (OPE) flame retardants and plasticizers in surface sediment from the North Pacific to Arctic Ocean was observed for the first time during the fourth National Arctic Research Expedition of China in the summer of 2010. The samples were analyzed for three halogenated OPEs [tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), and tris(dichloroisopropyl) phosphate], three alkylated OPEs [triisobutyl phosphate (TiBP), tri-n-butyl phosphate, and tripentyl phosphate], and triphenyl phosphate. Σ 7 OPEs (total concentration of the observed OPEs) was in the range of 159-4658 pg/g of dry weight. Halogenated OPEs were generally more abundant than the nonhalogenated OPEs; TCEP and TiBP dominated the overall concentrations. Except for that of the Bering Sea, Σ 7 OPEs values increased with increasing latitudes from Bering Strait to the Central Arctic Ocean, while the contributions of halogenated OPEs (typically TCEP and TCPP) to the total OPE profile also increased from the Bering Strait to the Central Arctic Ocean, indicating they are more likely to be transported to the remote Arctic. The median budget of 52 (range of 17-292) tons for Σ 7 OPEs in sediment from the Central Arctic Ocean represents only a very small amount of their total production volume, yet the amount of OPEs in Arctic Ocean sediment was significantly larger than the sum of polybrominated diphenyl ethers (PBDEs) in the sediment, indicating they are equally prone to long-range transport away from source regions. Given the increasing level of production and usage of OPEs as substitutes of PBDEs, OPEs will continue to accumulate in the remote Arctic.

Acquiring Marine Data in the Canada Basin, Arctic Ocean

NASA Astrophysics Data System (ADS)

Hutchinson, Deborah R.; Jackson, H. Ruth; Shimeld, John W.; Chapman, C. Borden; Childs, Jonathan R.; Funck, Thomas; Rowland, Robert W.

2009-06-01

Despite the record minimum ice extent in the Arctic Ocean for the past 2 years, collecting geophysical data with towed sensors in ice-covered regions continues to pose enormous challenges. Significant parts of the Canada Basin in the western Arctic Ocean have remained largely unmapped because thick multiyear ice has limited access even by research vessels strengthened against ice [Jackson et al., 1990]. Because of the resulting paucity of data, the western Arctic Ocean is one of the few areas of ocean in the world where major controversies still exist with respect to its origin and tectonic evolution [Grantz et al., 1990; Lawver and Scotese, 1990; Lane, 1997; Miller et al., 2006]. This article describes the logistical challenges and initial data sets from geophysical seismic reflection, seismic refraction, and hydrographic surveys in the Canada Basin conducted by scientists with U.S. and Canadian government agencies (Figure 1a) to fulfill the requirements of the United Nations Convention on the Law of the Sea to determine sediment thickness, geological origin, and basin evolution in this unexplored part of the world. Some of these data were collected using a single ship, but the heaviest ice conditions necessitated using two icebreakers, similar to other recent Arctic surveys [e.g., Jokat, 2003].

Influences of Ocean Thermohaline Stratification on Arctic Sea Ice

NASA Astrophysics Data System (ADS)

Toole, J. M.; Timmermans, M.-L.; Perovich, D. K.; Krishfield, R. A.; Proshutinsky, A.; Richter-Menge, J. A.

2009-04-01

The Arctic Ocean's surface mixed layer constitutes the dynamical and thermodynamical link between the sea ice and the underlying waters. Wind stress, acting directly on the surface mixed layer or via wind-forced ice motion, produce surface currents that can in turn drive deep ocean flow. Mixed layer temperature is intimately related to basal sea ice growth and melting. Heat fluxes into or out of the surface mixed layer can occur at both its upper and lower interfaces: the former via air-sea exchange at leads and conduction through the ice, the latter via turbulent mixing and entrainment at the layer base. Variations in Arctic Ocean mixed layer properties are documented based on more than 16,000 temperature and salinity profiles acquired by Ice-Tethered Profilers since summer 2004 and analyzed in conjunction with sea ice observations from Ice Mass Balance Buoys and atmospheric heat flux estimates. Guidance interpreting the observations is provided by a one-dimensional ocean mixed layer model. The study focuses attention on the very strong density stratification about the mixed layer base in the Arctic that, in regions of sea ice melting, is increasing with time. The intense stratification greatly impedes mixed layer deepening by vertical convection and shear mixing, and thus limits the flux of deep ocean heat to the surface that could influence sea ice growth/decay. Consistent with previous work, this study demonstrates that the Arctic sea ice is most sensitive to changes in ocean mixed layer heat resulting from fluxes across its upper (air-sea and/or ice-water) interface.

Changes in Ocean Circulation with an Ice-Free Arctic: Reconstructing Early Holocene Arctic Ocean Circulation Using Geochemical Signals from Individual Neogloboquadrina pachyderma (sinistral) Shells

NASA Astrophysics Data System (ADS)

Livsey, C.; Spero, H. J.; Kozdon, R.

2016-12-01

The impacts of sea ice decrease and consequent hydrologic changes in the Arctic Ocean will be experienced globally as ocean and atmospheric temperatures continue to rise, though it is not evident to what extent. Understanding the structure of the Arctic water column during the early/mid Holocene sea ice minimum ( 6-10 kya), a post-glacial analogue of a seasonally ice-free Arctic, will help us to predict what the changes we can expect as the Earth warms over the next century. Neogloboquadrina pachyderma (sinistral; Nps) is a species of planktonic foraminifera that dominates assemblages in the polar oceans. This species grows its chambers (ontogenetic calcite) in the surface waters and subsequently descends through the water column to below the mixed layer where it quickly adds a thick crust of calcite (Kohfeld et al., 1996). Therefore, geochemical signals from both the surface waters and sub-mixed layer depths are captured within single Nps shells. We were able to target <5 μm - sized domains for δ18O using secondary ion mass spectrometry (SIMS), therefore capturing signals from both the ontogenetic and crust calcite in single Nps shells. This data was combined with laser ablation- inductively coupled mass spectrometry (LA-ICPMS) Mg/Ca profiles of trace metals through the two layers of calcite of the same shells, to determine the thermal structure of the water column. Combining δ18O, temperature, and salinity gradients from locations across the Arctic basin allow us to reconstruct the hydrography of the early Holocene Arctic sea ice minimum. These results will be compared with modern Arctic water column characteristics in order to develop a conceptual model of Arctic Ocean oceanographic change due to global warming. Kohfeld, K.E., Fairbanks, R.G., Smith, S.L., Walsh, I.D., 1996. Neogloboquadrina pachyderma(sinistral coiling) as paleoceanographic tracers in polar oceans: Evidence from northeast water polynya plankton tows, sediment traps, and surface sediments

Global View of the Arctic Ocean

NASA Image and Video Library

2000-09-20

NASA researchers have new [sic] insights into the mysteries of Arctic sea ice, thanks to the unique abilities of Canada's Radarsat satellite. The Arctic is the smallest of the world's four oceans, but it may play a large role in helping scientists monitor Earth's climate shifts. Using Radarsat's special sensors to take images at night and to peer through clouds, NASA researchers can now see the complete ice cover of the Arctic. This allows tracking of any shifts and changes, in unprecedented detail, over the course of an entire winter. The radar-generated, high-resolution images are up to 100 times better than those taken by previous satellites. http://photojournal.jpl.nasa.gov/catalog/PIA02970

Dissolved Organic Matter Land-Ocean Linkages in the Arctic

NASA Astrophysics Data System (ADS)

Mann, P. J.; Spencer, R. M.; Hernes, P. J.; Tank, S. E.; Striegl, R.; Dyda, R. Y.; Peterson, B. J.; McClelland, J. W.; Holmes, R. M.

2012-04-01

Rivers draining into the Arctic Ocean exhibit high concentrations of terrigenous dissolved organic carbon (DOC), and recent studies indicate that DOC export is changing due to climatic warming and alteration in permafrost condition. The fate of exported DOC in the Arctic Ocean is important for understanding the regional carbon cycle and remains a point of discussion in the literature. As part of the NSF funded Arctic Great Rivers Observatory (Arctic-GRO) project, samples were collected for DOC, chromophoric and fluorescent dissolved organic matter (CDOM & FDOM) and lignin phenols from the Ob', Yenisey, Lena, Kolyma, Mackenzie and Yukon rivers in 2009 - 2010. DOC and lignin concentrations were elevated during the spring freshet and measurements related to DOC composition indicated an increasing contribution from terrestrial vascular plant sources at this time of year (e.g. lignin carbon-normalized yield, CDOM spectral slope, SUVA254, humic-like fluorescence). CDOM absorption was found to correlate strongly with both DOC (r2=0.83) and lignin concentration (r2=0.92) across the major arctic rivers. Lignin composition was also successfully modeled using FDOM measurements decomposed using PARAFAC analysis. Utilizing these relationships we modeled loads for DOC and lignin export from high-resolution CDOM measurements (daily across the freshet) to derive improved flux estimates, particularly from the dynamic spring discharge maxima period when the majority of DOC and lignin export occurs. The new load estimates for DOC and lignin are higher than previous evaluations, emphasizing that if these are more representative of current arctic riverine export, terrigenous DOC is transiting through the Arctic Ocean at a faster rate than previously thought. It is apparent that higher resolution sampling of arctic rivers is exceptionally valuable with respect to deriving accurate fluxes and we highlight the potential of CDOM in this role for future studies and the applicability of in

Arctic Ocean Sedimentary Cover Structure, Based on 2D MCS Seismic Data.

NASA Astrophysics Data System (ADS)

Kireev, A.; Kaminsky, V.; Poselov, V.; Poselova, L.; Kaminsky, D.

2016-12-01

In 2016 the Russian Federation has submitted its partial revised Submission for establishment of the OLCS (outer limit of the continental shelf) in the Arctic Ocean. In order to prepare the Submission, in 2005 - 2014 the Russian organizations carried out a wide range of geological and geophysical studies, so that today over 23000 km of MCS lines and 4000 km of deep seismic sounding are accomplished. For correct time/depth conversion of seismic sections obtained with a short streamer in difficult ice conditions wide-angle reflection/refraction seismic sonobuoy soundings were used. All of these seismic data were used to refine the stratigraphy model, to identify sedimentary complexes and to estimate the total thickness of the sedimentary cover. Seismic stratigraphy model was successively determined for the Cenozoic and pre-Cenozoic parts of the sedimentary section and was based on correlation of the Russian MCS data and seismic data documented by boreholes. Cenozoic part of the sedimentary cover is based on correlation of the Russian MCS data and AWI91090 section calibrated by ACEX-2004 boreholes on the Lomonosov Ridge for Amerasia basin and by correlation of onlap contacts onto oceanic crust with defined magnetic anomalies for Eurasia basin. Pre-Cenozoic part of the sedimentary cover is based on tracing major unconformities from boreholes on the Chukchi shelf (Crackerjack, Klondike, Popcorn) to the North-Chuckchi Trough and further to the Mendeleev Rise as well as to the Vilkitsky Trough and the adjacent Podvodnikov Basin. Six main unconformities were traced: regional unconformity (RU), Eocene unconformity (EoU) (for Eurasia basin only), post-Campanian unconformity (pCU), Brookian (BU - base of the Lower Brookian unit), Lower Cretaceous (LCU) and Jurassic (JU - top of the Upper Ellesmerian unit). The final step in our research was to generalize all seismic surveys (top of acoustic basement correlation data) and bathymetry data in the sedimentary cover thickness map

Improved ocean-color remote sensing in the Arctic using the POLYMER algorithm

NASA Astrophysics Data System (ADS)

Frouin, Robert; Deschamps, Pierre-Yves; Ramon, Didier; Steinmetz, François

2012-10-01

Atmospheric correction of ocean-color imagery in the Arctic brings some specific challenges that the standard atmospheric correction algorithm does not address, namely low solar elevation, high cloud frequency, multi-layered polar clouds, presence of ice in the field-of-view, and adjacency effects from highly reflecting surfaces covered by snow and ice and from clouds. The challenges may be addressed using a flexible atmospheric correction algorithm, referred to as POLYMER (Steinmetz and al., 2011). This algorithm does not use a specific aerosol model, but fits the atmospheric reflectance by a polynomial with a non spectral term that accounts for any non spectral scattering (clouds, coarse aerosol mode) or reflection (glitter, whitecaps, small ice surfaces within the instrument field of view), a spectral term with a law in wavelength to the power -1 (fine aerosol mode), and a spectral term with a law in wavelength to the power -4 (molecular scattering, adjacency effects from clouds and white surfaces). Tests are performed on selected MERIS imagery acquired over Arctic Seas. The derived ocean properties, i.e., marine reflectance and chlorophyll concentration, are compared with those obtained with the standard MEGS algorithm. The POLYMER estimates are more realistic in regions affected by the ice environment, e.g., chlorophyll concentration is higher near the ice edge, and spatial coverage is substantially increased. Good retrievals are obtained in the presence of thin clouds, with ocean-color features exhibiting spatial continuity from clear to cloudy regions. The POLYMER estimates of marine reflectance agree better with in situ measurements than the MEGS estimates. Biases are 0.001 or less in magnitude, except at 412 and 443 nm, where they reach 0.005 and 0.002, respectively, and root-mean-squared difference decreases from 0.006 at 412 nm to less than 0.001 at 620 and 665 nm. A first application to MODIS imagery is presented, revealing that the POLYMER algorithm is

Evaporative fractionation of marine water isotopes in the Arctic Ocean help understand a changing Arctic water cycle

NASA Astrophysics Data System (ADS)

Klein, E. S.; Welker, J. M.

2017-12-01

Most of the global hydrologic cycle occurs in oceanic waters. This oceanic derived moisture is critical to the precipitation and evapotranspiration regimes that influence terrestrial Earth systems. Thus understanding oceanic water processes has important global implications for our knowledge of modern and past hydrologic cycles. As they are influenced by environmental variables such as sea surface temperature and atmospheric humidity, water isotope ratios (e.g., δ18O, δ2H) can help understand the patterns driving the water cycle. However, our knowledge of marine isotopes is relatively limited. In particular, the fractionation of water isotopes during evaporation of oceanic water, essentially the start of the hydrologic cycle, is largely based on theoretical relationships derived from spatially and temporally limited data sets. This constrained understanding of oceanic evaporation fractionation patterns is especially pronounced in the rapidly changing Arctic Ocean. These changes are associated with reduced sea ice coverage, which is increasing the amount of local Artic Ocean sourced moisture in atmospheric and terrestrial systems and amplifying the Arctic hydrologic cycle. Here we present new data revealing the nuances of evaporative fractionation of Arctic Ocean water isotopes with the first collection of continuous, contemporaneous sea water and vapor isotopes. These data, collected in situ aboard the icebreaker Healy, show that the difference between actual ocean vapor isotope values and vapor values estimated by the closure equation increases progressively with latitude (especially beyond 70°) and varies between δ18O and δ2H. These differences are likely due to more isotopic mixing in the troposphere and/or closure equation assumptions inapplicable to Arctic regions. Moreover, we find: 1) a positive relationship between fractionation magnitude and latitude; and 2) the influence of evaporative fractionation from environmental variables such as wind and

Expanded record of Quaternary oceanographic change: Amerasian Arctic Ocean

USGS Publications Warehouse

Ishman, S.E.; Polyak, L.V.; Poore, R.Z.

1996-01-01

Four sediment cores collected from the Northwind and Mendeleyev ridges, Arctic Ocean, from 1089 m to 1909 m water depth, provide an oceanographic record extending back into the Matuyama reversed polarity chron. Benthic foraminiferal analyses show four prominent assemblage zones: Bolivina arctica, Cassidulina teretis, Bulimina aculeata, and Oridorsalis tener from the upper Matuyama reversed polarity chronozone through the Brunhes normal polarity chronozone. These assemblage zones represent depth-dependent benthic foraminiferal biofacies changes associated with oceanographic events that occurred in the Amerasian basin at ??? 780 and 300 ka, and indicate oceanographic influence from the North Atlantic. Recognition of these benthic assemblage zones in Arctic cores from the Alpha Ridge indicates that the benthic foraminiferal zonations in intermediate to deep water (>1000 m) Arctic cores may be more useful than preexisting lithostratigraphic zonations and should provide important information pertaining to the Quaternary paleoceanographic evolution of the Arctic Ocean.

Radiocesium in the western subarctic area of the North Pacific Ocean, Bering Sea, and Arctic Ocean in 2013 and 2014.

PubMed

Kumamoto, Yuichiro; Aoyama, Michio; Hamajima, Yasunori; Nishino, Shigeto; Murata, Akihiko; Kikuchi, Takashi

2017-08-01

We measured radiocesium ( 134 Cs and 137 Cs) in seawater from the western subarctic area of the North Pacific Ocean, Bering Sea, and Arctic Ocean in 2013 and 2014. Fukushima-derived 134 Cs in surface seawater was observed in the western subarctic area and Bering Sea but not in the Arctic Ocean. Vertical profile of 134 Cs in the Canada Basin of the Arctic Ocean implies that Fukushima-derived 134 Cs intruded into the basin from the Bering Sea through subsurface (150m depth) in 2014. Copyright © 2017 Elsevier Ltd. All rights reserved.

Arctic Deep Water Ferromanganese-Oxide Deposits Reflect the Unique Characteristics of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Hein, James R.; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe J.; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah R.; Till, Claire P.

2017-11-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, and HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits. The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ˜15 Myr ago.

Arctic deep-water ferromanganese-oxide deposits reflect the unique characteristics of the Arctic Ocean

USGS Publications Warehouse

Hein, James; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah; Till, Claire P.

2017-01-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits.The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ∼15 Myr ago.

Satellite surface salinity maps to determine fresh water fluxes in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Gabarro, Carolina; Estrella, Olmedo; Emelianov, Mikhail; Ballabrera, Joaquim; Turiel, Antonio

2017-04-01

Salinity and temperature gradients drive the thermohaline circulation of the oceans, and play a key role in the ocean-atmosphere coupling. The strong and direct interactions between the ocean and the cryosphere (primarily through sea ice and ice shelves) are also a key ingredient of the thermohaline circulation. Recent observational studies have documented changes in upper Arctic Ocean hydrography [1, 2]. The ESA's Soil Moisture and Ocean Salinity (SMOS) mission, launched in 2009, have the objective to measure soil moisture over the continents and sea surface salinity over the oceans [3]. However, SMOS is also making inroads in Cryospheric science, as the measurements of thin ice thickness and sea ice concentration. SMOS carries an innovative L-band (1.4 GHz, or 21-cm wavelength), passive interferometric radiometer (the so-called MIRAS) that measures the electromagnetic radiation emitted by the Earth's surface, at about 50 km spatial resolution wide swath (1200-km), and with a 3-day revisit time at the equator, but more frequently at the poles. Although the SMOS radiometer operating frequency offers almost the maximum sensitivity of the brightness temperature (TB) to sea surface salinity (SSS) variations, such sensitivity is rather low, even lower at cold waters [4]: 90% of ocean SSS values span a range of brightness temperatures of just 5K. This implies that the SMOS SSS retrieval requires a high performance of the MIRAS interferometric radiometer [5]. New algorithms, recently developed at the Barcelona Expert Center (BEC) to improve the quality of SMOS measurements [6], allow for the first time to derive cold-water SSS maps from SMOS data, and to observe the variability of the SSS in the higher north Atlantic and the Arctic Ocean. In this work, we will provide an assessment of the quality of these new SSS Arctic maps, and we will illustrate their potential to monitor the impact on ocean state of the discharges from the main rivers to the Arctic Ocean. Moreover

Global View of the Arctic Ocean

NASA Technical Reports Server (NTRS)

2000-01-01

NASA researchers have new insights into the mysteries of Arctic sea ice, thanks to the unique abilities of Canada's Radarsat satellite. The Arctic is the smallest of the world's four oceans, but it may play a large role in helping scientists monitor Earth's climate shifts.

Using Radarsat's special sensors to take images at night and to peer through clouds, NASA researchers can now see the complete ice cover of the Arctic. This allows tracking of any shifts and changes, in unprecedented detail, over the course of an entire winter. The radar-generated, high-resolution images are up to 100 times better than those taken by previous satellites.

Using this new information, scientists at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., can generate comprehensive maps of Arctic sea ice thickness for the first time. 'Before we knew only the extent of the ice cover,' said Dr. Ronald Kwok, JPL principal investigator of a project called Sea Ice Thickness Derived From High Resolution Radar Imagery. 'We also knew that the sea ice extent had decreased over the last 20 years, but we knew very little about ice thickness.'

'Since sea ice is very thin, about 3 meters (10 feet) or less,'Kwok explained, 'it is very sensitive to climate change.'

Until now, observations of polar sea ice thickness have been available for specific areas, but not for the entire polar region.

The new radar mapping technique has also given scientists a close look at how the sea ice cover grows and contorts over time. 'Using this new data set, we have the first estimates of how much ice has been produced and where it formed during the winter. We have never been able to do this before, ' said Kwok. 'Through our radar maps of the Arctic Ocean, we can actually see ice breaking apart and thin ice growth in the new openings. '

RADARSAT gives researchers a piece of the overall puzzle every three days by creating a complete image of the Arctic. NASA scientists then put those puzzle pieces

Patterns and controlling factors of species diversity in the Arctic Ocean

USGS Publications Warehouse

Yasuhara, Moriaki; Hunt, Gene; van Dijken, Gert; Arrigo, Kevin R.; Cronin, Thomas M.; Wollenburg, Jutta E.

2012-01-01

Aim  The Arctic Ocean is one of the last near-pristine regions on Earth, and, although human activities are expected to impact on Arctic ecosystems, we know very little about baseline patterns of Arctic Ocean biodiversity. This paper aims to describe Arctic Ocean-wide patterns of benthic biodiversity and to explore factors related to the large-scale species diversity patterns.Location  Arctic Ocean.Methods  We used large ostracode and foraminiferal datasets to describe the biodiversity patterns and applied comprehensive ecological modelling to test the degree to which these patterns are potentially governed by environmental factors, such as temperature, productivity, seasonality, ice cover and others. To test environmental control of the observed diversity patterns, subsets of samples for which all environmental parameters were available were analysed with multiple regression and model averaging.Results  Well-known negative latitudinal species diversity gradients (LSDGs) were found in metazoan Ostracoda, but the LSDGs were unimodal with an intermediate maximum with respect to latitude in protozoan foraminifera. Depth species diversity gradients were unimodal, with peaks in diversity shallower than those in other oceans. Our modelling results showed that several factors are significant predictors of diversity, but the significant predictors were different among shallow marine ostracodes, deep-sea ostracodes and deep-sea foraminifera.Main conclusions  On the basis of these Arctic Ocean-wide comprehensive datasets, we document large-scale diversity patterns with respect to latitude and depth. Our modelling results suggest that the underlying mechanisms causing these species diversity patterns are unexpectedly complex. The environmental parameters of temperature, surface productivity, seasonality of productivity, salinity and ice cover can all play a role in shaping large-scale diversity patterns, but their relative importance may depend on the ecological

Aragonite undersaturation in the Arctic Ocean: effects of ocean acidification and sea ice melt.

PubMed

Yamamoto-Kawai, Michiyo; McLaughlin, Fiona A; Carmack, Eddy C; Nishino, Shigeto; Shimada, Koji

2009-11-20

The increase in anthropogenic carbon dioxide emissions and attendant increase in ocean acidification and sea ice melt act together to decrease the saturation state of calcium carbonate in the Canada Basin of the Arctic Ocean. In 2008, surface waters were undersaturated with respect to aragonite, a relatively soluble form of calcium carbonate found in plankton and invertebrates. Undersaturation was found to be a direct consequence of the recent extensive melting of sea ice in the Canada Basin. In addition, the retreat of the ice edge well past the shelf-break has produced conditions favorable to enhanced upwelling of subsurface, aragonite-undersaturated water onto the Arctic continental shelf. Undersaturation will affect both planktonic and benthic calcifying biota and therefore the composition of the Arctic ecosystem.

The phenology of Arctic Ocean surface warming.

PubMed

Steele, Michael; Dickinson, Suzanne

2016-09-01

In this work, we explore the seasonal relationships (i.e., the phenology) between sea ice retreat, sea surface temperature (SST), and atmospheric heat fluxes in the Pacific Sector of the Arctic Ocean, using satellite and reanalysis data. We find that where ice retreats early in most years, maximum summertime SSTs are usually warmer, relative to areas with later retreat. For any particular year, we find that anomalously early ice retreat generally leads to anomalously warm SSTs. However, this relationship is weak in the Chukchi Sea, where ocean advection plays a large role. It is also weak where retreat in a particular year happens earlier than usual, but still relatively late in the season, primarily because atmospheric heat fluxes are weak at that time. This result helps to explain the very different ocean warming responses found in two recent years with extreme ice retreat, 2007 and 2012. We also find that the timing of ice retreat impacts the date of maximum SST, owing to a change in the ocean surface buoyancy and momentum forcing that occurs in early August that we term the Late Summer Transition (LST). After the LST, enhanced mixing of the upper ocean leads to cooling of the ocean surface even while atmospheric heat fluxes are still weakly downward. Our results indicate that in the near-term, earlier ice retreat is likely to cause enhanced ocean surface warming in much of the Arctic Ocean, although not where ice retreat still occurs late in the season.

Arctic Ocean Tides from GRACE Satellite Accelerations

NASA Astrophysics Data System (ADS)

Killett, B.; Wahr, J. M.; Desai, S. D.; Yuan, D.; Watkins, M. M.

2010-12-01

Because missions such as TOPEX/POSEIDON don't extend to high latitudes, Arctic ocean tidal solutions aren't constrained by altimetry data. The resulting errors in tidal models alias into monthly GRACE gravity field solutions at all latitudes. Fortunately, GRACE inter-satellite ranging data can be used to solve for these tides directly. Seven years of GRACE inter-satellite acceleration data are inverted using a mascon approach to solve for residual amplitudes and phases of major solar and lunar tides in the Arctic ocean relative to FES 2004. Simulations are performed to test the inversion algorithm's performance, and uncertainty estimates are derived from the tidal signal over land. Truncation error magnitudes and patterns are compared to the residual tidal signals.

Critical Metals In Western Arctic Ocean Ferromanganese Mineral Deposits

NASA Astrophysics Data System (ADS)

Hein, J. R.; Spinardi, F.; Conrad, T. A.; Conrad, J. E.; Genetti, J.

2013-12-01

Little exploration for minerals has occurred in the Arctic Ocean due to ice cover and the remote location. Small deposits of seafloor massive sulfides that are rich in copper and zinc occur on Gakkel Ridge, which extends from Greenland to the Laptev Sea, and on Kolbeinsey and Mohns ridges, both located between Greenland and mainland Europe. However, rocks were recently collected by dredge along the western margin of the Canada Basin as part of the U.S. Extended Continental Shelf (ECS) program north of Alaska. Sample sites include steep escarpments on the Chukchi Borderland, a newly discovered seamount informally named Healy seamount, the southern part of Alpha-Mendeleev Ridge, and several basement outcrops in Nautilus Basin. These dredge hauls yielded three types of metal-rich mineralized deposits: ferromanganese crusts, ferromanganese nodules, and hydrothermal iron and manganese deposits. Chemical analyses of 43 crust and nodule samples show high contents of many critical metals needed for high-technology, green-technology, and energy and military applications, including cobalt (to 0.3 wt.%), vanadium (to 0.12 wt.%), zirconium (to 459 grams/tonne=ppm), molybdenum (to 453 g/t), the rare-earth elements (including scandium and yttrium; yttrium to 229 g/t), lithium (to 205 g/t), tungsten (to 64 g/t), and gallium (to 26 g/t). The metal contents of these Arctic Ocean crusts and nodules are comparable to those found throughout the global ocean, however, these Arctic Ocean samples are the first that have been found to be enriched in rare metal scandium. The metal contents of these samples indicate a diagenetic component. Crusts typically form by precipitation of metal oxides solely from seawater (hydrogenetic) onto rock surfaces producing a pavement, whereas nodules form by accretion of metal oxides, from both seawater and pore waters (diagenetic), around a nucleus on the surface of soft sediment. The best evidence for this diagenetic input to the crusts is that crusts

Towards an Ice-Free Arctic Ocean in Summertime

NASA Astrophysics Data System (ADS)

Gascard, Jean Claude

2014-05-01

Dividing the Arctic Ocean in two parts, the so-called Atlantic versus the Pacific sector, two distinct modes of variability appear for characterizing the Arctic sea-ice extent from 70°N up to 80°N in both sectors. The Atlantic sector seasonal sea-ice extent is characterized by a longer time scale than the Pacific sector with a break up melting season starting in May and reaching a peak in June-July, one month earlier than the Pacific sector of the Arctic Ocean revealing a faster time evolution and a larger spatial amplitude than the Atlantic sector. During recent years like 2007, sea-ice extent with sea-ice concentration above 15% retreated from 4 millions km2 to about 1 million km2 in the Arctic Pacific sector between 70° and 80°N except for 2012 when most of sea-ice melted away in this region. That explained most of the differences between the two extreme years 2007 and 2012. In the Atlantic sector, Arctic sea-ice retreated from 2 millions km2 to nearly 0 during recent years including 2007 and 2012. The Atlantic inflow North of Svalbard and Franz Josef Land is more likely responsible for a northward retreat of the ice edge in that region. The important factor is not only that the Arctic summer sea-ice minimum extent decreased by 3 or 4 millions km2 over the past 10 years but also that the melting period was steadily increasing by one to two days every year during that period. An important factor concerns the strength of the freezing that can be quantified in terms of Freezing Degree Days FDD accumulated during the winter-spring season and the strength of the melting (MDD) that can be accumulated during the summer season. FDD and MDD have been calculated for the past 30 years all over the Arctic Ocean using ERA Interim Reanalysis surface temperature at 2m height in the atmosphere. It is clear that FDD decreased significantly by more than 2000 FDD between 1980 and 2012 which is equivalent to the sensible heat flux corresponding to more than a meter of sea

Cruise to the Chukchi Borderland, Arctic Ocean

USGS Publications Warehouse

Grantz, Arthur; ,

1993-01-01

Oceanography and geology were the principal focuses of the U.S. Geological Survey-sponsored expedition Arctic Summer West '92, which traveled to the eastern part of the Chukchi Borderland of the Amerasia Basin, western Arctic Ocean. The expedition took place from August 20 to September 25, 1992, aboard the Coast Guard cutter Polar Star. USGS investigated the geologic framework and tectonic origin of the borderland, Arctic Quaternary paleoclimate, sea-ice transport of particulate matter in the Beaufort Gyre, and possible radionuclide contamination of the water column and seafloor off Alaska from sources in the Russian Arctic. Researchers from five other institutions studied the area's oceanography, age of the water column, paleoenvironment of the Holocene sediment, physical properties and synthetic-aperture radar backscatter of sea ice, and the drop-stone content of late Quaternary sediment.

Spatial Distributions of DDTs in the Water Masses of the Arctic Ocean.

PubMed

Carrizo, Daniel; Sobek, Anna; Salvadó, Joan A; Gustafsson, Örjan

2017-07-18

There is a scarcity of data on the amount and distribution of the organochlorine pesticide dichlorodiphenyltrichloroethane (DDT) and its metabolites in intermediate and deep ocean water masses. Here, the distribution and inventories of DDTs in water of the Arctic shelf seas and the interior basin are presented. The occurrence of ∑ 6 DDT (0.10-66 pg L -1 ) in the surface water was dominated by 4,4'-DDE. In the Central Arctic Ocean increasing concentrations of DDE with depth were observed in the Makarov and Amundsen basins. The increasing concentrations down to 2500 m depth is in accordance with previous findings for PCBs and PBDEs. Similar concentrations of DDT and DDEs were found in the surface water, while the relative contribution of DDEs increased with depth, demonstrating a transformation over time and depth. Higher concentrations of DDTs were found in the European part of the Arctic Ocean; these distributions likely reflect a combination of different usage patterns, transport, and fate of these compounds. For instance, the elevated concentrations of DDTs in the Barents and Atlantic sectors of the Arctic Ocean indicate the northbound Atlantic current as a significant conveyor of DDTs. This study contributes to the very rare data on OCPs in the vast deep-water compartments and combined with surface water distribution across the Arctic Ocean helps to improve our understanding of the large-scale fate of DDTs in the Arctic.

Diurnal tides in the Arctic Ocean

NASA Technical Reports Server (NTRS)

Kowalik, Z.; Proshutinsky, A. Y.

1993-01-01

A 2D numerical model with a space grid of about 14 km is applied to calculate diurnal tidal constituents K(1) and O(1) in the Arctic Ocean. Calculated corange and cotidal charts show that along the continental slope, local regions of increased sea level amplitude, highly variable phase and enhanced currents occur. It is shown that in these local regions, shelf waves (topographic waves) of tidal origin are generated. In the Arctic Ocean and Northern Atlantic Ocean more than 30 regions of enhanced currents are identified. To prove the near-resonant interaction of the diurnal tides with the local bottom topography, the natural periods of oscillations for all regions have been calculated. The flux of energy averaged over the tidal period depicts the gyres of semitrapped energy, suggesting that the shelf waves are partially trapped over the irregularities of the bottom topography. It is shown that the occurrence of near-resonance phenomenon changes the energy flow in the tidal waves. First, the flux of energy from the astronomical sources is amplified in the shelf wave regions, and afterwards the tidal energy is strongly dissipated in the same regions.

Arctic polynya and glacier interactions

NASA Astrophysics Data System (ADS)

Edwards, Laura

2013-04-01

Major uncertainties surround future estimates of sea level rise attributable to mass loss from the polar ice sheets and ice caps. Understanding changes across the Arctic is vital as major potential contributors to sea level, the Greenland Ice Sheet and the ice caps and glaciers of the Canadian Arctic archipelago, have experienced dramatic changes in recent times. Most ice mass loss is currently focused at a relatively small number of glacier catchments where ice acceleration, thinning and calving occurs at ocean margins. Research suggests that these tidewater glaciers accelerate and iceberg calving rates increase when warming ocean currents increase melt on the underside of floating glacier ice and when adjacent sea ice is removed causing a reduction in 'buttressing' back stress. Thus localised changes in ocean temperatures and in sea ice (extent and thickness) adjacent to major glacial catchments can impact hugely on the dynamics of, and hence mass lost from, terrestrial ice sheets and ice caps. Polynyas are areas of open water within sea ice which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~50,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas play a vital role in the heat balance of the polar oceans and strongly impact regional oceanography. Where polynyas develop adjacent to tidewater glaciers their influence on ocean circulation and water temperatures may play a major part in controlling subsurface ice melt rates by impacting on the water masses reaching the calving front. Areas of open water also play a significant role in controlling the potential of the atmosphere to carry moisture, as well as allowing heat exchange between the atmosphere and ocean, and so can influence accumulation on (and hence thickness of) glaciers and ice caps. Polynya presence and size also has implications for sea ice extent and therefore potentially the buttressing effect on neighbouring

Sensitivity of the Arctic Ocean gas hydrate to climate changes in the period of 1948-2015

NASA Astrophysics Data System (ADS)

Malakhova, Valentina V.; Golubeva, Elena N.; Iakshina, Dina F.

2017-11-01

The objective of the present study is to analyze the interactions between a methane hydrates stability zone and the ocean temperature variations and to define the hydrate sensitivity to the contemporary warming in the Arctic Ocean. To obtain the spatial-temporary variability of the ocean bottom temperature we employ the ICMMG regional Arctic-North Atlantic ocean model that has been developed in the Institute of Computational Mathematics and Mathematical Geophysics. With the ice-ocean model the Arctic bottom water temperatures were analyzed. The resulting warming ocean bottom water is spatially inhomogeneous, with a strong impact by the Atlantic inflow on shallow regions of 200-500 m depth. Results of the mathematical modeling of the dynamics of methane hydrate stability zone in the Arctic Ocean sediment are reported. We find that the reduction of the methane hydrate stability zone occurs in the Arctic Ocean between 250 and 400 m water depths within the upper 100 m of sediment in the area influenced by the Atlantic inflow. We have identified the areas of the Arctic Ocean where an increase in methane release is probable to occur at the present time.

Impacts of ocean albedo alteration on Arctic sea ice restoration and Northern Hemisphere climate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cvijanovic, Ivana; Caldeira, Ken; MacMartin, Douglas G.

The Arctic Ocean is expected to transition into a seasonally ice-free state by mid-century, enhancing Arctic warming and leading to substantial ecological and socio-economic challenges across the Arctic region. It has been proposed that artificially increasing high latitude ocean albedo could restore sea ice, but the climate impacts of such a strategy have not been previously explored. Motivated by this, we investigate the impacts of idealized high latitude ocean albedo changes on Arctic sea ice restoration and climate. In our simulated 4xCO₂ climate, imposing surface albedo alterations over the Arctic Ocean leads to partial sea ice recovery and a modestmore » reduction in Arctic warming. With the most extreme ocean albedo changes, imposed over the area 70°–90°N, September sea ice cover stabilizes at ~40% of its preindustrial value (compared to ~3% without imposed albedo modifications). This is accompanied by an annual mean Arctic surface temperature decrease of ~2 °C but no substantial global mean temperature decrease. Imposed albedo changes and sea ice recovery alter climate outside the Arctic region too, affecting precipitation distribution over parts of the continental United States and Northeastern Pacific. For example, following sea ice recovery, wetter and milder winter conditions are present in the Southwest United States while the East Coast experiences cooling. We conclude that although ocean albedo alteration could lead to some sea ice recovery, it does not appear to be an effective way of offsetting the overall effects of CO₂ induced global warming.« less

Impacts of ocean albedo alteration on Arctic sea ice restoration and Northern Hemisphere climate

DOE PAGES

Cvijanovic, Ivana; Caldeira, Ken; MacMartin, Douglas G.

2015-04-01

The Arctic Ocean is expected to transition into a seasonally ice-free state by mid-century, enhancing Arctic warming and leading to substantial ecological and socio-economic challenges across the Arctic region. It has been proposed that artificially increasing high latitude ocean albedo could restore sea ice, but the climate impacts of such a strategy have not been previously explored. Motivated by this, we investigate the impacts of idealized high latitude ocean albedo changes on Arctic sea ice restoration and climate. In our simulated 4xCO₂ climate, imposing surface albedo alterations over the Arctic Ocean leads to partial sea ice recovery and a modestmore » reduction in Arctic warming. With the most extreme ocean albedo changes, imposed over the area 70°–90°N, September sea ice cover stabilizes at ~40% of its preindustrial value (compared to ~3% without imposed albedo modifications). This is accompanied by an annual mean Arctic surface temperature decrease of ~2 °C but no substantial global mean temperature decrease. Imposed albedo changes and sea ice recovery alter climate outside the Arctic region too, affecting precipitation distribution over parts of the continental United States and Northeastern Pacific. For example, following sea ice recovery, wetter and milder winter conditions are present in the Southwest United States while the East Coast experiences cooling. We conclude that although ocean albedo alteration could lead to some sea ice recovery, it does not appear to be an effective way of offsetting the overall effects of CO₂ induced global warming.« less

A New High Resolution Tidal Model in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Cancet, M.; Andersen, O.; Lyard, F.; Schulz, A.; Cotton, D.; Benveniste, J.

2016-08-01

The Arctic Ocean is a challenging region for tidal modelling. The accuracy of the global tidal models decreases by several centimeters in the Polar Regions, which has a large impact on the quality of the satellite altimeter sea surface heights and the altimetry-derived products.NOVELTIS and DTU Space have developed a regional, high-resolution tidal atlas in the Arctic Ocean, in the framework of an extension of the CryoSat Plus for Ocean (CP4O) ESA STSE (Support to Science Element) project. In particular, this atlas benefits from the assimilation of the most complete satellite altimetry dataset ever used in this region, including Envisat data up to 82°N and CryoSat-2 data between 82°N and 88°N. The combination of these satellite altimetry missions gives the best possible coverage of altimetry-derived tidal constituents. The available tide gauge data were also used for data assimilation and validation.This paper presents the implementation methodology and the performance of this new regional tidal model in the Arctic Ocean, compared to the existing global tidal models.

Late-Middle Quaternary lithostratigraphy and sedimentation patterns on the Alpha Ridge, central Arctic Ocean: Implications for Arctic climate variability on orbital time scales

NASA Astrophysics Data System (ADS)

Wang, Rujian; Polyak, Leonid; Xiao, Wenshen; Wu, Li; Zhang, Taoliang; Sun, Yechen; Xu, Xiaomei

2018-02-01

We use sediment cores collected by the Chinese National Arctic Research Expeditions from the Alpha Ridge to advance Quaternary stratigraphy and paleoceanographic reconstructions for the Arctic Ocean. Our cores show a good litho/biostratigraphic correlation to sedimentary records developed earlier for the central Arctic Ocean, suggesting a recovered stratigraphic range of ca. 0.6 Ma, suitable for paleoclimatic studies on orbital time scales. This stratigraphy was tested by correlating the stacked Alpha Ridge record of bulk XRF manganese, calcium and zirconium (Mn, Ca, Zr), to global stable-isotope (LR04-δ18O) and sea-level stacks and tuning to orbital parameters. Correlation results corroborate the applicability of presumed climate/sea-level controlled Mn variations in the Arctic Ocean for orbital tuning. This approach enables better understanding of the global and orbital controls on the Arctic climate. Orbital tuning experiments for our records indicate strong eccentricity (100-kyr) and precession (∼20-kyr) controls on the Arctic Ocean, probably implemented via glaciations and sea ice. Provenance proxies like Ca and Zr are shown to be unsuitable as orbital tuning tools, but useful as indicators of glacial/deglacial processes and circulation patterns in the Arctic Ocean. Their variations suggest an overall long-term persistence of the Beaufort Gyre circulation in the Alpha Ridge region. Some glacial intervals, e.g., MIS 6 and 4/3, are predominated by material presumably transported by the Transpolar Drift. These circulation shifts likely indicate major changes in the Arctic climatic regime, which yet need to be investigated. Overall, our results demonstrate applicability of XRF data to paleoclimatic studies of the Arctic Ocean.

Evidence for ice-ocean albedo feedback in the Arctic Ocean shifting to a seasonal ice zone.

PubMed

Kashiwase, Haruhiko; Ohshima, Kay I; Nihashi, Sohey; Eicken, Hajo

2017-08-15

Ice-albedo feedback due to the albedo contrast between water and ice is a major factor in seasonal sea ice retreat, and has received increasing attention with the Arctic Ocean shifting to a seasonal ice cover. However, quantitative evaluation of such feedbacks is still insufficient. Here we provide quantitative evidence that heat input through the open water fraction is the primary driver of seasonal and interannual variations in Arctic sea ice retreat. Analyses of satellite data (1979-2014) and a simplified ice-upper ocean coupled model reveal that divergent ice motion in the early melt season triggers large-scale feedback which subsequently amplifies summer sea ice anomalies. The magnitude of divergence controlling the feedback has doubled since 2000 due to a more mobile ice cover, which can partly explain the recent drastic ice reduction in the Arctic Ocean.

Evaluation of Arctic Sea Ice Thickness Simulated by Arctic Ocean Model Intercomparison Project Models

NASA Technical Reports Server (NTRS)

Johnson, Mark; Proshuntinsky, Andrew; Aksenov, Yevgeny; Nguyen, An T.; Lindsay, Ron; Haas, Christian; Zhang, Jinlun; Diansky, Nikolay; Kwok, Ron; Maslowski, Wieslaw;

A 4.5 km resolution Arctic Ocean simulation with the global multi-resolution model FESOM 1.4

NASA Astrophysics Data System (ADS)

Wang, Qiang; Wekerle, Claudia; Danilov, Sergey; Wang, Xuezhu; Jung, Thomas

2018-04-01

In the framework of developing a global modeling system which can facilitate modeling studies on Arctic Ocean and high- to midlatitude linkage, we evaluate the Arctic Ocean simulated by the multi-resolution Finite Element Sea ice-Ocean Model (FESOM). To explore the value of using high horizontal resolution for Arctic Ocean modeling, we use two global meshes differing in the horizontal resolution only in the Arctic Ocean (24 km vs. 4.5 km). The high resolution significantly improves the model's representation of the Arctic Ocean. The most pronounced improvement is in the Arctic intermediate layer, in terms of both Atlantic Water (AW) mean state and variability. The deepening and thickening bias of the AW layer, a common issue found in coarse-resolution simulations, is significantly alleviated by using higher resolution. The topographic steering of the AW is stronger and the seasonal and interannual temperature variability along the ocean bottom topography is enhanced in the high-resolution simulation. The high resolution also improves the ocean surface circulation, mainly through a better representation of the narrow straits in the Canadian Arctic Archipelago (CAA). The representation of CAA throughflow not only influences the release of water masses through the other gateways but also the circulation pathways inside the Arctic Ocean. However, the mean state and variability of Arctic freshwater content and the variability of freshwater transport through the Arctic gateways appear not to be very sensitive to the increase in resolution employed here. By highlighting the issues that are independent of model resolution, we address that other efforts including the improvement of parameterizations are still required.

Regional variations in provenance and abundance of ice-rafted clasts in Arctic Ocean sediments: Implications for the configuration of late Quaternary oceanic and atmospheric circulation in the Arctic

USGS Publications Warehouse

Phillips, R.L.; Grantz, A.

2001-01-01

The composition and distribution of ice-rafted glacial erratics in late Quaternary sediments define the major current systems of the Arctic Ocean and identify two distinct continental sources for the erratics. In the southern Amerasia basin up to 70% of the erratics are dolostones and limestones (the Amerasia suite) that originated in the carbonate-rich Paleozoic terranes of the Canadian Arctic Islands. These clasts reached the Arctic Ocean in glaciers and were ice-rafted to the core sites in the clockwise Beaufort Gyre. The concentration of erratics decreases northward by 98% along the trend of the gyre from southeastern Canada basin to Makarov basin. The concentration of erratics then triples across the Makarov basin flank of Lomonosov Ridge and siltstone, sandstone and siliceous clasts become dominant in cores from the ridge and the Eurasia basin (the Eurasia suite). The bedrock source for the siltstone and sandstone clasts is uncertain, but bedrock distribution and the distribution of glaciation in northern Eurasia suggest the Taymyr Peninsula-Kara Sea regions. The pattern of clast distribution in the Arctic Ocean sediments and the sharp northward decrease in concentration of clasts of Canadian Arctic Island provenance in the Amerasia basin support the conclusion that the modem circulation pattern of the Arctic Ocean, with the Beaufort Gyre dominant in the Amerasia basin and the Transpolar drift dominant in the Eurasia basin, has controlled both sea-ice and glacial iceberg drift in the Arctic Ocean during interglacial intervals since at least the late Pleistocene. The abruptness of the change in both clast composition and concentration on the Makarov basin flank of Lomonosov Ridge also suggests that the boundary between the Beaufort Gyre and the Transpolar Drift has been relatively stable during interglacials since that time. Because the Beaufort Gyre is wind-driven our data, in conjunction with the westerly directed orientation of sand dunes that formed during

Arctic-HYCOS: a Large Sample observing system for estimating freshwater fluxes in the drainage basin of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Pietroniro, Al; Korhonen, Johanna; Looser, Ulrich; Hardardóttir, Jórunn; Johnsrud, Morten; Vuglinsky, Valery; Gustafsson, David; Lins, Harry F.; Conaway, Jeffrey S.; Lammers, Richard; Stewart, Bruce; Abrate, Tommaso; Pilon, Paul; Sighomnou, Daniel; Arheimer, Berit

2015-04-01

The Arctic region is an important regulating component of the global climate system, and is also experiencing a considerable change during recent decades. More than 10% of world's river-runoff flows to the Arctic Ocean and there is evidence of changes in its fresh-water balance. However, about 30% of the Arctic basin is still ungauged, with differing monitoring practices and data availability from the countries in the region. A consistent system for monitoring and sharing of hydrological information throughout the Arctic region is thus of highest interest for further studies and monitoring of the freshwater flux to the Arctic Ocean. The purpose of the Arctic-HYCOS project is to allow for collection and sharing of hydrological data. Preliminary 616 stations were identified with long-term daily discharge data available, and around 250 of these already provide online available data in near real time. This large sample will be used in the following scientific analysis: 1) to evaluate freshwater flux to the Arctic Ocean and Seas, 2) to monitor changes and enhance understanding of the hydrological regime and 3) to estimate flows in ungauged regions and develop models for enhanced hydrological prediction in the Arctic region. The project is intended as a component of the WMO (World Meteorological Organization) WHYCOS (World Hydrological Cycle Observing System) initiative, covering the area of the expansive transnational Arctic basin with participation from Canada, Denmark, Finland, Iceland, Norway, Russian Federation, Sweden and United States of America. The overall objective is to regularly collect, manage and share high quality data from a defined basic network of hydrological stations in the Arctic basin. The project focus on collecting data on discharge and possibly sediment transport and temperature. Data should be provisional in near-real time if available, whereas time-series of historical data should be provided once quality assurance has been completed. The

The frequency and extent of sub-ice phytoplankton blooms in the Arctic Ocean

PubMed Central

Horvat, Christopher; Jones, David Rees; Iams, Sarah; Schroeder, David; Flocco, Daniela; Feltham, Daniel

2017-01-01

In July 2011, the observation of a massive phytoplankton bloom underneath a sea ice–covered region of the Chukchi Sea shifted the scientific consensus that regions of the Arctic Ocean covered by sea ice were inhospitable to photosynthetic life. Although the impact of widespread phytoplankton blooms under sea ice on Arctic Ocean ecology and carbon fixation is potentially marked, the prevalence of these events in the modern Arctic and in the recent past is, to date, unknown. We investigate the timing, frequency, and evolution of these events over the past 30 years. Although sea ice strongly attenuates solar radiation, it has thinned significantly over the past 30 years. The thinner summertime Arctic sea ice is increasingly covered in melt ponds, which permit more light penetration than bare or snow-covered ice. Our model results indicate that the recent thinning of Arctic sea ice is the main cause of a marked increase in the prevalence of light conditions conducive to sub-ice blooms. We find that as little as 20 years ago, the conditions required for sub-ice blooms may have been uncommon, but their frequency has increased to the point that nearly 30% of the ice-covered Arctic Ocean in July permits sub-ice blooms. Recent climate change may have markedly altered the ecology of the Arctic Ocean. PMID:28435859

Freshwater and its role in the Arctic Marine System: Sources, disposition, storage, export, and physical and biogeochemical consequences in the Arctic and global oceans

NASA Astrophysics Data System (ADS)

Carmack, E. C.; Yamamoto-Kawai, M.; Haine, T. W. N.; Bacon, S.; Bluhm, B. A.; Lique, C.; Melling, H.; Polyakov, I. V.; Straneo, F.; Timmermans, M.-L.; Williams, W. J.

2016-03-01

The Arctic Ocean is a fundamental node in the global hydrological cycle and the ocean's thermohaline circulation. We here assess the system's key functions and processes: (1) the delivery of fresh and low-salinity waters to the Arctic Ocean by river inflow, net precipitation, distillation during the freeze/thaw cycle, and Pacific Ocean inflows; (2) the disposition (e.g., sources, pathways, and storage) of freshwater components within the Arctic Ocean; and (3) the release and export of freshwater components into the bordering convective domains of the North Atlantic. We then examine physical, chemical, or biological processes which are influenced or constrained by the local quantities and geochemical qualities of freshwater; these include stratification and vertical mixing, ocean heat flux, nutrient supply, primary production, ocean acidification, and biogeochemical cycling. Internal to the Arctic the joint effects of sea ice decline and hydrological cycle intensification have strengthened coupling between the ocean and the atmosphere (e.g., wind and ice drift stresses, solar radiation, and heat and moisture exchange), the bordering drainage basins (e.g., river discharge, sediment transport, and erosion), and terrestrial ecosystems (e.g., Arctic greening, dissolved and particulate carbon loading, and altered phenology of biotic components). External to the Arctic freshwater export acts as both a constraint to and a necessary ingredient for deep convection in the bordering subarctic gyres and thus affects the global thermohaline circulation. Geochemical fingerprints attained within the Arctic Ocean are likewise exported into the neighboring subarctic systems and beyond. Finally, we discuss observed and modeled functions and changes in this system on seasonal, annual, and decadal time scales and discuss mechanisms that link the marine system to atmospheric, terrestrial, and cryospheric systems.

Amino acid epimerization implies rapid sedimentation rates in Arctic Ocean cores

USGS Publications Warehouse

Sejrup, H.P.; Miller, G.H.; Brigham-Grette, J.; Lovlie, R.; Hopkins, D.

1984-01-01

The palaeooceanography of the Arctic Ocean is less well known than any other ocean basin, due to difficulties in obtaining cores and in providing a secure chronological framework for those cores that have been raised. Most recent investigators have suggested that low sedimentation rates (0.05-0.1 cm kyr-1) have characterized the deep basins over the past 5 Myr (refs 1,2) despite the glacial-marine character of the sediment and proximity to major centres of shelf glaciation. These calculations have been primarily based on the down-core pattern in the inclination of magnetic minerals, supported by uranium-series, 14C and micropalaeontological evidence. Here we analyse amino acid diagnesis in foraminifera from two gravity cores raised from the floor of the Arctic Ocean, our results suggest that these cores span <200 kyr., conflicting with the earlier estimate of 3 Myr based on palaeomagnetic data. The chronology of other Arctic Ocean cores and previous palaeoenvironmental interpretations need re-evaluation. ?? 1984 Nature Publishing Group.

Nudging the Arctic Ocean to quantify Arctic sea ice feedbacks

NASA Astrophysics Data System (ADS)

Dekker, Evelien; Severijns, Camiel; Bintanja, Richard

2017-04-01

It is well-established that the Arctic is warming 2 to 3 time faster than rest of the planet. One of the great uncertainties in climate research is related to what extent sea ice feedbacks amplify this (seasonally varying) Arctic warming. Earlier studies have analyzed existing climate model output using correlations and energy budget considerations in order to quantify sea ice feedbacks through indirect methods. From these analyses it is regularly inferred that sea ice likely plays an important role, but details remain obscure. Here we will take a different and a more direct approach: we will keep the sea ice constant in a sensitivity simulation, using a state-of -the-art climate model (EC-Earth), applying a technique that has never been attempted before. This experimental technique involves nudging the temperature and salinity of the ocean surface (and possibly some layers below to maintain the vertical structure and mixing) to a predefined prescribed state. When strongly nudged to existing (seasonally-varying) sea surface temperatures, ocean salinity and temperature, we force the sea ice to remain in regions/seasons where it is located in the prescribed state, despite the changing climate. Once we obtain fixed' sea ice, we will run a future scenario, for instance 2 x CO2 with and without prescribed sea ice, with the difference between these runs providing a measure as to what extent sea ice contributes to Arctic warming, including the seasonal and geographical imprint of the effects.

The Cenozoic palaeoenvironment of the Arctic Ocean

USGS Publications Warehouse

Moran, K.; Backman, J.; Brinkhuis, H.; Clemens, S.C.; Cronin, T.; Dickens, G.R.; Eynaud, F.; Gattacceca, J.; Jakobsson, M.; Jordan, R.W.; Kaminski, M.; King, J.; Koc, N.; Krylov, A.; Martinez, N.; Matthiessen, J.; McInroy, D.; Moore, T.C.; Onodera, J.; O'Regan, M.; Palike, H.; Rea, B.; Rio, D.; Sakamoto, T.; Smith, D.C.; Stein, R.; St, John K.; Suto, I.; Suzuki, N.; Takahashi, K.; Watanabe, M. E.; Yamamoto, M.; Farrell, J.; Frank, M.; Kubik, P.; Jokat, W.; Kristoffersen, Y.

2006-01-01

The history of the Arctic Ocean during the Cenozoic era (0-65 million years ago) is largely unknown from direct evidence. Here we present a Cenozoic palaeoceanographic record constructed from >400 m of sediment core from a recent drilling expedition to the Lomonosov ridge in the Arctic Ocean. Our record shows a palaeoenvironmental transition from a warm 'greenhouse' world, during the late Palaeocene and early Eocene epochs, to a colder 'icehouse' world influenced by sea ice and icebergs from the middle Eocene epoch to the present. For the most recent ???14 Myr, we find sedimentation rates of 1-2 cm per thousand years, in stark contrast to the substantially lower rates proposed in earlier studies; this record of the Neogene reveals cooling of the Arctic that was synchronous with the expansion of Greenland ice (???3.2 Myr ago) and East Antarctic ice (???14 Myr ago). We find evidence for the first occurrence of ice-rafted debris in the middle Eocene epoch (???45 Myr ago), some 35 Myr earlier than previously thought; fresh surface waters were present at ???49 Myr ago, before the onset of ice-rafted debris. Also, the temperatures of surface waters during the Palaeocene/Eocene thermal maximum (???55 Myr ago) appear to have been substantially warmer than previously estimated. The revised timing of the earliest Arctic cooling events coincides with those from Antarctica, supporting arguments for bipolar symmetry in climate change. ?? 2006 Nature Publishing Group.

High colored dissolved organic matter (CDOM) absorption in surface waters of the central-eastern Arctic Ocean: Implications for biogeochemistry and ocean color algorithms

PubMed Central

Rabe, Benjamin; Peeken, Ilka; Bracher, Astrid

2018-01-01

As consequences of global warming sea-ice shrinking, permafrost thawing and changes in fresh water and terrestrial material export have already been reported in the Arctic environment. These processes impact light penetration and primary production. To reach a better understanding of the current status and to provide accurate forecasts Arctic biogeochemical and physical parameters need to be extensively monitored. In this sense, bio-optical properties are useful to be measured due to the applicability of optical instrumentation to autonomous platforms, including satellites. This study characterizes the non-water absorbers and their coupling to hydrographic conditions in the poorly sampled surface waters of the central and eastern Arctic Ocean. Over the entire sampled area colored dissolved organic matter (CDOM) dominates the light absorption in surface waters. The distribution of CDOM, phytoplankton and non-algal particles absorption reproduces the hydrographic variability in this region of the Arctic Ocean which suggests a subdivision into five major bio-optical provinces: Laptev Sea Shelf, Laptev Sea, Central Arctic/Transpolar Drift, Beaufort Gyre and Eurasian/Nansen Basin. Evaluating ocean color algorithms commonly applied in the Arctic Ocean shows that global and regionally tuned empirical algorithms provide poor chlorophyll-a (Chl-a) estimates. The semi-analytical algorithms Generalized Inherent Optical Property model (GIOP) and Garver-Siegel-Maritorena (GSM), on the other hand, provide robust estimates of Chl-a and absorption of colored matter. Applying GSM with modifications proposed for the western Arctic Ocean produced reliable information on the absorption by colored matter, and specifically by CDOM. These findings highlight that only semi-analytical ocean color algorithms are able to identify with low uncertainty the distribution of the different optical water constituents in these high CDOM absorbing waters. In addition, a clustering of the Arctic Ocean

High colored dissolved organic matter (CDOM) absorption in surface waters of the central-eastern Arctic Ocean: Implications for biogeochemistry and ocean color algorithms.

PubMed

Gonçalves-Araujo, Rafael; Rabe, Benjamin; Peeken, Ilka; Bracher, Astrid

2018-01-01

As consequences of global warming sea-ice shrinking, permafrost thawing and changes in fresh water and terrestrial material export have already been reported in the Arctic environment. These processes impact light penetration and primary production. To reach a better understanding of the current status and to provide accurate forecasts Arctic biogeochemical and physical parameters need to be extensively monitored. In this sense, bio-optical properties are useful to be measured due to the applicability of optical instrumentation to autonomous platforms, including satellites. This study characterizes the non-water absorbers and their coupling to hydrographic conditions in the poorly sampled surface waters of the central and eastern Arctic Ocean. Over the entire sampled area colored dissolved organic matter (CDOM) dominates the light absorption in surface waters. The distribution of CDOM, phytoplankton and non-algal particles absorption reproduces the hydrographic variability in this region of the Arctic Ocean which suggests a subdivision into five major bio-optical provinces: Laptev Sea Shelf, Laptev Sea, Central Arctic/Transpolar Drift, Beaufort Gyre and Eurasian/Nansen Basin. Evaluating ocean color algorithms commonly applied in the Arctic Ocean shows that global and regionally tuned empirical algorithms provide poor chlorophyll-a (Chl-a) estimates. The semi-analytical algorithms Generalized Inherent Optical Property model (GIOP) and Garver-Siegel-Maritorena (GSM), on the other hand, provide robust estimates of Chl-a and absorption of colored matter. Applying GSM with modifications proposed for the western Arctic Ocean produced reliable information on the absorption by colored matter, and specifically by CDOM. These findings highlight that only semi-analytical ocean color algorithms are able to identify with low uncertainty the distribution of the different optical water constituents in these high CDOM absorbing waters. In addition, a clustering of the Arctic Ocean

Compensation of ocean acidification effects in Arctic phytoplankton assemblages

NASA Astrophysics Data System (ADS)

Hoppe, Clara Jule Marie; Wolf, Klara K. E.; Schuback, Nina; Tortell, Philippe D.; Rost, Björn

2018-06-01

The Arctic and subarctic shelf seas, which sustain large fisheries and contribute to global biogeochemical cycling, are particularly sensitive to ongoing ocean acidification (that is, decreasing seawater pH due to anthropogenic CO2 emissions). Yet, little information is available on the effects of ocean acidification on natural phytoplankton assemblages, which are the main primary producers in high-latitude waters. Here we show that coastal Arctic and subarctic primary production is largely insensitive to ocean acidification over a large range of light and temperature levels in different experimental designs. Out of ten CO2-manipulation treatments, significant ocean acidification effects on primary productivity were observed only once (at temperatures below 2 °C), and shifts in the species composition occurred only three times (without correlation to specific experimental conditions). These results imply a high capacity to compensate for environmental variability, which can be understood in light of the environmental history, tolerance ranges and intraspecific diversity of the dominant phytoplankton species.

Biological response to climate change in the Arctic Ocean: The view from the past

USGS Publications Warehouse

Cronin, Thomas M.; Cronin, Matthew A.

2017-01-01

The Arctic Ocean is undergoing rapid climatic changes including higher ocean temperatures, reduced sea ice, glacier and Greenland Ice Sheet melting, greater marine productivity, and altered carbon cycling. Until recently, the relationship between climate and Arctic biological systems was poorly known, but this has changed substantially as advances in paleoclimatology, micropaleontology, vertebrate paleontology, and molecular genetics show that Arctic ecosystem history reflects global and regional climatic changes over all timescales and climate states (103–107 years). Arctic climatic extremes include 25°C hyperthermal periods during the Paleocene-Eocene (56–46 million years ago, Ma), Quaternary glacial periods when thick ice shelves and sea ice cover rendered the Arctic Ocean nearly uninhabitable, seasonally sea-ice-free interglacials and abrupt climate reversals. Climate-driven biological impacts included large changes in species diversity, primary productivity, species’ geographic range shifts into and out of the Arctic, community restructuring, and possible hybridization, but evidence is not sufficient to determine whether or when major episodes of extinction occurred.

Arctic Ocean Model Intercomparison Using Sound Speed

NASA Astrophysics Data System (ADS)

Dukhovskoy, D. S.; Johnson, M. A.

2002-05-01

The monthly and annual means from three Arctic ocean - sea ice climate model simulations are compared for the period 1979-1997. Sound speed is used to integrate model outputs of temperature and salinity along a section between Barrow and Franz Josef Land. A statistical approach is used to test for differences among the three models for two basic data subsets. We integrated and then analyzed an upper layer between 2 m - 50 m, and also a deep layer from 500 m to the bottom. The deep layer is characterized by low time-variability. No high-frequency signals appear in the deep layer having been filtered out in the upper layer. There is no seasonal signal in the deep layer and the monthly means insignificantly oscillate about the long-period mean. For the deep ocean the long-period mean can be considered quasi-constant, at least within the 19 year period of our analysis. Thus we assumed that the deep ocean would be the best choice for comparing the means of the model outputs. The upper (mixed) layer was chosen to contrast the deep layer dynamics. There are distinct seasonal and interannual signals in the sound speed time series in this layer. The mixed layer is a major link in the ocean - air interaction mechanism. Thus, different mean states of the upper layer in the models might cause different responses in other components of the Arctic climate system. The upper layer also strongly reflects any differences in atmosphere forcing. To compare data from the three models we have used a one-way t-test for the population mean, the Wilcoxon one-sample signed-rank test (when the requirement of normality of tested data is violated), and one-way ANOVA method and F-test to verify our hypothesis that the model outputs have the same mean sound speed. The different statistical approaches have shown that all models have different mean characteristics of the deep and upper layers of the Arctic Ocean.

An updated 26-year (1991-2017) sea level record from the Arctic Ocean

NASA Astrophysics Data System (ADS)

Kildegaard Rose, Stine; Baltazar Andersen, Ole; Passaro, Marcello; Benveniste, Jerome

2017-04-01

In recent years, there has been a large focus of the Arctic due the rapid changes of the region. The sea level of the Arctic Ocean is an important climate indicator. The Arctic sea ice is decreasing and has since 1997 experienced a steepening in the decrease. The Arctic sea level determination is challenging due to the seasonal to permanent sea ice cover, the lack of regional coverage of satellites, the satellite instruments ability to measure ice, insufficient geophysical models, residual orbit errors, challenging retracking of satellite altimeter data. We present the DTU/TUM 26-year sea level record based on satellite altimetry data in the Arctic Ocean from the ERS1 (1991) to CryoSat-2 (present) satellites. The sea level record is compared with several tide gauges and other available partial sea level records contributing to the ESA CCI Sea level initiative. We use updated geophysical corrections and a combination of altimeter data: REAPER (ERS1), ALES+ retracker (ERS2, Envisat), combined Rads and DTUs in-house retracker LARS (CryoSat-2). The ALES+ is an upgraded version of the Adaptive Leading Edge Subwaveform Retracker that has been developed to improve data quality and quantity in the coastal ocean, without degrading the results in the open ocean. ALES+ aims at retracking peaky waveforms typical of lead reflections without modifying the fitting model used in the open ocean.

Future change in ocean productivity: Is the Arctic the new Atlantic?

NASA Astrophysics Data System (ADS)

Yool, A.; Popova, E. E.; Coward, A. C.

2015-12-01

One of the most characteristic features in ocean productivity is the North Atlantic spring bloom. Responding to seasonal increases in irradiance and stratification, surface phytopopulations rise significantly, a pattern that visibly tracks poleward into summer. While blooms also occur in the Arctic Ocean, they are constrained by the sea-ice and strong vertical stratification that characterize this region. However, Arctic sea-ice is currently declining, and forecasts suggest this may lead to completely ice-free summers by the mid-21st century. Such change may open the Arctic up to Atlantic-style spring blooms, and do so at the same time as Atlantic productivity is threatened by climate change-driven ocean stratification. Here we use low and high-resolution instances of a coupled ocean-biogeochemistry model, NEMO-MEDUSA, to investigate productivity. Drivers of present-day patterns are identified, and changes in these across a climate change scenario (IPCC RCP 8.5) are analyzed. We find a globally significant decline in North Atlantic productivity (> -20%) by 2100, and a correspondingly significant rise in the Arctic (> +50%). However, rather than the future Arctic coming to resemble the current Atlantic, both regions are instead transitioning to a common, low nutrient regime. The North Pacific provides a counterexample where nutrients remain high and productivity increases with elevated temperature. These responses to climate change in the Atlantic and Arctic are common between model resolutions, suggesting an independence from resolution for key impacts. However, some responses, such as those in the North Pacific, differ between the simulations, suggesting the reverse and supporting the drive to more fine-scale resolutions. This article was corrected on 5 JAN 2016. See the end of the full text for details.

Occurrence of perfluoroalkyl compounds in surface waters from the North Pacific to the Arctic Ocean.

PubMed

Cai, Minghong; Zhao, Zhen; Yin, Zhigao; Ahrens, Lutz; Huang, Peng; Cai, Minggang; Yang, Haizhen; He, Jianfeng; Sturm, Renate; Ebinghaus, Ralf; Xie, Zhiyong

2012-01-17

Perfluoroalkyl compounds (PFCs) were determined in 22 surface water samples (39-76°N) and three sea ice core and snow samples (77-87°N) collected from North Pacific to the Arctic Ocean during the fourth Chinese Arctic Expedition in 2010. Geographically, the average concentration of ∑PFC in surface water samples were 560 ± 170 pg L(-1) for the Northwest Pacific Ocean, 500 ± 170 pg L(-1) for the Arctic Ocean, and 340 ± 130 pg L(-1) for the Bering Sea, respectively. The perfluoroalkyl carboxylates (PFCAs) were the dominant PFC class in the water samples, however, the spatial pattern of PFCs varied. The C(5), C(7) and C(8) PFCAs (i.e., perfluoropentanoate (PFPA), perfluoroheptanoate (PFHpA), and perfluorooctanoate (PFOA)) were the dominant PFCs in the Northwest Pacific Ocean while in the Bering Sea the PFPA dominated. The changing in the pattern and concentrations in Pacific Ocean indicate that the PFCs in surface water were influenced by sources from the East-Asian (such as Japan and China) and North American coast, and dilution effect during their transport to the Arctic. The presence of PFCs in the snow and ice core samples indicates an atmospheric deposition of PFCs in the Arctic. The elevated PFC concentration in the Arctic Ocean shows that the ice melting had an impact on the PFC levels and distribution. In addition, the C(4) and C(5) PFCAs (i.e., perfluorobutanoate (PFBA), PFPA) became the dominant PFCs in the Arctic Ocean indicating that PFBA is a marker for sea ice melting as the source of exposure.

The Arctic Summer Cloud-Ocean Study (ASCOS): overview and experimental design

NASA Astrophysics Data System (ADS)

Tjernström, M.; Leck, C.; Birch, C. E.; Brooks, B. J.; Brooks, I. M.; Bäcklin, L.; Chang, R. Y.-W.; Granath, E.; Graus, M.; Hansel, A.; Heintzenberg, J.; Held, A.; Hind, A.; de la Rosa, S.; Johnston, P.; Knulst, J.; de Leeuw, G.; Di Liberto, L.; Martin, M.; Matrai, P. A.; Mauritsen, T.; Müller, M.; Norris, S. J.; Orellana, M. V.; Orsini, D. A.; Paatero, J.; Persson, P. O. G.; Gao, Q.; Rauschenberg, C.; Ristovski, Z.; Sedlar, J.; Shupe, M. D.; Sierau, B.; Sirevaag, A.; Sjogren, S.; Stetzer, O.; Swietlicki, E.; Szczodrak, M.; Vaattovaara, P.; Wahlberg, N.; Westberg, M.; Wheeler, C. R.

2013-05-01

The climate in the Arctic is changing faster than anywhere else on Earth. Poorly understood feedback processes relating to Arctic clouds and aerosol-cloud interactions contribute to a poor understanding of the present changes in the Arctic climate system, and also to a large spread in projections of future climate in the Arctic. The problem is exacerbated by the paucity of research-quality observations in the central Arctic. Improved formulations in climate models require such observations, which can only come from measurements in-situ in this difficult to reach region with logistically demanding environmental conditions. The Arctic Summer Cloud-Ocean Study (ASCOS) was the most extensive central Arctic Ocean expedition with an atmospheric focus during the International Polar Year (IPY) 2007-2008. ASCOS focused on the study of the formation and life cycle of low-level Arctic clouds. ASCOS departed from Longyearbyen on Svalbard on 2 August and returned on 9 September 2008. In transit into and out of the pack ice, four short research stations were undertaken in the Fram Strait; two in open water and two in the marginal ice zone. After traversing the pack-ice northward an ice camp was set up on 12 August at 87°21' N 01°29' W and remained in operation through 1 September, drifting with the ice. During this time extensive measurements were taken of atmospheric gas and particle chemistry and physics, mesoscale and boundary-layer meteorology, marine biology and chemistry, and upper ocean physics. ASCOS provides a unique interdisciplinary data set for development and testing of new hypotheses on cloud processes, their interactions with the sea ice and ocean and associated physical, chemical, and biological processes and interactions. For example, the first ever quantitative observation of bubbles in Arctic leads, combined with the unique discovery of marine organic material, polymer gels with an origin in the ocean, inside cloud droplets suggest the possibility of primary

The Arctic Summer Cloud Ocean Study (ASCOS): overview and experimental design

NASA Astrophysics Data System (ADS)

Tjernström, M.; Leck, C.; Birch, C. E.; Bottenheim, J. W.; Brooks, B. J.; Brooks, I. M.; Bäcklin, L.; Chang, R. Y.-W.; de Leeuw, G.; Di Liberto, L.; de la Rosa, S.; Granath, E.; Graus, M.; Hansel, A.; Heintzenberg, J.; Held, A.; Hind, A.; Johnston, P.; Knulst, J.; Martin, M.; Matrai, P. A.; Mauritsen, T.; Müller, M.; Norris, S. J.; Orellana, M. V.; Orsini, D. A.; Paatero, J.; Persson, P. O. G.; Gao, Q.; Rauschenberg, C.; Ristovski, Z.; Sedlar, J.; Shupe, M. D.; Sierau, B.; Sirevaag, A.; Sjogren, S.; Stetzer, O.; Swietlicki, E.; Szczodrak, M.; Vaattovaara, P.; Wahlberg, N.; Westberg, M.; Wheeler, C. R.

2014-03-01

The climate in the Arctic is changing faster than anywhere else on earth. Poorly understood feedback processes relating to Arctic clouds and aerosol-cloud interactions contribute to a poor understanding of the present changes in the Arctic climate system, and also to a large spread in projections of future climate in the Arctic. The problem is exacerbated by the paucity of research-quality observations in the central Arctic. Improved formulations in climate models require such observations, which can only come from measurements in situ in this difficult-to-reach region with logistically demanding environmental conditions. The Arctic Summer Cloud Ocean Study (ASCOS) was the most extensive central Arctic Ocean expedition with an atmospheric focus during the International Polar Year (IPY) 2007-2008. ASCOS focused on the study of the formation and life cycle of low-level Arctic clouds. ASCOS departed from Longyearbyen on Svalbard on 2 August and returned on 9 September 2008. In transit into and out of the pack ice, four short research stations were undertaken in the Fram Strait: two in open water and two in the marginal ice zone. After traversing the pack ice northward, an ice camp was set up on 12 August at 87°21' N, 01°29' W and remained in operation through 1 September, drifting with the ice. During this time, extensive measurements were taken of atmospheric gas and particle chemistry and physics, mesoscale and boundary-layer meteorology, marine biology and chemistry, and upper ocean physics. ASCOS provides a unique interdisciplinary data set for development and testing of new hypotheses on cloud processes, their interactions with the sea ice and ocean and associated physical, chemical, and biological processes and interactions. For example, the first-ever quantitative observation of bubbles in Arctic leads, combined with the unique discovery of marine organic material, polymer gels with an origin in the ocean, inside cloud droplets suggests the possibility of

Arctic Ocean Freshwater Content and Its Decadal Memory of Sea-Level Pressure

NASA Astrophysics Data System (ADS)

Johnson, Helen L.; Cornish, Sam B.; Kostov, Yavor; Beer, Emma; Lique, Camille

2018-05-01

Arctic freshwater content (FWC) has increased significantly over the last two decades, with potential future implications for the Atlantic meridional overturning circulation downstream. We investigate the relationship between Arctic FWC and atmospheric circulation in the control run of a coupled climate model. Multiple linear lagged regression is used to extract the response of total Arctic FWC to a hypothetical step increase in the principal components of sea-level pressure. The results demonstrate that the FWC adjusts on a decadal timescale, consistent with the idea that wind-driven ocean dynamics and eddies determine the response of Arctic Ocean circulation and properties to a change in surface forcing, as suggested by idealized models and theory. Convolving the response of FWC to a change in sea-level pressure with historical sea-level pressure variations reveals that the recent observed increase in Arctic FWC is related to natural variations in sea-level pressure.

A distributed atmosphere-sea ice-ocean observatory in the central Arctic Ocean: concept and first results

NASA Astrophysics Data System (ADS)

Hoppmann, Mario; Nicolaus, Marcel; Rabe, Benjamin; Wenzhöfer, Frank; Katlein, Christian; Scholz, Daniel; Valcic, Lovro

2017-04-01

To understand the current evolution of the Arctic Ocean towards a less extensive, thinner and younger sea ice cover is one of the biggest challenges in climate research. Especially the lack of simultaneous in-situ observations of sea ice, ocean and atmospheric properties leads to significant knowledge gaps in their complex interactions, and how the associated processes impact the polar marine ecosystem. Here we present a concept for the implementation of a long-term strategy to monitor the most essential climate- and ecosystem parameters in the central Arctic Ocean, year round and synchronously. The basis of this strategy is the development and enhancement of a number of innovative autonomous observational platforms, such as rugged weather stations, ice mass balance buoys, ice-tethered bio-optical buoys and upper ocean profilers. The deployment of those complementing platforms in a distributed network enables the simultaneous collection of physical and biogeochemical in-situ data on basin scales and year round, including the largely undersampled winter periods. A key advantage over other observatory systems is that the data is sent via satellite in near-real time, contributing to numerical weather predictions through the Global Telecommunication System (GTS) and to the International Arctic Buoy Programme (IABP). The first instruments were installed on ice floes in the Eurasian Basin in spring 2015 and 2016, yielding exceptional records of essential climate- and ecosystem-relevant parameters in one of the most inaccessible regions of this planet. Over the next 4 years, and including the observational periods of the Year of Polar Prediction (YOPP, 2017-2019) and the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC, 2020), the distributed observatory will be maintained by deployment of additional instruments in the central Arctic each year, benefitting from international logistical efforts.

Evidence for an ice shelf covering the central Arctic Ocean during the penultimate glaciation

USGS Publications Warehouse

Jakobsson, Martin; Nilsson, Johan; Anderson, Leif G.; Backman, Jan; Bjork, Goran; Cronin, Thomas M.; Kirchner, Nina; Koshurnikov, Andrey; Mayer, Larry; Noormets, Riko; O'Regan, Matthew; Stranne, Christian; Ananiev, Roman; Macho, Natalia Barrientos; Cherniykh, Dennis; Coxall, Helen; Eriksson, Bjorn; Floden, Tom; Gemery, Laura; Gustafsson, Orjan; Jerram, Kevin; Johansson, Carina; Khortov, Alexey; Mohammad, Rezwan; Semiletov, Igor

2016-01-01

The hypothesis of a km-thick ice shelf covering the entire Arctic Ocean during peak glacial conditions was proposed nearly half a century ago. Floating ice shelves preserve few direct traces after their disappearance, making reconstructions difficult. Seafloor imprints of ice shelves should, however, exist where ice grounded along their flow paths. Here we present new evidence of ice-shelf groundings on bathymetric highs in the central Arctic Ocean, resurrecting the concept of an ice shelf extending over the entire central Arctic Ocean during at least one previous ice age. New and previously mapped glacial landforms together reveal flow of a spatially coherent, in some regions >1-km thick, central Arctic Ocean ice shelf dated to marine isotope stage 6 (~140 ka). Bathymetric highs were likely critical in the ice-shelf development by acting as pinning points where stabilizing ice rises formed, thereby providing sufficient back stress to allow ice shelf thickening.

Evidence for an ice shelf covering the central Arctic Ocean during the penultimate glaciation

PubMed Central

Jakobsson, Martin; Nilsson, Johan; Anderson, Leif; Backman, Jan; Björk, Göran; Cronin, Thomas M.; Kirchner, Nina; Koshurnikov, Andrey; Mayer, Larry; Noormets, Riko; O'Regan, Matthew; Stranne, Christian; Ananiev, Roman; Barrientos Macho, Natalia; Cherniykh, Denis; Coxall, Helen; Eriksson, Björn; Flodén, Tom; Gemery, Laura; Gustafsson, Örjan; Jerram, Kevin; Johansson, Carina; Khortov, Alexey; Mohammad, Rezwan; Semiletov, Igor

2016-01-01

The hypothesis of a km-thick ice shelf covering the entire Arctic Ocean during peak glacial conditions was proposed nearly half a century ago. Floating ice shelves preserve few direct traces after their disappearance, making reconstructions difficult. Seafloor imprints of ice shelves should, however, exist where ice grounded along their flow paths. Here we present new evidence of ice-shelf groundings on bathymetric highs in the central Arctic Ocean, resurrecting the concept of an ice shelf extending over the entire central Arctic Ocean during at least one previous ice age. New and previously mapped glacial landforms together reveal flow of a spatially coherent, in some regions >1-km thick, central Arctic Ocean ice shelf dated to marine isotope stage 6 (∼140 ka). Bathymetric highs were likely critical in the ice-shelf development by acting as pinning points where stabilizing ice rises formed, thereby providing sufficient back stress to allow ice shelf thickening. PMID:26778247

Polycyclic aromatic hydrocarbons in ocean sediments from the North Pacific to the Arctic Ocean.

PubMed

Ma, Yuxin; Halsall, Crispin J; Xie, Zhiyong; Koetke, Danijela; Mi, Wenying; Ebinghaus, Ralf; Gao, Guoping

2017-08-01

Eighteen polycyclic aromatic hydrocarbons (PAHs) were measured in surficial sediments along a marine transect from the North Pacific into the Arctic Ocean. The highest average Σ 18 PAHs concentrations were observed along the continental slope of the Canada Basin in the Arctic (68.3 ± 8.5 ng g -1 dw), followed by sediments in the Chukchi Sea shelf (49.7 ± 21.2 ng g -1 dw) and Bering Sea (39.5 ± 11.3 ng g -1 dw), while the Bering Strait (16.8 ± 7.1 ng g -1 dw) and Central Arctic Ocean sediments (13.1 ± 9.6 ng g -1 dw) had relatively lower average concentrations. The use of principal components analysis with multiple linear regression (PCA/MLR) indicated that on average oil related or petrogenic sources contributed ∼42% of the measured PAHs in the sediments and marked by higher concentrations of two methylnaphthalenes over the non-alkylated parent PAH, naphthalene. Wood and coal combustion contributed ∼32%, and high temperature pyrogenic sources contributing ∼26%. Petrogenic sources, such as oil seeps, allochthonous coal and coastally eroded material such as terrigenous sediments particularly affected the Chukchi Sea shelf and slope of the Canada Basin, while biomass and coal combustion sources appeared to have greater influence in the central Arctic Ocean, possibly due to the effects of episodic summertime forest fires. Copyright © 2017 Elsevier Ltd. All rights reserved.

Atmospheric moisture transport: the bridge between ocean evaporation and Arctic ice melting

NASA Astrophysics Data System (ADS)

Gimeno, L.; Vázquez, M.; Nieto, R.; Trigo, R. M.

2015-09-01

Changes in the atmospheric moisture transport have been proposed as a vehicle for interpreting some of the most significant changes in the Arctic region. The increasing moisture over the Arctic during the last decades is not strongly associated with the evaporation that takes place within the Arctic area itself, despite the fact that the sea ice cover is decreasing. Such an increment is consistent and is more dependent on the transport of moisture from the extratropical regions to the Arctic that has increased in recent decades and is expected to increase within a warming climate. This increase could be due either to changes in circulation patterns which have altered the moisture sources, or to changes in the intensity of the moisture sources because of enhanced evaporation, or a combination of these two mechanisms. In this short communication we focus on the more objective assessment of the strong link between ocean evaporation trends and Arctic Sea ice melting. We will critically analyse several recent results suggesting links between moisture transport and the extent of sea ice in the Arctic, this being one of the most distinct indicators of continuous climate change both in the Arctic and on a global scale. To do this we will use a sophisticated Lagrangian approach to develop a more robust framework on some of these previous disconnecting results, using new information and insights. Results reached in this study stress the connection between two climate change indicators, namely an increase in evaporation over source regions (mainly the Mediterranean Sea, the North Atlantic Ocean and the North Pacific Ocean in the paths of the global western boundary currents and their extensions) and Arctic ice melting precursors.

Cloud-Scale Numerical Modeling of the Arctic Boundary Layer

NASA Technical Reports Server (NTRS)

Krueger, Steven K.

1998-01-01

The interactions between sea ice, open ocean, atmospheric radiation, and clouds over the Arctic Ocean exert a strong influence on global climate. Uncertainties in the formulation of interactive air-sea-ice processes in global climate models (GCMs) result in large differences between the Arctic, and global, climates simulated by different models. Arctic stratus clouds are not well-simulated by GCMs, yet exert a strong influence on the surface energy budget of the Arctic. Leads (channels of open water in sea ice) have significant impacts on the large-scale budgets during the Arctic winter, when they contribute about 50 percent of the surface fluxes over the Arctic Ocean, but cover only 1 to 2 percent of its area. Convective plumes generated by wide leads may penetrate the surface inversion and produce condensate that spreads up to 250 km downwind of the lead, and may significantly affect the longwave radiative fluxes at the surface and thereby the sea ice thickness. The effects of leads and boundary layer clouds must be accurately represented in climate models to allow possible feedbacks between them and the sea ice thickness. The FIRE III Arctic boundary layer clouds field program, in conjunction with the SHEBA ice camp and the ARM North Slope of Alaska and Adjacent Arctic Ocean site, will offer an unprecedented opportunity to greatly improve our ability to parameterize the important effects of leads and boundary layer clouds in GCMs.

Early ice retreat and ocean warming may induce copepod biogeographic boundary shifts in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Feng, Zhixuan; Ji, Rubao; Campbell, Robert G.; Ashjian, Carin J.; Zhang, Jinlun

2016-08-01

Early ice retreat and ocean warming are changing various facets of the Arctic marine ecosystem, including the biogeographic distribution of marine organisms. Here an endemic copepod species, Calanus glacialis, was used as a model organism, to understand how and why Arctic marine environmental changes may induce biogeographic boundary shifts. A copepod individual-based model was coupled to an ice-ocean-ecosystem model to simulate temperature- and food-dependent copepod life history development. Numerical experiments were conducted for two contrasting years: a relatively cold and normal sea ice year (2001) and a well-known warm year with early ice retreat (2007). Model results agreed with commonly known biogeographic distributions of C. glacialis, which is a shelf/slope species and cannot colonize the vast majority of the central Arctic basins. Individuals along the northern boundaries of this species' distribution were most susceptible to reproduction timing and early food availability (released sea ice algae). In the Beaufort, Chukchi, East Siberian, and Laptev Seas where severe ocean warming and loss of sea ice occurred in summer 2007, relatively early ice retreat, elevated ocean temperature (about 1-2°C higher than 2001), increased phytoplankton food, and prolonged growth season created favorable conditions for C. glacialis development and caused a remarkable poleward expansion of its distribution. From a pan-Arctic perspective, despite the great heterogeneity in the temperature and food regimes, common biogeographic zones were identified from model simulations, thus allowing a better characterization of habitats and prediction of potential future biogeographic boundary shifts.

Altimeter Observations of Wave Climate in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Babanin, A. V.; Liu, Q.; Zieger, S.

2016-02-01

Wind waves are a new physical phenomenon to the Arctic Seas, which in the past were covered with ice. Now, over summer months, ice coverage retreats up to high latitudes and waves are generated. The marginal open seas provide new opportunities and new problems. Navigation and other maritime activities become possible, but wave heights, storm surges and coastal erosion will likely increase. Air-sea interactions enter a completely new regime, with momentum, energy, heat, gas and moisture fluxes being moderated or produced by the waves, and impacting on upper-ocean mixing. All these issues require knowledge of the wave climate. We will report results of investigation of wave climate and its trends by means of satellite altimetry. This is a challenging, but important topic. On one hand, no statistical approach is possible since in the past for most of the Arctic Ocean there was limited wave activity. Extrapolations of the current observations into the future are not feasible, because ice cover and wind patterns in the Arctic are changing. On the other hand, information on the mean and extreme wave properties, such as wave height, period, direction, on the frequency of occurrence and duration of the storms is of great importance for oceanographic, meteorological, climate, naval and maritime applications in the Arctic Seas.

Atlantic Water Advection and Ice Sheet-Ocean Feedbacks in the Arctic Ocean During the Last 200 ky

NASA Astrophysics Data System (ADS)

Spielhagen, R. F.; Mackensen, A.; Stein, R. H.

2016-12-01

Earlier work on Arctic deep-sea cores from the eastern Lomonosov Ridge and the Morris Jesup Rise had revealed that large-scale Eurasian ice sheet growth was initiated at times with seasonally open waters in the Arctic Ocean, indicating a role for the ocean in nearby ice sheet development in the last 200 ky. Here we present microfossil and geochemical data from new sediment cores obtained from the western and easternmost Lomonosov Ridge during the PS87 expedition (2014) of RV Polarstern, amended by data from refined analyses of the older cores. They allow to investigate in more detail the feedbacks between Atlantic Water (AW) advection, sea ice, and ice sheets. In all cores, high microfossil abundances are found just below layers rich in iceberg-rafted detritus, supporting the hypothesis of Arctic Ocean moisture supply for the growth of Eurasian ice sheets. On the other hand, the new microfaunal results suggest that the decay of the ice sheets and the enhanced freshwater discharge to the Arctic may have influenced the routing of subsurface AW in the Arctic Ocean, at least during marine isotope (sub)stages (MIS) 5a and 5e. In the early part of these relatively mild climatic intervals, faunal and isotopic data suggest a noticable advection of Atlantic Water, yet of rather low temperature and likely at depths comparable to the modern distribution (i.e., below 150 m) or even deeper. This may be explained by a more southerly position of AW cooling and submergence than today, caused by a thick layer of low saline waters near the surface which stemmed from the slow melting of ice sheet remnants on the Eurasian continent and shelves. In the second half of both MIS 5a and 5e, AW advection was significantly stronger and may have occurred at shallower depths, as indicated by unusually large amounts of small subpolar planktic foraminifers in central Arctic sediments. AW was apparently diverted northward from the Fram Strait and spread eastward along the Lomonosov Ridge. A

An atmosphere-ocean GCM modelling study of the climate response to changing Arctic seaways in the early Cenozoic.

NASA Astrophysics Data System (ADS)

Roberts, C. D.; Legrande, A. N.; Tripati, A. K.

2008-12-01

The report of fossil Azolla (a freshwater aquatic fern) in sediments from the Lomonosov Ridge suggests low salinity conditions occurred in the Arctic Ocean in the early Eocene. Restricted passages between the Arctic Ocean and the surrounding oceans are hypothesized to have caused this Arctic freshening. We investigate this scenario using a water-isotope enabled atmosphere-ocean general circulation model with Eocene boundary conditions including 4xCO2, 7xCH4, altered bathymetry and topography, and an estimated distribution of Eocene vegetational types. In one experiment, oceanic exchange between the Arctic Ocean and other ocean basins was restricted to two shallow (~250 m) seaways, one in the North Atlantic, the Greenland-Norwegian seaway, and the second connecting the Arctic Ocean with the Tethys Ocean, the Turgai Straits. In the restricted configuration, the Greenland-Norwegian seaway was closed and exchange through the Turgai Straits was limited to a depth of ~60 m. The simulations suggest that the severe restriction of Arctic seaways in the early Eocene may have been sufficient to freshen Arctic Ocean surface waters, conducive to Azolla blooms. When exchange with the Arctic Ocean is limited, salinities in the upper several hundred meters of the water column decrease by ~10 psu. In some regions, surface salinity is within 2-3 psu of the reported maximum modern conditions tolerated by Azolla (~5 psu). In the restricted scenario, salt is stored preferentially in the North Atlantic and Tethys oceans, resulting in enhanced meridional overturning, increased poleward heat transport in the North Atlantic western boundary current, and warming of surface and intermediate waters in the North Atlantic by several degrees. Increased sensible and latent heat fluxes from the North Atlantic Ocean, combined with a reduction in cloud albedo, also lead to an increase in surface air temperature of over much of North America, Greenland and Eurasia. Our work is consistent with

Shallow methylmercury production in the marginal sea ice zone of the central Arctic Ocean

PubMed Central

Heimbürger, Lars-Eric; Sonke, Jeroen E.; Cossa, Daniel; Point, David; Lagane, Christelle; Laffont, Laure; Galfond, Benjamin T.; Nicolaus, Marcel; Rabe, Benjamin; van der Loeff, Michiel Rutgers

2015-01-01

Methylmercury (MeHg) is a neurotoxic compound that threatens wildlife and human health across the Arctic region. Though much is known about the source and dynamics of its inorganic mercury (Hg) precursor, the exact origin of the high MeHg concentrations in Arctic biota remains uncertain. Arctic coastal sediments, coastal marine waters and surface snow are known sites for MeHg production. Observations on marine Hg dynamics, however, have been restricted to the Canadian Archipelago and the Beaufort Sea (<79°N). Here we present the first central Arctic Ocean (79–90°N) profiles for total mercury (tHg) and MeHg. We find elevated tHg and MeHg concentrations in the marginal sea ice zone (81–85°N). Similar to other open ocean basins, Arctic MeHg concentration maxima also occur in the pycnocline waters, but at much shallower depths (150–200 m). The shallow MeHg maxima just below the productive surface layer possibly result in enhanced biological uptake at the base of the Arctic marine food web and may explain the elevated MeHg concentrations in Arctic biota. We suggest that Arctic warming, through thinning sea ice, extension of the seasonal sea ice zone, intensified surface ocean stratification and shifts in plankton ecodynamics, will likely lead to higher marine MeHg production. PMID:25993348

Shallow methylmercury production in the marginal sea ice zone of the central Arctic Ocean.

PubMed

Heimbürger, Lars-Eric; Sonke, Jeroen E; Cossa, Daniel; Point, David; Lagane, Christelle; Laffont, Laure; Galfond, Benjamin T; Nicolaus, Marcel; Rabe, Benjamin; van der Loeff, Michiel Rutgers

2015-05-20

Methylmercury (MeHg) is a neurotoxic compound that threatens wildlife and human health across the Arctic region. Though much is known about the source and dynamics of its inorganic mercury (Hg) precursor, the exact origin of the high MeHg concentrations in Arctic biota remains uncertain. Arctic coastal sediments, coastal marine waters and surface snow are known sites for MeHg production. Observations on marine Hg dynamics, however, have been restricted to the Canadian Archipelago and the Beaufort Sea (<79 °N). Here we present the first central Arctic Ocean (79-90 °N) profiles for total mercury (tHg) and MeHg. We find elevated tHg and MeHg concentrations in the marginal sea ice zone (81-85 °N). Similar to other open ocean basins, Arctic MeHg concentration maxima also occur in the pycnocline waters, but at much shallower depths (150-200 m). The shallow MeHg maxima just below the productive surface layer possibly result in enhanced biological uptake at the base of the Arctic marine food web and may explain the elevated MeHg concentrations in Arctic biota. We suggest that Arctic warming, through thinning sea ice, extension of the seasonal sea ice zone, intensified surface ocean stratification and shifts in plankton ecodynamics, will likely lead to higher marine MeHg production.

Research Applications of Data from Arctic Ocean Drifting Platforms: The Arctic Buoy Program and the Environmental Working Group CD's.

NASA Astrophysics Data System (ADS)

Moritz, R. E.; Rigor, I.

2006-12-01

ABSTRACT: The Arctic Buoy Program was initiated in 1978 to measure surface air pressure, surface temperature and sea-ice motion in the Arctic Ocean, on the space and time scales of synoptic weather systems, and to make the data available for research, forecasting and operations. The program, subsequently renamed the International Arctic Buoy Programme (IABP), has endured and expanded over the past 28 years. A hallmark of the IABP is the production, dissemination and archival of research-quality datasets and analyses. These datasets have been used by the authors of over 500 papers on meteorolgy, sea-ice physics, oceanography, air-sea interactions, climate, remote sensing and other topics. Elements of the IABP are described briefly, including measurements, analysis, data dissemination and data archival. Selected highlights of the research applications are reviewed, including ice dynamics, ocean-ice modeling, low-frequency variability of Arctic air-sea-ice circulation, and recent changes in the age, thickness and extent of Arctic Sea-ice. The extended temporal coverage of the data disseminated on the Environmental Working Group CD's is important for interpreting results in the context of climate.

Trends in Arctic Ocean bottom pressure, sea surface height and freshwater content using GRACE and the ice-ocean model PIOMAS from 2008-2012

NASA Astrophysics Data System (ADS)

Peralta-Ferriz, Cecilia; Morison, James; Zhang, Jinlun; Bonin, Jennifer

2014-05-01

The variability of ocean bottom pressure (OBP) in the Arctic is dominated by the variations in sea surface height (SSH) from daily to monthly timescales. Conversely, OBP variability is dominated by the changes in the steric pressure (StP) at inter-annual timescales, particularly off the continental shelves. The combination of GRACE-derived ocean bottom pressure and ICESat altimetry-derived sea surface height variations in the Arctic Ocean have provided new means of identifying inter-annual trends in StP (StP = OBP-SSH) and associated freshwater content (FWC) of the Arctic region (Morison et al., 2012). Morison et al. (2012) showed that from 2004 to 2008, the FWC increased in the Beaufort Gyre and decreased in the Siberian and Central Arctic, resulting in a relatively small net basin-averaged FWC change. In this work, we investigate the inter-annual trends from 2008 to 2012 in OBP from GRACE, SSH from the state-of-the-art pan-Arctic ocean model PIOMAS -validated with tide and pressure gauges in the Arctic-, and compute the trends in StP and FWC from 2008-2012. We compare these results with the previous trends from 2005-2008 described in Morison et al. (2012). Our initial findings suggest increased salinity in the entire Arctic basin (relative to the climatological seasonal variation) from 2008-2012, compared to the preceding four years (2005-2008). We also find that the trends in OBP, SSH and StP from 2008-2012 present a different behavior during the spring-summer and fall-winter, unlike 2005-2008, in which the trends were generally consistent through all months of the year. It seems since 2009, when the Beaufort Gyre relaxed and the export of freshwater from the Canada Basin into the Canadian Archipelago and Fram Strait, via the Lincoln Sea, was anomalously large (de Steur et al., 2013), the Arctic Ocean has entered a new circulation regime. The causes of such changes in the inter-annual trends of OBP, SSH and StP -hence FWC-, associated with the changes in the

Integrating surface and mantle constraints for palaeo-ocean evolution: a tour of the Arctic and adjacent regions (Arne Richter Award for Outstanding Young Scientists Lecture)

NASA Astrophysics Data System (ADS)

Shephard, Grace E.

2016-04-01

Plate tectonic reconstructions heavily rely on absolute motions derived from hotspot trails or palaeomagnetic data and ocean-floor magnetic anomaies and fracture-zone geometries to constrain the detailed history of ocean basins. However, as oceanic lithosphere is progressively recycled into the mantle, kinematic data regarding the history of these now extinct-oceans is lost. In order to better understand their evolution, novel workflows, which integrate a wide range of complementary yet independent geological and geophysical datasets from both the surface and deep mantle, must be utilised. In particular, the emergence of time-dependent, semi or self-consistent geodynamic models of ever-increasing temporal and spatial resolution are revealing some critical constraints on the evolution and fate of oceanic slabs. The tectonic evolution of the circum-Arctic is no exception; since the breakup of Pangea, this enigmatic region has seen major plate reorganizations and the opening and closure of several ocean basins. At the surface, a myriad of potential kinematic scenarios including polarity, timing, geometry and location of subduction have emerged, including for systems along continental margins and intra-oceanic settings. Furthermore, recent work has reignited a debate about the origins of 'anchor' slabs, such as the Farallon and Mongol-Okhotsk slabs, which have been used to refine absolute plate motions. Moving to the mantle, seismic tomography models reveal a region peppered with inferred slabs, however assumptions about their affinities and subduction location, timing, geometry and polarity are often made in isolation. Here, by integrating regional plate reconstructions with insights from seismic tomography, satellite derived gravity gradients, slab sinking rates and geochemistry, I explore some Mesozoic examples from the palaeo-Arctic, northern Panthalassa and western margin of North America, including evidence for a discrete and previously undescribed slab under

Geochemistry and Flux of Terrigenous Dissolved Organic Matter to the Arctic Ocean

NASA Astrophysics Data System (ADS)

Spencer, R. G.; Mann, P. J.; Hernes, P. J.; Tank, S. E.; Striegl, R. G.; Dyda, R. Y.; Peterson, B. J.; McClelland, J. W.; Holmes, R. M.

2011-12-01

Rivers draining into the Arctic Ocean exhibit high concentrations of terrigenous dissolved organic carbon (DOC) and recent studies indicate that DOC export is changing due to climatic warming and alteration in permafrost condition. The fate of exported DOC in the Arctic Ocean is of key importance for understanding the regional carbon cycle and remains a point of discussion in the literature. As part of the Arctic Great Rivers Observatory (Arctic-GRO) project, samples were collected for DOC, chromophoric dissolved organic matter (CDOM) and lignin phenols from the Ob', Yenisey, Lena, Kolyma, Mackenzie and Yukon rivers in 2009 - 2010. DOC and lignin concentrations were elevated during the spring freshet and measurements related to DOC composition indicated an increasing contribution from terrestrial vascular plant sources at this time of year (e.g. lignin carbon-normalized yield, CDOM spectral slope, SUVA254, humic-like fluorescence). CDOM absorption was found to correlate strongly with both DOC (r2=0.83) and lignin concentration (r2=0.92) across the major arctic rivers. Utilizing these relationships we modeled loads for DOC and lignin export from high-resolution CDOM measurements (daily across the freshet) to derive improved flux estimates, particularly from the dynamic spring discharge maxima period when the majority of DOC and lignin export occurs. The new load estimates for DOC and lignin are higher than previous evaluations, emphasizing that if these are more representative of current arctic riverine export, terrigenous DOC is transiting through the Arctic Ocean at a faster rate than previously thought. It is apparent that higher resolution sampling of arctic rivers is exceptionally valuable with respect to deriving accurate fluxes and we highlight the potential of CDOM in this role for future studies and the applicability of in-situ CDOM sensors.

Arctic and N Atlantic Crustal Thickness and Oceanic Lithosphere Distribution from Gravity Inversion

NASA Astrophysics Data System (ADS)

Kusznir, Nick; Alvey, Andy

2014-05-01

The ocean basins of the Arctic and N. Atlantic formed during the Mesozoic and Cenozoic as a series of distinct ocean basins, both small and large, leading to a complex distribution of oceanic crust, thinned continental crust and rifted continental margins. The plate tectonic framework of this region was demonstrated by the pioneering work of Peter Ziegler in AAPG Memoir 43 " Evolution of the Arctic-North Atlantic and the Western Tethys" published in 1988. The spatial evolution of Arctic Ocean and N Atlantic ocean basin geometry and bathymetry are critical not only for hydrocarbon exploration but also for understanding regional palaeo-oceanography and ocean gateway connectivity, and its influence on global climate. Mapping crustal thickness and oceanic lithosphere distribution represents a substantial challenge for the Polar Regions. Using gravity anomaly inversion we have produced comprehensive maps of crustal thickness and oceanic lithosphere distribution for the Arctic and N Atlantic region, We determine Moho depth, crustal basement thickness, continental lithosphere thinning and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir 2008). Gravity anomaly and bathymetry data used in the gravity inversion are from the NGA (U) Arctic Gravity Project and IBCAO respectively; sediment thickness is from a new regional compilation. The resulting maps of crustal thickness and continental lithosphere thinning factor are used to determine continent-ocean boundary location and the distribution of oceanic lithosphere. Crustal cross-sections using Moho depth from the gravity inversion allow continent-ocean transition structure to be determined and magmatic type (magma poor, "normal" or magma rich). Our gravity inversion predicts thin crust and high continental lithosphere thinning factors in the Eurasia, Canada, Makarov, Podvodnikov and Baffin Basins

Arctic Ocean sea ice cover during the penultimate glacial and the last interglacial.

PubMed

Stein, Ruediger; Fahl, Kirsten; Gierz, Paul; Niessen, Frank; Lohmann, Gerrit

2017-08-29

Coinciding with global warming, Arctic sea ice has rapidly decreased during the last four decades and climate scenarios suggest that sea ice may completely disappear during summer within the next about 50-100 years. Here we produce Arctic sea ice biomarker proxy records for the penultimate glacial (Marine Isotope Stage 6) and the subsequent last interglacial (Marine Isotope Stage 5e). The latter is a time interval when the high latitudes were significantly warmer than today. We document that even under such warmer climate conditions, sea ice existed in the central Arctic Ocean during summer, whereas sea ice was significantly reduced along the Barents Sea continental margin influenced by Atlantic Water inflow. Our proxy reconstruction of the last interglacial sea ice cover is supported by climate simulations, although some proxy data/model inconsistencies still exist. During late Marine Isotope Stage 6, polynya-type conditions occurred off the major ice sheets along the northern Barents and East Siberian continental margins, contradicting a giant Marine Isotope Stage 6 ice shelf that covered the entire Arctic Ocean.Coinciding with global warming, Arctic sea ice has rapidly decreased during the last four decades. Here, using biomarker records, the authors show that permanent sea ice was still present in the central Arctic Ocean during the last interglacial, when high latitudes were warmer than present.

Problems of Tectonics and Tectonic Evolution of the Arctic

NASA Astrophysics Data System (ADS)

Vernikovskiy, V. A.; Metelkin, D. V.; Matushkin, N. Y.; Vernikovskaya, A. E.; Chernova, A. I.; Mikhaltsov, N. E.

2017-12-01

The Arctic Ocean within Russia remains poorly investigated area, in particular to geological structures and the Arctic Ocean floor. Many researchers believe that the basements of the terranes, composing the Arctic shelf and continental slopes, are of the Precambrian age. It was assumed that the Arctic terranes formed the ancient paleocontinent of Arctida that broke up during rifting, whereas the separated plates and terranes accreted to the periphery of the Arctic Ocean at a later stage. However, geological, geochronological and paleomagnetic evidence to test this assumption has been insufficient. Recently, geological and geophysical studies have significantly increased, in particular to the structures of Eastern Arctic. For example, the New Siberian Islands Archipelago is one of key structures for understanding geology and evolution of the Arctic region. Additionally, several submerged structures containing fragments of continental crust, including the Lomonosov Ridge and the Mendeleev Rise, are identified within the Arctic Ocean and adjacent to the New Siberian Islands Archipelago. Here we present new geochronological and paleomagnetic data to refine the evolution of the Arctida paleocontinent. Our model implies existence of the two Arctidas during Late Precambrian - Late Paleozoic. The earlier Arctida-I was located near equator and connected with the continental margins of Laurentia, Baltica and Siberia within the supercontinent of Rodinia. The initiation of Arctida-I rifting is associated with breakup of Rodinia. As a result, small plates, including Svalbard, Kara, New Siberia Island and other terranes, were formed. We have reconstructed the main stages of further remobilization and global drift of these plates before Pangea assemblage. We assume that the later Arctida-II was located at the Pangean periphery in the temperate latitudes, and was also connected to the Laurentia, Baltica, and Siberia cratons. The breakup of the Arctida-II is suggested to have

Ice-tethered measurement platforms in the Arctic Ocean: a contribution by the FRAM infrastructure program

NASA Astrophysics Data System (ADS)

Hoppmann, Mario; Nicolaus, Marcel; Rabe, Benjamin; Wenzhöfer, Frank; Katlein, Christian; Scholz, Daniel

2016-04-01

The Arctic Ocean has been in the focus of many studies during recent years, investigating the state, the causes and the implications of the observed rapid transition towards a thinner and younger sea-ice cover. However, consistent observational datasets of sea ice, ocean and atmosphere are still sparse due to the limited accessibility and harsh environmental conditions. One important tool to fill this gap has become more and more feasible during recent years: autonomous, ice-tethered measurement platforms (buoys). These drifting instruments independently transmit their data via satellites, and enable observations over larger areas and over longer time periods than manned expeditions, even throughout the winter. One aim of the newly established FRAM (FRontiers in Arctic marine Monitoring) infrastructure program at the Alfred-Wegener-Institute is to realize and maintain an interdisciplinary network of buoys in the Arctic Ocean, contributing to an integrated, Arctic-wide observatory. The additional buoy infrastructure, ship-time, and developments provided by FRAM are critical elements in the ongoing international effort to fill the large data gaps in a rapidly changing Arctic Ocean. Our focus is the particularly underrepresented Eurasian Basin. Types of instruments range from snow depth beacons and ice mass balance buoys for monitoring ice growth and snow accumulation, over radiation and weather stations for energy budget estimates, to ice-tethered profiling systems for upper ocean monitoring. Further, development of new bio-optical and biogeochemical buoys is expected to enhance our understanding of bio-physical processes associated with Arctic sea ice. The first set of FRAM buoys was deployed in September 2015 from RV Polarstern. All datasets are publicly available on dedicated web portals. Near real time data are reported into international initiatives, such as the Global Telecommunication System (GTS) and the International Arctic Buoy Programme (IABP). The

Extensive under-ice turbulence microstructure measurements in the central Arctic Ocean in 2015

NASA Astrophysics Data System (ADS)

Rabe, Benjamin; Janout, Markus; Graupner, Rainer; Hoelemann, Jens; Hampe, Hendrik; Hoppmann, Mario; Horn, Myriel; Juhls, Bennet; Korhonen, Meri; Nikolopoulos, Anna; Pisarev, Sergey; Randelhoff, Achim; Savy, John-Philippe; Villacieros, Nicolas

2016-04-01

The Arctic Ocean is a strongly stratified low-energy environment, where tides are weak and the upper ocean is protected by an ice cover during much of the year. Interior mixing processes are dominated by double diffusion. The upper Arctic Ocean features a cold surface mixed layer, which, separated by a sharp halocline, protects the sea ice from the warmer underlying Atlantic- and Pacific-derived water masses. These water masses carry nutrients that are important for the Arctic ecosystem. Hence vertical fluxes of heat, salt, and nutrients are crucial components in understanding the Arctic ecosystem. Yet, direct flux measurements are difficult to obtain and hence sparse. In 2015, two multidisciplinary R/V Polarstern expeditions to the Arctic Ocean resulted in a series of under-ice turbulence microstructure measurements. These cover different locations across the Eurasian and Makarov Basins, during the melt season in spring and early summer as well as during freeze-up in late summer. Sampling was carried out from ice floes with repeated profiles resulting in 4-24 hour-long time series. 2015 featured anomalously warm atmospheric conditions during summer followed by unusually low temperatures in September. Our measurements show elevated dissipation rates at the base of the mixed layer throughout all stations, with significantly higher levels above the Eurasian continental slope when compared with the Arctic Basin. Additional peaks were found between the mixed layer and the halocline, in particular at stations where Pacific Summer water was present. This contribution provides first flux estimates and presents first conclusions regarding the impact of atmospheric and sea ice conditions on vertical mixing in 2015.

Taxonomic revision of deep-sea Ostracoda from the Arctic Ocean

USGS Publications Warehouse

Yasuhara, Moriaki; Stepanova, Anna; Okahashi, Hisayo; Cronin, Thomas M.; Brouwers, Elisabeth M.

2015-01-01

Taxonomic revision of deep-sea Ostracoda from the Arctic Ocean was conducted to reduce taxonomic uncertainty that will improve our understanding of species ecology, biogeography and relationship to faunas from other deep-sea regions. Fifteen genera and 40 species were examined and (re-)illustrated with high-resolution scanning electron microscopy images, covering most of known deep-sea species in the central Arctic Ocean. Seven new species are described: Bythoceratina lomonosovensis n. sp., Cytheropteron parahamatum n. sp., Cytheropteron lanceae n. sp.,Cytheropteron irizukii n. sp., Pedicythere arctica n. sp., Cluthiawhatleyi n. sp., Krithe hunti n. sp. This study provides a robust taxonomic baseline for application to paleoceanographical reconstruction and biodiversity analyses in this climatically sensitive region.

Enhanced role of eddies in the Arctic marine biological pump

PubMed Central

Watanabe, Eiji; Onodera, Jonaotaro; Harada, Naomi; Honda, Makio C.; Kimoto, Katsunori; Kikuchi, Takashi; Nishino, Shigeto; Matsuno, Kohei; Yamaguchi, Atsushi; Ishida, Akio; Kishi, Michio J.

2014-01-01

The future conditions of Arctic sea ice and marine ecosystems are of interest not only to climate scientists, but also to economic and governmental bodies. However, the lack of widespread, year-long biogeochemical observations remains an obstacle to understanding the complicated variability of the Arctic marine biological pump. Here we show an early winter maximum of sinking biogenic flux in the western Arctic Ocean and illustrate the importance of shelf-break eddies to biological pumping from wide shelves to adjacent deep basins using a combination of year-long mooring observations and three-dimensional numerical modelling. The sinking flux trapped in the present study included considerable fresh organic material with soft tissues and was an order of magnitude larger than previous estimates. We predict that further reductions in sea ice will promote the entry of Pacific-origin biological species into the Arctic basin and accelerate biogeochemical cycles connecting the Arctic and subarctic oceans. PMID:24862402

Impacts of Ocean Acidification on Sediment Processes in Shallow Waters of the Arctic Ocean

PubMed Central

Gazeau, Frédéric; van Rijswijk, Pieter; Pozzato, Lara; Middelburg, Jack J.

2014-01-01

Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer waters, acidification rates in these areas are faster than those in sub-tropical regions. The present study investigates the effects of ocean acidification on sediment composition, processes and sediment-water fluxes in an Arctic coastal system. Undisturbed sediment cores, exempt of large dwelling organisms, were collected, incubated for a period of 14 days, and subject to a gradient of pCO2 covering the range of values projected for the end of the century. On five occasions during the experimental period, the sediment cores were isolated for flux measurements (oxygen, alkalinity, dissolved inorganic carbon, ammonium, nitrate, nitrite, phosphate and silicate). At the end of the experimental period, denitrification rates were measured and sediment samples were taken at several depth intervals for solid-phase analyses. Most of the parameters and processes (i.e. mineralization, denitrification) investigated showed no relationship with the overlying seawater pH, suggesting that ocean acidification will have limited impacts on the microbial activity and associated sediment-water fluxes on Arctic shelves, in the absence of active bio-irrigating organisms. Only following a pH decrease of 1 pH unit, not foreseen in the coming 300 years, significant enhancements of calcium carbonate dissolution and anammox rates were observed. Longer-term experiments on different sediment types are still required to confirm the limited impact of ocean acidification on shallow Arctic sediment processes as observed in this study. PMID:24718610

Impacts of ocean acidification on sediment processes in shallow waters of the Arctic Ocean.

PubMed

Gazeau, Frédéric; van Rijswijk, Pieter; Pozzato, Lara; Middelburg, Jack J

2014-01-01

Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer waters, acidification rates in these areas are faster than those in sub-tropical regions. The present study investigates the effects of ocean acidification on sediment composition, processes and sediment-water fluxes in an Arctic coastal system. Undisturbed sediment cores, exempt of large dwelling organisms, were collected, incubated for a period of 14 days, and subject to a gradient of pCO2 covering the range of values projected for the end of the century. On five occasions during the experimental period, the sediment cores were isolated for flux measurements (oxygen, alkalinity, dissolved inorganic carbon, ammonium, nitrate, nitrite, phosphate and silicate). At the end of the experimental period, denitrification rates were measured and sediment samples were taken at several depth intervals for solid-phase analyses. Most of the parameters and processes (i.e. mineralization, denitrification) investigated showed no relationship with the overlying seawater pH, suggesting that ocean acidification will have limited impacts on the microbial activity and associated sediment-water fluxes on Arctic shelves, in the absence of active bio-irrigating organisms. Only following a pH decrease of 1 pH unit, not foreseen in the coming 300 years, significant enhancements of calcium carbonate dissolution and anammox rates were observed. Longer-term experiments on different sediment types are still required to confirm the limited impact of ocean acidification on shallow Arctic sediment processes as observed in this study.

Variation of atmospheric carbon monoxide over the Arctic Ocean during summer 2012

NASA Astrophysics Data System (ADS)

Park, Keyhong; Siek Rhee, Tae; Emmons, Louisa

2014-05-01

Atmospheric carbon monoxide (CO) plays an important role in ozone-related chemistry in the troposphere, especially under low-NOx conditions like the open ocean. During summer 2012, we performed a continuous high-resolution (0.1Hz) shipboard measurement of atmospheric CO over the Arctic Ocean. We also simulated the observation using a 3-D global chemical transport model (the Model for OZone And Related chemical Tracers-4; MOZART-4) for further analysis of the observed results. In the model, tags for each sources and emission regions of CO are applied and this enables us to delineate the source composition of the observations. Along with the observed variation of CO concentration during the research cruise, we will present in detailed analysis of the variation of source components and change of regional contributions. We found large (~80ppbv) variation of CO concentration in the Arctic Ocean which is mostly influenced by the variation of biomass burning activity. The contribution of anthropogenic emission is limited over the Arctic Ocean, although the northeast Asian anthropogenic emission shows a dominant component of transported anthropogenic CO. Also, our analysis shows, near the Bering Strait, Europe is the main emission region for anthropogenic CO.

Arctic Sea Ice Basal Melt Onset Variability and Associated Ocean Surface Heating

NASA Astrophysics Data System (ADS)

Merrick, R. A.; Hutchings, J. K.

2015-12-01

The interannual and regional variability in Arctic sea ice melt has previously been characterized only in terms of surface melting. A focus on the variability in the onset of basal melt is additionally required to understand Arctic melt patterns. Monitoring basal melt provides a glimpse into the importance of ocean heating to sea ice melt. This warming is predominantly through seawater exposure due to lead opening and the associated solar warming at the ocean's surface. We present the temporal variability in basal melt onset observed by ice mass balance buoys throughout the Arctic Ocean since 2003, providing a different perspective than the satellite microwave data used to measure the onset of surface melt. We found that melt onset varies greatly, even for buoys deployed within 100km of each other. Therefore large volumes of data are necessary to accurately estimate the variability of basal melt onset. Once the variability of basal melt onset has been identified, we can investigate how this range has been changing as a response to atmospheric and oceanic warming, changes in ice morphology as well as the intensification of the ice albedo feedback.

Arctic Submarine Slope Stability

NASA Astrophysics Data System (ADS)

Winkelmann, D.; Geissler, W.

2010-12-01

the consequence. Its geometrical configuration and timing is different from submarine slides on other glaciated continental margins. Thus, it raises the question whether slope stability within the Arctic Ocean is governed by processes specific to this environment. The extraordinary thick slabs (up to 1600 m) that were moved translationally during sliding rise the question on the nature of the weak layers associated with this process. Especially theories involving higher pore pressure are being challenged by this observation, because either extreme pore pressures or alternative explanations (e.g. mineralogical and/or textural) can be considered. To assess the actual submarine slope stability and failure potential in the Arctic Ocean, we propose to drill and recover weak layer material of the HYM from the adjacent intact strata by deep drilling under the framework of Integrated Ocean Drilling Program. This is the only method to recover weak layer material from the HYM, because the strata are too thick. We further propose to drill into the adjacent deforming slope to identify material properties of the layers acting as detachment and monitor the deformation.

Orbital-scale Central Arctic Ocean Temperature Records from Benthic Foraminiferal δ18O and Ostracode Mg/Ca Ratios

NASA Astrophysics Data System (ADS)

Keller, K.; Cronin, T. M.; Dwyer, G. S.; Farmer, J. R.; Poirier, R. K.; Schaller, M. F.

2017-12-01

Orbital-scale climate variability is often amplified in the polar region, for example in changes in seawater temperature, sea-ice cover, deep-water formation, ecosystems, heat storage and carbon cycling. Yet, the relationship between the Arctic Ocean and global climate remains poorly understood due largely to limited orbital-scale paleoclimate records, the complicated nature of sea-ice response to climate and limited abundance of deep sea biological proxies. Here we reconstruct central Arctic Ocean bottom temperatures over the last 600 kyr using ostracode Mg/Ca ratios (genus Krithe) and benthic foraminiferal oxygen isotope ratios (δ18Obf - I. teretis, O. tener, P. bulloides, C. reniforme, C. wuellerstorfi) in six sediment cores recovered from the Mendeleev and Northwind Ridges (700- 2726 m water depth). We examined glacial-interglacial cycles in Arctic seawater temperatures and Arctic δ18Obf chronostratigraphy to reconcile effects of changing bottom water temperature, ice volume and regional hydrography on δ18Obf records. Results show lower ( 10-12 mmol/mol) interglacial and higher ( 16-23 mmol/mol) glacial Mg/Ca ratios, signifying intermediate depth ocean warming during glacials of up to 2 ºC. These temperature maxima are likely related to a deepening of the halocline and the corresponding deeper influence of warm Atlantic water. Glacial-interglacial δ18Obf ranges are smaller in the Arctic ( 0.8-1‰ VPDB) than in the global ocean ( 1.8 ‰). However, when the distinct glacial-interglacial temperature histories of the Arctic (glacial warming) and global ocean (glacial cooling) are accounted for, both Arctic and global ocean seawater δ18O values (δ18Osw) exhibit similar 1.2-1.3 ‰ glacial-interglacial ranges. Thus, Arctic δ18Obf confirms glacial Arctic warming inferred from ostracode Mg/Ca. This study will discuss the strengths and limitations of applying paired Mg/Ca and oxygen isotope proxies in reconstructing more robust paleoceanographic changes in the

Mid-Cenozoic tectonic and paleoenvironmental setting of the central Arctic Ocean

USGS Publications Warehouse

O'Regan, M.; Moran, K.; Backman, J.; Jakobsson, M.; Sangiorgi, F.; Brinkhuis, Henk; Pockalny, Rob; Skelton, Alasdair; Stickley, Catherine E.; Koc, N.; Brumsack, Hans-Juergen; Willard, Debra A.

2008-01-01

Drilling results from the Integrated Ocean Drilling Program's Arctic Coring Expedition (ACEX) to the Lomonosov Ridge (LR) document a 26 million year hiatus that separates freshwater-influenced biosilica-rich deposits of the middle Eocene from fossil-poor glaciomarine silty clays of the early Miocene. Detailed micropaleontological and sedimentological data from sediments surrounding this mid-Cenozoic hiatus describe a shallow water setting for the LR, a finding that conflicts with predrilling seismic predictions and an initial postcruise assessment of its subsidence history that assumed smooth thermally controlled subsidence following rifting. A review of Cenozoic tectonic processes affecting the geodynamic evolution of the central Arctic Ocean highlights a prolonged phase of basin-wide compression that ended in the early Miocene. The coincidence in timing between the end of compression and the start of rapid early Miocene subsidence provides a compelling link between these observations and similarly accounts for the shallow water setting that persisted more than 30 million years after rifting ended. However, for much of the late Paleogene and early Neogene, tectonic reconstructions of the Arctic Ocean describe a landlocked basin, adding additional uncertainty to reconstructions of paleodepth estimates as the magnitude of regional sea level variations remains unknown.

Calcareous microfossil-based orbital cyclostratigraphy in the Arctic Ocean

USGS Publications Warehouse

Marzen, Rachel; DeNinno, Lauren H.; Cronin, Thomas M.

2016-01-01

Microfaunal and geochemical proxies from marine sediment records from central Arctic Ocean (CAO) submarine ridges suggest a close relationship over the last 550 thousand years (kyr) between orbital-scale climatic oscillations, sea-ice cover, marine biological productivity and other parameters. Multiple paleoclimate proxies record glacial to interglacial cycles. To understand the climate-cryosphere-productivity relationship, we examined the cyclostratigraphy of calcareous microfossils and constructed a composite Arctic Paleoclimate Index (API) "stack" from benthic foraminiferal and ostracode density from 14 sediment cores. Following the hypothesis that API is driven mainly by changes in sea-ice related productivity, the API stack shows the Arctic experienced a series of highly productive interglacials and interstadials every ∼20 kyr. These periods signify minimal ice shelf and sea-ice cover and maximum marine productivity. Rapid transitions in productivity are seen during shifts from interglacial to glacial climate states. Discrepancies between the Arctic API curves and various global climatic, sea-level and ice-volume curves suggest abrupt growth and decay of Arctic ice shelves related to climatic and sea level oscillations.

Preliminary design for Arctic atmospheric radiative transfer experiments

NASA Technical Reports Server (NTRS)

Zak, B. D.; Church, H. W.; Stamnes, K.; Shaw, G.; Filyushkin, V.; Jin, Z.; Ellingson, R. G.; Tsay, S. C.

1995-01-01

If current plans are realized, within the next few years, an extraordinary set of coordinated research efforts focusing on energy flows in the Arctic will be implemented. All are motivated by the prospect of global climate change. SHEBA (Surface Energy Budget of the Arctic Ocean), led by the National Science Foundation (NSF) and the Office of Naval Research (ONR), involves instrumenting an ice camp in the perennial Arctic ice pack, and taking data for 12-18 months. The ARM (Atmospheric Radiation Measurement) North Slope of Alaska and Adjacent Arctic Ocean (NSA/AAO) Cloud and Radiation Testbed (CART) focuses on atmospheric radiative transport, especially in the presence of clouds. The NSA/AAO CART involves instrumenting a sizeable area on the North Slope of Alaska and adjacent waters in the vicinity of Barrow, and acquiring data over a period of about 10 years. FIRE (First ISCCP (International Satellite Cloud Climatology Program) Regional Experiment) Phase 3 is a program led by the National Aeronautics and Space Administration (NASA) which focuses on Arctic clouds, and which is coordinated with SHEBA and ARM. FIRE has historically emphasized data from airborne and satellite platforms. All three program anticipate initiating Arctic data acquisition during spring, 1997. In light of his historic opportunity, the authors discuss a strawman atmospheric radiative transfer experimental plan that identifies which features of the radiative transport models they think should be tested, what experimental data are required for each type of test, the platforms and instrumentation necessary to acquire those data, and in general terms, how the experiments could be conducted. Aspects of the plan are applicable to all three programs.

77 FR 2513 - Draft Environmental Impact Statement for Effects of Oil and Gas Activities in the Arctic Ocean

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-18

... Environmental Impact Statement for Effects of Oil and Gas Activities in the Arctic Ocean AGENCY: National Marine... Environmental Impact Statement (DEIS) for the Effects of Oil and Gas Activities in the Arctic Ocean.'' Based on... Web page at: http://www.nmfs.noaa.gov/pr/permits/eis/arctic.htm . FOR FURTHER INFORMATION CONTACT...

Arctic Contribution to Upper-Ocean Variability in the North Atlantic.

NASA Astrophysics Data System (ADS)

Walsh, John E.; Chapman, William L.

1990-12-01

Because much of the deep water of the world's oceans forms in the high-latitude North Atlantic, the potential climatic leverage of salinity and temperature anomalies in this region is large. Substantial variations of sea ice have accompanied North Atlantic salinity and temperature anomalies, especially the extreme and long-lived `Great Salinity Anomaly' of the late 1960s and early 1970s. Atmospheric pressure data are used hem to show that the local forcing of high-latitude North Atlantic Ocean fluctuations is augmented by antecedent atmospheric circulation anomalies over the central Arctic. These circulation anomalies are consistent with enhanced wind-forcing of thicker, older ice into the Transpolar Drift Stream and an enhanced export of sea ice (fresh water) from the Arctic into the Greenland Sea prior to major episodes of ice severity in the Greenland and Iceland seas. An index of the pressure difference between southern Greenland and the Arctic-Asian coast reached its highest value of the twentieth century during the middle-to-late 1960s, the approximate time of the earliest observation documentation of the Great Salinity Anomaly.

Factors driving mercury variability in the Arctic atmosphere and ocean over the past 30 years

NASA Astrophysics Data System (ADS)

Fisher, Jenny A.; Jacob, Daniel J.; Soerensen, Anne L.; Amos, Helen M.; Corbitt, Elizabeth S.; Streets, David G.; Wang, Qiaoqiao; Yantosca, Robert M.; Sunderland, Elsie M.

2013-12-01

observations at Arctic sites (Alert and Zeppelin) show large interannual variability (IAV) in atmospheric mercury (Hg), implying a strong sensitivity of Hg to environmental factors and potentially to climate change. We use the GEOS-Chem global biogeochemical Hg model to interpret these observations and identify the principal drivers of spring and summer IAV in the Arctic atmosphere and surface ocean from 1979-2008. The model has moderate skill in simulating the observed atmospheric IAV at the two sites (r 0.4) and successfully reproduces a long-term shift at Alert in the timing of the spring minimum from May to April (r = 0.7). Principal component analysis indicates that much of the IAV in the model can be explained by a single climate mode with high temperatures, low sea ice fraction, low cloudiness, and shallow boundary layer. This mode drives decreased bromine-driven deposition in spring and increased ocean evasion in summer. In the Arctic surface ocean, we find that the IAV for modeled total Hg is dominated by the meltwater flux of Hg previously deposited to sea ice, which is largest in years with high solar radiation (clear skies) and cold spring air temperature. Climate change in the Arctic is projected to result in increased cloudiness and strong warming in spring, which may thus lead to decreased Hg inputs to the Arctic Ocean. The effect of climate change on Hg discharges from Arctic rivers remains a major source of uncertainty.

Sources of Arctic Ocean upper halocline and changes in its properties

NASA Astrophysics Data System (ADS)

Anderson, L. G.; Andersson, P. S.; Bjvrk, G. M.; Jutterstrom, S.; Wahlstrom, I.

2011-12-01

The upper halocline of the Arctic Ocean has a distinct chemical signature by its high nutrient and partial pressure of carbon dioxide as well as low oxygen and pH values. This signature is formed along the bottoms of the Siberian shelf seas, primarily the Chukchi and East Siberian Seas, by a combination of mineralization of organic matter and release of the decay products to the sea ice brine enriched bottom water. In this contribution we use salinity and total alkalinity data to show that the fraction of sea ice brine in the nutrient enriched upper halocline water in the central Arctic Ocean is up to 4%. This water of low pH, and thus also low in calcium carbonate solubility, is found between about 100 and 200 m depth and is thus close to the productive surface water in a future central Arctic Ocean of less summer sea ice cover. In the East Siberian Sea the bottom waters with exceptional high nutrient concentration and low pH have typically between 5 and 10% of sea ice brine as computed form salinity and oxygen-18 vales. On the continental slope, over bottom depths of 15-200 m, the brine contribution was 6% at the nutrient maximum depth (50-100 m). At the same location as well as over deeper waters the silicate maximum was found over a wider salinity range than traditionally, in agreement with observations of Nishino et al (J. Oceanogr, Vol. 65, pp. 871 to 883, 2009) in the area of the deep Arctic Ocean east of the Chukchi Plateau. However, the water with lowest salinity (~32.5) in the silicate maximum had maximum in nitrate deficit expressed as N** (= [NO3] - 16[PO4] + 2.9) and the waters with highest salinity (~34.5) had the lowest oxygen concentration. This pattern is not obvious and point to at least two different biochemical environments within the East Siberian Sea that has not been observed before and could be a sign of a changing marine climate in the East Siberian Sea. One cause could be more open water in the summer season followed by more sea ice

Aerosol Microphysical Effects on Cloud Fraction over the Nighttime Arctic Ocean

NASA Astrophysics Data System (ADS)

Zamora, L. M.; Kahn, R. A.; Stohl, A.; Eckhardt, S.

2017-12-01

Cloud fraction is a key component affecting the surface energy balance in the Arctic. Aerosol microphysical processes can affect cloud fraction, for example through cloud lifetime effects. However, the importance of aerosol impacts on cloud fraction is not well constrained on a regional scale at high latitudes. Here we discuss a new method for identifying and comparing clean and aerosol-influenced cloud characteristics using a combination of multi-year remote sensing data (CALIPSO, CloudSat) and the FLEXPART aerosol model. We use this method to investigate a variety of aerosol microphysical impacts on nighttime Arctic Ocean clouds on regional and local scales. We observe differences in factors that can impact cloud lifetime, including cloud thickness and phase, within a subset of clean vs. polluted clouds. We will also discuss cumulative cloud fraction differences in clean and non-clean environments, as well as their likely impact on longwave cloud radiative effects at the Arctic Ocean surface during polar night.

DNA barcoding of Arctic Ocean holozooplankton for species identification and recognition

NASA Astrophysics Data System (ADS)

Bucklin, Ann; Hopcroft, Russell R.; Kosobokova, Ksenia N.; Nigro, Lisa M.; Ortman, Brian D.; Jennings, Robert M.; Sweetman, Christopher J.

2010-01-01

Zooplankton species diversity and distribution are important measures of environmental change in the Arctic Ocean, and may serve as 'rapid-responders' of climate-induced changes in this fragile ecosystem. The scarcity of taxonomists hampers detailed and up-to-date monitoring of these patterns for the rarer and more problematic species. DNA barcodes (short DNA sequences for species recognition and discovery) provide an alternative approach to accurate identification of known species, and can speed routine analysis of zooplankton samples. During 2004-2008, zooplankton samples were collected during cruises to the central Arctic Ocean and Chukchi Sea. A ˜700 base-pair region of the mitochondrial cytochrome oxidase I (mtCOI) gene was amplified and sequenced for 82 identified specimens of 41 species, including cnidarians (six hydrozoans, one scyphozoan), arthropod crustaceans (five amphipods, 24 copepods, one decapod, and one euphausiid); two chaetognaths; and one nemertean. Phylogenetic analysis used the Neighbor-Joining algorithm with Kimura-2-Parameter (K-2-P) distances, with 1000-fold bootstrapping. K-2-P genetic distances between individuals of the same species ranged from 0.0 to 0.2; genetic distances between species ranged widely from 0.1 to 0.7. The mtCOI gene tree showed monophyly (at 100% bootstrap value) for each of the 26 species for which more than one individual was analyzed. Of seven genera for which more than one species was analyzed, four were shown to be monophyletic; three genera were not resolved. At higher taxonomic levels, only the crustacean order Copepoda was resolved, with bootstrap value of 83%. The mtCOI barcodes accurately discriminated and identified known species of 10 taxonomic groups of Arctic Ocean holozooplankton. A comprehensive DNA barcode database for the estimated 300 described species of Arctic holozooplankton will allow rapid assessment of species diversity and distribution in this climate-vulnerable ocean ecosystem.

Estimation of Volume and Freshwater Flux from the Arctic Ocean using SMAP and NCEP CFSv2

NASA Astrophysics Data System (ADS)

Bulusu, S.

2017-12-01

Spatial and temporal monitoring of sea surface salinity (SSS) plays an important role globally and especially over the Arctic Ocean. The Arctic ice melt has led to an influx of freshwater into the Arctic environment, a process that can be observed in SSS. The recently launched NASA's Soil Moisture Active Passive (SMAP) mission is primarily designed for the global monitoring of soil moisture using L- band (1.4GHz) frequency. SMAP also has the capability of measuring SSS and can thus extend the NASA's Aquarius salinity mission (ended June 7, 2015), salinity data record with improved temporal/spatial sampling. In this research an attempt is made to investigate the retrievability of SSS over the Arctic from SMAP satellite. The objectives of this study are to verify the use of SMAP sea surface salinity (and freshwater) variability in the Arctic Ocean and the extent to estimate freshwater, salt and volume flux from the Arctic Ocean. Along with SMAP data we will use NASA's Ice, Cloud,and land Elevation Satellites (ICESat and ICESat-2), and ESA's CryoSat-2, and NASA's Gravity Recovery and Climate Experiment (GRACE) satellites data to estimate ice melt in the Arctic. The preliminary results from SMAP compared well with the NCEP Climate Forecast System version 2 (CFSv2) salinity data in this region capturing patterns fairly well over the Arctic.

The oceanic biological pump modulates the atmospheric transport of persistent organic pollutants to the Arctic.

PubMed

Galbán-Malagón, Cristóbal; Berrojalbiz, Naiara; Ojeda, María-José; Dachs, Jordi

2012-05-29

Semivolatile persistent organic pollutants have the potential to reach remote environments, such as the Arctic Ocean, through atmospheric transport and deposition. Here we show that this transport of polychlorinated biphenyls to the Arctic Ocean is strongly retarded by the oceanic biological pump. A simultaneous sampling of atmospheric, seawater and plankton samples was performed in July 2007 in the Greenland Current and Atlantic sector of the Arctic Ocean. The atmospheric concentrations declined during atmospheric transport over the Greenland Current with estimated half-lives of 1-4 days. These short half-lives can be explained by the high air-to-water net diffusive flux, which is similar in magnitude to the estimated settling fluxes in the water column. Therefore, the decrease of atmospheric concentrations is due to sequestration of atmospheric polychlorinated biphenyls by enhanced air-water diffusive fluxes driven by phytoplankton uptake and organic carbon settling fluxes (biological pump).

The Oliktok Point Arctic Research Facility (OPARF)

NASA Astrophysics Data System (ADS)

Zak, B. D.; Ivey, M.

2011-12-01

For the past year, the US Department of Energy, through Sandia National Laboratories, has operated a Designated User Facility at Oliktok Point Alaska, on the Arctic Ocean coast near the western end of the Prudhoe Bay oil fields. The primary purpose of this user facility is to accommodate and support manned and unmanned airborne measurement platforms over the Arctic Ocean and adjacent coastline as the arctic sea ice recedes. The speed at which the sea ice is receding exceeds model-projected speeds considerably for reasons that are not fully understood. The ultimate objective is to incorporate improved understanding of the radiative and other processes impacting sea ice recession into the relevant climate models. OPARF is based at a USAF Long Range Radar Station, an old Distant Early Warning (DEW) radar station built during the height of the Cold War, but continuing to be operated to track air traffic over the pole. The USAF has graciously granted Sandia and DOE use of selected facilities at Oliktok on a non-interference basis. DOE also maintains FAA-granted Restricted Airspace over Oliktok Point and adjacent ocean. In addition, DOE has also requested that the FAA establish a Warning Area over international waters 30 miles wide and 700 miles long stretching from near Oliktok towards the North Pole. That request is currently being processed by the FAA, with the public comment period now closed. This paper will update OPARF developments for potential users of the Oliktok user facility and other interested researchers.

Arctic Ocean outflow and glacier-ocean interactions modify water over the Wandel Sea shelf (northeastern Greenland)

NASA Astrophysics Data System (ADS)

Dmitrenko, Igor A.; Kirillov, Sergey A.; Rudels, Bert; Babb, David G.; Toudal Pedersen, Leif; Rysgaard, Søren; Kristoffersen, Yngve; Barber, David G.

2017-12-01

The first-ever conductivity-temperature-depth (CTD) observations on the Wandel Sea shelf in northeastern Greenland were collected in April-May 2015. They were complemented by CTDs taken along the continental slope during the Norwegian FRAM 2014-2015 drift. The CTD profiles are used to reveal the origin of water masses and interactions with ambient water from the continental slope and the tidewater glacier outlet. The subsurface water is associated with the Pacific water outflow from the Arctic Ocean. The underlying halocline separates the Pacific water from a deeper layer of polar water that has interacted with the warm Atlantic water outflow through the Fram Strait, recorded below 140 m. Over the outer shelf, the halocline shows numerous cold density-compensated intrusions indicating lateral interaction with an ambient polar water mass across the continental slope. At the front of the tidewater glacier outlet, colder and turbid water intrusions were observed at the base of the halocline. On the temperature-salinity plots these stations indicate a mixing line that is different from the ambient water and seems to be conditioned by the ocean-glacier interaction. Our observations of Pacific water are set within the context of upstream observations in the Beaufort Sea and downstream observations from the Northeast Water Polynya, and clearly show the modification of Pacific water during its advection across the Arctic Ocean. Moreover, ambient water over the Wandel Sea slope shows different thermohaline structures indicating the different origin and pathways of the on-shore and off-shore branches of the Arctic Ocean outflow through the western Fram Strait.

Processes of multibathyal aragonite undersaturation in the Arctic Ocean

USGS Publications Warehouse

Wynn, J.G.; Robbins, L.L.; Anderson, L.G.

2016-01-01

During 3 years of study (2010–2012), the western Arctic Ocean was found to have unique aragonite saturation profiles with up to three distinct aragonite undersaturation zones. This complexity is produced as inflow of Atlantic-derived and Pacific-derived water masses mix with Arctic-derived waters, which are further modified by physiochemical and biological processes. The shallowest aragonite undersaturation zone, from the surface to ∼30 m depth is characterized by relatively low alkalinity and other dissolved ions. Besides local influence of biological processes on aragonite undersaturation of shallow coastal waters, the nature of this zone is consistent with dilution by sea-ice melt and invasion of anthropogenic CO2 from the atmosphere. A second undersaturated zone at ∼90–220 m depth (salinity ∼31.8–35.4) occurs within the Arctic Halocline and is characterized by elevated pCO2 and nutrients. The nature of this horizon is consistent with remineralization of organic matter on shallow continental shelves bordering the Canada Basin and the input of the nutrients and CO2 entrained by currents from the Pacific Inlet. Finally, the deepest aragonite undersaturation zone is at greater than 2000 m depth and is controlled by similar processes as deep aragonite saturation horizons in the Atlantic and Pacific Oceans. The comparatively shallow depth of this deepest aragonite saturation horizon in the Arctic is maintained by relatively low temperatures, and stable chemical composition. Understanding the mechanisms controlling the distribution of these aragonite undersaturation zones, and the time scales over which they operate will be crucial to refine predictive models.

Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean

USGS Publications Warehouse

Polyak, L.; Bischof, J.; Ortiz, J.D.; Darby, D.A.; Channell, J.E.T.; Xuan, C.; Kaufman, D.S.; Lovlie, R.; Schneider, D.A.; Eberl, D.D.; Adler, R.E.; Council, E.A.

2009-01-01

Sediment cores from the western Arctic Ocean obtained on the 2005 HOTRAX and some earlier expeditions have been analyzed to develop a stratigraphic correlation from the Alaskan Chukchi margin to the Northwind and Mendeleev-Alpha ridges. The correlation was primarily based on terrigenous sediment composition that is not affected by diagenetic processes as strongly as the biogenic component, and paleomagnetic inclination records. Chronostratigraphic control was provided by 14C dating and amino-acid racemization ages, as well as correlation to earlier established Arctic Ocean stratigraphies. Distribution of sedimentary units across the western Arctic indicates that sedimentation rates decrease from tens of centimeters per kyr on the Alaskan margin to a few centimeters on the southern ends of Northwind and Mendeleev ridges and just a few millimeters on the ridges in the interior of the Amerasia basin. This sedimentation pattern suggests that Late Quaternary sediment transport and deposition, except for turbidites at the basin bottom, were generally controlled by ice concentration (and thus melt-out rate) and transportation distance from sources, with local variances related to subsurface currents. In the long term, most sediment was probably delivered to the core sites by icebergs during glacial periods, with a significant contribution from sea ice. During glacial maxima very fine-grained sediment was deposited with sedimentation rates greatly reduced away from the margins to a hiatus of several kyr duration as shown for the Last Glacial Maximum. This sedimentary environment was possibly related to a very solid ice cover and reduced melt-out over a large part of the western Arctic Ocean.

Western Arctic Ocean temperature variability during the last 8000 years

USGS Publications Warehouse

Farmer, Jesse R.; Cronin, Thomas M.; De Vernal, Anne; Dwyer, Gary S.; Keigwin, Loyd D.; Thunell, Robert C.

2011-01-01

We reconstructed subsurface (∼200–400 m) ocean temperature and sea-ice cover in the Canada Basin, western Arctic Ocean from foraminiferal δ18O, ostracode Mg/Ca ratios, and dinocyst assemblages from two sediment core records covering the last 8000 years. Results show mean temperature varied from −1 to 0.5°C and −0.5 to 1.5°C at 203 and 369 m water depths, respectively. Centennial-scale warm periods in subsurface temperature records correspond to reductions in summer sea-ice cover inferred from dinocyst assemblages around 6.5 ka, 3.5 ka, 1.8 ka and during the 15th century Common Era. These changes may reflect centennial changes in the temperature and/or strength of inflowing Atlantic Layer water originating in the eastern Arctic Ocean. By comparison, the 0.5 to 0.7°C warm temperature anomaly identified in oceanographic records from the Atlantic Layer of the Canada Basin exceeded reconstructed Atlantic Layer temperatures for the last 1200 years by about 0.5°C.

Distribution of benthic foraminifers (>125 um) in the surface sediments of the Arctic Ocean

USGS Publications Warehouse

Osterman, Lisa E.; Poore, Richard Z.; Foley, Kevin M.

1999-01-01

Census data on benthic foraminifers (>125 ?m) in surface sediment samples from 49 box cores are used to define four depth-controlled biofacies, which will aid in the paleoceanographic reconstruction of the Arctic Ocean. The shelf biofacies contains a mix of shallow-water calcareous and agglutinated species from the continental shelves of the Beaufort and Chukchi Seas and reflects the variable sedimentologic and oceanic conditions of the Arctic shelves. The intermediate-depth calcareous biofacies, found between 500 and 1,100 meters water depth (mwd), contains abundant Cassidulina teretis , presumably indicating the influence of Atlantic-derived water at this depth. In water depths between 1,100 and 3,500 m, a deepwater calcareous biofacies contains abundant Oridorsalis umbonatus . Below 3,500 mwd, the deepwater mixed calcareous/agglutinated biofacies of the Canada, Makarov, and Eurasian Basins reflects a combination of low productivity, dissolution, and sediment transport. Two other benthic foraminiferal species show specific environmental preferences. Fontbotia wuellerstorfi has a depth distribution between 900 and 3,500 mwd, but maximum abundance occurs in the region of the Mendeleyev Ridge. The elevated abundance of F. wuellerstorfi may be related to increased food supply carried by a branch of Atlantic water that crosses the Lomonosov Ridge near the Russian Continental Shelf. Triloculina frigida is recognized to be a species preferring lower slope sediments commonly disturbed by turbidites and bottom currents. INTRODUCTION At present, our understanding of the Arctic Ocean lags behind our understanding of other oceans, and fundamental questions still exist about its role in and response to global climate change. The Arctic Ocean is particularly sensitive to climatic fluctuations because small changes in the amounts of sea-ice cover can alter global albedo and thermohaline circulation (Aagaard and Carmack, 1994). Numerous questions still exist regarding the nature

Arctic Ocean Freshwater: How Robust are Model Simulations

NASA Technical Reports Server (NTRS)

Jahn, A.; Aksenov, Y.; deCuevas, B. A.; deSteur, L.; Haekkinen, S.; Hansen, E.; Herbaut, C.; Houssais, M.-N.; Karcher, M.; Kauker, F.;

Study of Heavy Metals in a Wetland Area Adjacent to a Waste Disposal Site Near Resolute Bay, Canadian High Arctic

NASA Astrophysics Data System (ADS)

Lund, K. E.; Young, K. L.

2004-05-01

Heavy metal contamination in High Arctic systems is of growing concern. Studies have been conducted measuring long range and large point source pollutants, but little research has been done on small point sources such as municipal waste disposal sites. Many Arctic communities are coastal, and local people consume marine wildlife in which concentrations of heavy metals can accumulate. Waste disposal sites are often located in very close proximity to the coastline and leaching of these metals could contaminate food sources on a local scale. Cadmium and lead are the metals focussed on by this study, as the Northern Contaminants Program recognizes them as metals of concern. During the summer of 2003 a study was conducted near Resolute, Nunavut, Canada, to determine the extent of cadmium and lead leaching from a local dumpsite to an adjacent wetland. The ultimate fate of these contaminants is approximately 1 km downslope in the ocean. Transects covering an area of 0.3 km2 were established downslope from the point of disposal and water and soil samples were collected and analyzed for cadmium and lead. Only trace amounts of cadmium and lead were found in the water samples. In the soil samples, low uniform concentrations of cadmium were found that were slightly above background levels, except for adjacent to the point of waste input where higher concentrations were found. Lead soil concentrations were higher than cadmium and varied spatially with soil material and moisture. Overall, excessive amounts of cadmium and lead contamination do not appear to be entering the marine ecosystem. However, soil material and moisture should be considered when establishing waste disposal sites in the far north

Spatial variability of the Arctic Ocean's double-diffusive staircase

NASA Astrophysics Data System (ADS)

Shibley, N. C.; Timmermans, M.-L.; Carpenter, J. R.; Toole, J. M.

2017-02-01

The Arctic Ocean thermohaline stratification frequently exhibits a staircase structure overlying the Atlantic Water Layer that can be attributed to the diffusive form of double-diffusive convection. The staircase consists of multiple layers of O(1) m in thickness separated by sharp interfaces, across which temperature and salinity change abruptly. Through a detailed analysis of Ice-Tethered Profiler measurements from 2004 to 2013, the double-diffusive staircase structure is characterized across the entire Arctic Ocean. We demonstrate how the large-scale Arctic Ocean circulation influences the small-scale staircase properties. These staircase properties (layer thicknesses and temperature and salinity jumps across interfaces) are examined in relation to a bulk vertical density ratio spanning the staircase stratification. We show that the Lomonosov Ridge serves as an approximate boundary between regions of low density ratio (approximately 3-4) on the Eurasian side and higher density ratio (approximately 6-7) on the Canadian side. We find that the Eurasian Basin staircase is characterized by fewer, thinner layers than that in the Canadian Basin, although the margins of all basins are characterized by relatively thin layers and the absence of a well-defined staircase. A double-diffusive 4/3 flux law parametrization is used to estimate vertical heat fluxes in the Canadian Basin to be O(0.1) W m-2. It is shown that the 4/3 flux law may not be an appropriate representation of heat fluxes through the Eurasian Basin staircase. Here molecular heat fluxes are estimated to be between O(0.01) and O(0.1) W m-2. However, many uncertainties remain about the exact nature of these fluxes.

Using an Environmental Intelligence Framework to Evaluate the Impacts of Ocean Acidification in the Arctic

NASA Astrophysics Data System (ADS)

Mathis, J. T.; Baskin, M.; Cross, J.

2016-12-01

The highly productive coastal seas of the Arctic Ocean are located in areas that are projected to experience strong global change, including rapid transitions in temperature and ocean acidification-driven changes in pH and other chemical parameters. Many of the marine organisms that may be most intensely affected by ocean acidification (OA) and other environmental stressors contribute substantially to the commercial fisheries of the Bering Sea and traditional subsistence food supplies across the Arctic. This could represent a looming challenge in many communities as the average prevalence of household food insecurity and very low food security in Alaska are already 12 percent and 4.3 percent, respectively. Here, we evaluate the patterns of dependence on marine resources within Alaska's Arctic that could be negatively impacted by OA and current community characteristics to assess the potential risk to the fishery sector from OA. We used a risk assessment framework to analyze an earth-system global model of ocean chemistry, fisheries harvest data, and demographic information. The analysis showed that regions around Alaska vary in their vulnerability to OA, but that each one will have to deal with possible impacts. Therefore, OA merits consideration in policy planning, as it may represent another challenge to Alaskan communities, some of which are already under acute socio-economic strains. With this in mind, we will present a number of adaptation strategies for communities living throughout Alaska's Arctic that could be applicable to other Arctic regions.

Ocean Dynamics in the Key Regions of North Atlantic-Arctic Exchanges: Evaluation of Global Multi-Resolution FESOM and CMIP-type INMCM Models with Long-Term Observations

NASA Astrophysics Data System (ADS)

Beszczynska-Moeller, A.; Gürses, Ö.; Sidorenko, D.; Goessling, H.; Volodin, E. M.; Gritsun, A.; Iakovlev, N. G.; Andrzejewski, J.

2017-12-01

Enhancing the fidelity of climate models in the Arctic and North Atlantic in order to improve Arctic predictions requires better understanding of the underlying causes of common biases. The main focus of the ERA.Net project NAtMAP (Amending North Atlantic Model Biases to Improve Arctic Predictions) is on the dynamics of the key regions connecting the Arctic and the North Atlantic climate. The study aims not only at increased model realism, but also at a deeper understanding of North Atlantic-Arctic links and their contribution to Arctic predictability. Two complementary approaches employing different global coupled climate models, ECHAM6-FESOM and INMCM4/5, were adopted. The first approach is based on a recent development of climate models with ocean components based on unstructured meshes, allowing to resolve eddies and narrow boundary currents in the most crucial regions while keeping a moderate resolution elsewhere. The multi-resolution sea ice-ocean component of ECHAM6-FESOM allows studying the benefits of very high resolution in key areas of the North Atlantic. An alternative approach to address the North Atlantic and Arctic biases is also tried by tuning the performance of the relevant sub-grid-scale parameterizations in eddy resolving version the CMIP5 climate model INMCM4. Using long-term in situ and satellite observations and available climatologies we attempt to evaluate to what extent a higher resolution, allowing the explicit representation of eddies and narrow boundary currents in the North Atlantic and Nordic Seas, can alleviate the common model errors. The effects of better resolving the Labrador Sea area on reducing the model bias in surface hydrography and improved representation of ocean currents are addressed. Resolving eddy field in the Greenland Sea is assessed in terms of reducing the deep thermocline bias. The impact of increased resolution on the modeled characteristics of Atlantic water transport into the Arctic is examined with a special

Lagrangian Modeling of Arctic Ocean Circulation Pathways: Impact of Advection on Spread of Pollutants

NASA Astrophysics Data System (ADS)

Kelly, S.; Popova, E.; Aksenov, Y.; Marsh, R.; Yool, A.

2018-04-01

Sea-ice-free summers are projected to become a prominent feature of the Arctic environment in the coming decades. From a shipping perspective, this means larger areas of open water in the summer, thinner and less compact ice all year round, and longer operating seasons. Therefore, the possibility for easier navigation along trans-Arctic shipping routes arises. The Northern Sea Route (NSR) is one trans-Arctic route, and it offers a potential 10 day shortcut between Western Europe and the Far East. More ships transiting the NSR means an increased risk of an accident, and associated oil spill, occurring. Previous research suggests that current infrastructure is insufficient for increased shipping. Therefore, should an oil spill occur, the window for a successful clean-up will be short. In the event of a failed recovery, the long-term fate of the unrecovered pollutants must be considered, at least until the next melt season when it could become accessible again. Here we investigate the role of oceanic advection in determining the long-term fate of Arctic pollutants using a high-resolution ocean model along with Lagrangian particle-tracking to simulate the spread of pollutants. The resulting "advective footprints" of pollutants are proposed as an informative metric for analyzing such experiments. We characterize the circulation along different parts of the NSR, defining three main regions in the Eurasian Arctic, and relate the distinctive circulation pathways of each to the long-term fate of spilled oil. We conclude that a detailed understanding of ocean circulation is critical for determining the long-term fate of Arctic pollutants.

Phagotrophy by the picoeukaryotic green alga Micromonas: implications for Arctic Oceans.

PubMed

McKie-Krisberg, Zaid M; Sanders, Robert W

2014-10-01

Photosynthetic picoeukaryotes (PPE) are recognized as major primary producers and contributors to phytoplankton biomass in oceanic and coastal environments. Molecular surveys indicate a large phylogenetic diversity in the picoeukaryotes, with members of the Prymnesiophyceae and Chrysophyseae tending to be more common in open ocean waters and Prasinophyceae dominating coastal and Arctic waters. In addition to their role as primary producers, PPE have been identified in several studies as mixotrophic and major predators of prokaryotes. Mixotrophy, the combination of photosynthesis and phagotrophy in a single organism, is well established for most photosynthetic lineages. However, green algae, including prasinophytes, were widely considered as a purely photosynthetic group. The prasinophyte Micromonas is perhaps the most common picoeukaryote in coastal and Arctic waters and is one of the relatively few cultured representatives of the picoeukaryotes available for physiological investigations. In this study, we demonstrate phagotrophy by a strain of Micromonas (CCMP2099) isolated from Arctic waters and show that environmental factors (light and nutrient concentration) affect ingestion rates in this mixotroph. In addition, we show size-selective feeding with a preference for smaller particles, and determine P vs I (photosynthesis vs irradiance) responses in different nutrient conditions. If other strains have mixotrophic abilities similar to Micromonas CCMP2099, the widespread distribution and frequently high abundances of Micromonas suggest that these green algae may have significant impact on prokaryote populations in several oceanic regimes.

A new high resolution tidal model in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Cancet, Mathilde; Andersen, Ole; Lyard, Florent; Cotton, David; Benveniste, Jérôme

2016-04-01

The Arctic Ocean is a challenging region for tidal modeling, because of its complex and not well-documented bathymetry, together combined with the intermittent presence of sea ice and the fact that the in situ tidal observations are scarce at such high latitudes. As a consequence, the accuracy of the global tidal models decreases by several centimeters in the Polar Regions. It has a large impact on the quality of the satellite altimeter sea surface heights in these regions (ERS1/2, Envisat, CryoSat-2, SARAL/AltiKa and the future Sentinel-3 mission), but also on the end-users' applications that need accurate tidal information. Better knowledge of the tides will improve the quality of the high latitudes altimeter sea surface heights and of all derived products, such as the altimetry-derived geostrophic currents, the mean sea surface and the mean dynamic topography. In addition, accurate tidal models are highly strategic information for ever-growing maritime and industrial activities in this region. NOVELTIS and DTU Space have recently developed a regional, high-resolution tidal atlas in the Arctic Ocean, in the framework of an extension of the CryoSat Plus for Oceans (CP4O) project funded by ESA (STSE program). In particular, this atlas benefits from the assimilation of the most complete satellite altimetry dataset ever used in this region, including the Envisat data up to 82°N and the CryoSat-2 reprocessed data between 82°N and 88°N. The combination of all these satellites gives the best possible coverage of altimetry-derived tidal constituents. Tide gauge data have also been used either for assimilation or validation. This paper presents the methodology followed to develop the model and the performances of this new regional tidal model in the Arctic Ocean.

Arctic circulation regimes

PubMed Central

Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L.

2015-01-01

Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. PMID:26347536

Towards the development of a consensual chronostratigraphy for Arctic Ocean sedimentary records

NASA Astrophysics Data System (ADS)

Hillaire-Marcel, Claude; de Vernal, Anne; Polyak, Leonid; Stein, Rüdiger; Maccali, Jenny; Jacobel, Allison; Cuny, Kristan

2017-04-01

Deciphering Arctic paleoceanograpy and paleoclimate, and linking it to global marine and atmospheric records is much needed for comprehending the Earth's climate history. However, this task is hampered by multiple problems with dating Arctic Ocean sedimentary records related notably to low and highly variable sedimentation rates, scarce and discontinuous biogenic proxies due to low productivity and/or poor preservation, and difficulties correlating regional records to global stacks (e.g., paleomagnetic). Despite recent advances in developing an Arctic Ocean sedimentary stratigraphy, and attempts at setting radiometric benchmark ages of respectively 300 and 150 ka, based on the final decay of 230Th and 231Pa excesses (Thxs, Paxs) (Not et al., 2008), consensual age models are still missing, preventing reliable integration of Arctic records in a global paleoclimatic scheme. Here, we intend to illustrate these issues by comparing consistent Thxs-Paxs chronostratigraphic records from the Mendeleev-Alpha and Lomonosov ridges with the currently used age model based on climatostratigraphic interpretation of sedimentary records (e.g., Polyak et al., 2009; Stein et al., 2010). Data used were collected from the 2005 HOTRAX core MC-11 (northern Mendeleev Ridge) and the 2014 Polarstern core PS87-30 (Lomonosov Ridge). Total collapse depths of Thxs and Paxs are observed by a factor of 3 deeper in core PS87-30 vs core MC-11, indicating average sedimentation rates 3 times higher at the Lomonosov Ridge site. Litho-biostratigraphic markers, such as foraminiferal peaks and manganese-enriched layers, show a similar pattern, with their occurrence 3 times deeper in core PS87-30 than in core MC-11. These very consistent downcore features highlight a gaping difference between the benchmark ages assigned to the total decay of Paxs and Thxs and the current age model based on climatostratigraphic approach involving significantly higher sedimentation rates. This discrepancy begs for its in

Phanerozoic stratigraphy of Northwind Ridge, magnetic anomalies in the Canada Basin, and the geometry and timing of rifting in the Amerasia Basin, Arctic Ocean

USGS Publications Warehouse

Grantz, A.; Clark, D.L.; Phillips, R.L.; Srivastava, S.P.; Blome, C.D.; Gray, L.-B.; Haga, H.; Mamet, B.L.; McIntyre, D.J.; McNeil, D.H.; Mickey, M.B.; Mullen, M.W.; Murchey, B.I.; Ross, C.A.; Stevens, C.H.; Silberling, Norman J.; Wall, J.H.; Willard, D.A.

1998-01-01

Cores from Northwind Ridge, a high-standing continental fragment in the Chukchi borderland of the oceanic Amerasia basin, Arctic Ocean, contain representatives of every Phanerozoic system except the Silurian and Devonian systems. Cambrian and Ordovician shallow-water marine carbonates in Northwind Ridge are similar to basement rocks beneath the Sverdrup basin of the Canadian Arctic Archipelago. Upper Mississippian(?) to Permian shelf carbonate and spicularite and Triassic turbidite and shelf lutite resemble coeval strata in the Sverdrup basin and the western Arctic Alaska basin (Hanna trough). These resemblances indicate that Triassic and older strata in southern Northwind Ridge were attached to both Arctic Canada and Arctic Alaska prior to the rifting that created the Amerasia basin. Late Jurassic marine lutite in Northwind Ridge was structurally isolated from coeval strata in the Sverdrup and Arctic Alaska basins by rift shoulder and grabens, and is interpreted to be a riftogenic deposit. This lutite may be the oldest deposit in the Canada basin. A cape of late Cenomanian or Turonian rhyodacite air-fall ash that lacks terrigenous material shows that Northwind Ridge was structurally isolated from the adjacent continental margins by earliest Late Cretaceous time. Closing Amerasia basin by conjoining seafloor magnetic anomalies beneath the Canada basin or by uniting the pre-Jurassic strata of Northwind Ridge with kindred sections in the Sverdrup basin and Hanna trough yield simular tectonic reconstructions. Together with the orientation and age of rift-marine structures, these data suggest that: 1) prior to opening of the Amerasia basin, both northern Alaska and continental ridges of the Chukchi borderland were part of North America, 2) the extension that created the Amerasia basin formed rift-margin graben beginning in Early Jurassic time and new oceanic crust probably beginning in Late Jurassic or early Neocomian time. Reconstruction of the Amerasia basin on the

Ice-Free Arctic Ocean?

ERIC Educational Resources Information Center

Science Teacher, 2005

2005-01-01

The current warming trends in the Arctic may shove the Arctic system into a seasonally ice-free state not seen for more than one million years, according to a new report. The melting is accelerating, and researchers were unable to identify any natural processes that might slow the deicing of the Arctic. "What really makes the Arctic different…

The freshwater export from the Arctic Ocean and the circulation of liquid freshwater around Greenland - constraints, interactions & consequences

NASA Astrophysics Data System (ADS)

Rudels, Bert

2010-05-01

The freshwater added to the Arctic Ocean is stored as sea ice and as liquid freshwater residing primarily in the upper layers. This allows for simple zero order estimates of the liquid freshwater content and export based on rotationally controlled baroclinic flow. At present the freshwater outflow occurs on both sides of Greenland. In Fram Strait the sea ice export in the East Greenland Current is significantly larger than the liquid freshwater outflow, while the liquid freshwater export dominates in the Canadian Arctic Archipelago. Although the outflow in the upper layer and the freshwater export respond to short periodic wind events and longer periodic atmospheric circulation patterns, the long-term trend is controlled by the net freshwater supply - the freshwater input minus the ice export. As the ice formation and ice export are expected to diminish in a warmer climate the Canadian Arctic Archipelago, comprising several passages, should gradually carry more of the total Arctic Ocean freshwater outflow. However, the channels in the Canadian Arctic Archipelago discharge into the restricted Baffin, which also receives a part of the Fram Strait freshwater export via the West Greenland Current. In a situation with increased glacial melting and freshwater discharge from Greenland the density of the upper layer in Baffin Bay may decrease considerably. This would reduce the sea level difference between the Arctic Ocean and Baffin Bay and thus weaken the outflow through the Canadian Arctic Archipelago, in extreme cases perhaps even reverse the flow. This would shift the main Arctic Ocean liquid freshwater export from The Canadian Arctic Archipelago to Fram Strait. The zero order dynamics of the exchanges through the Canadian Arctic Archipelago and Baffin Bay are described and the possibility for a weakening of the outflow is examined.

Rolling the dice on the ice; New modes for underway data acquisition in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Coakley, B.; Dove, D.

2012-12-01

Exploration of the Arctic Ocean has always depended on the sea ice. It has been a platform supporting drifting ice stations and an obstacle to be over come by force (icebreakers) or finesse (US Navy fast attack submarines). Reduced seasonal sea ice cover has made it possible to work more freely in the peripheral Arctic Ocean, opening relatively unknown regions to scientific exploration and study. In September 2011, the RV Marcus G. Langseth set sail from Dutch Harbor, Alaska bound through Bering Strait for the Arctic Ocean. This was the first Arctic Ocean trip for MGG data acquisition by a US academic research vessel since 1994, when the RV Maurice Ewing collected a 2-D MCS profile across the Bering Shelf, through the Strait and along the Beaufort Shelf, stopping near Barrow, Alaska. RV Langseth arrived on the mid-Chukchi shelf and streamed gear just south of the "Crackerjack" well, drilled by Shell Exploration in the late eighties. The ship sailed north, crossing the "Popcorn" well and then set a course to the NW, setting the baseline for the survey parallel to the Beaufort Shelf edge. Sailing through almost entirely ice-free waters, approximately 5300 km of multi-channel seismic reflection data were acquired on a NW-SE oriented grid, which straddled the transition from Chukchi Shelf to the Chukchi Borderland. It would not have been possible for Langseth, which is not ice reinforced, to acquire these data prior to 2007. The dramatic expansion of late Summer open water in the western Arctic Ocean made it possible to use this ship effectively across a broad swath of the shelf and the periphery of the deep central basin. While the survey region was almost entirely ice free during this cruise, which straddled the ice minimum for 2011, it was not possible to predict this a priori, despite expectations set by the previous five years of ice edge retreat. For this reason, the Canadian Ice Service was engaged to provide interpreted ice imagery, multiple times per day

Arctic Ocean CO2 uptake: an improved multiyear estimate of the air-sea CO2 flux incorporating chlorophyll a concentrations

NASA Astrophysics Data System (ADS)

Yasunaka, Sayaka; Siswanto, Eko; Olsen, Are; Hoppema, Mario; Watanabe, Eiji; Fransson, Agneta; Chierici, Melissa; Murata, Akihiko; Lauvset, Siv K.; Wanninkhof, Rik; Takahashi, Taro; Kosugi, Naohiro; Omar, Abdirahman M.; van Heuven, Steven; Mathis, Jeremy T.

2018-03-01

We estimated monthly air-sea CO2 fluxes in the Arctic Ocean and its adjacent seas north of 60° N from 1997 to 2014. This was done by mapping partial pressure of CO2 in the surface water (pCO2w) using a self-organizing map (SOM) technique incorporating chlorophyll a concentration (Chl a), sea surface temperature, sea surface salinity, sea ice concentration, atmospheric CO2 mixing ratio, and geographical position. We applied new algorithms for extracting Chl a from satellite remote sensing reflectance with close examination of uncertainty of the obtained Chl a values. The overall relationship between pCO2w and Chl a was negative, whereas the relationship varied among seasons and regions. The addition of Chl a as a parameter in the SOM process enabled us to improve the estimate of pCO2w, particularly via better representation of its decline in spring, which resulted from biologically mediated pCO2w reduction. As a result of the inclusion of Chl a, the uncertainty in the CO2 flux estimate was reduced, with a net annual Arctic Ocean CO2 uptake of 180 ± 130 Tg C yr-1. Seasonal to interannual variation in the CO2 influx was also calculated.

Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum

USGS Publications Warehouse

Sluijs, A.; Schouten, S.; Pagani, M.; Woltering, M.; Brinkhuis, H.; Damste, J.S.S.; Dickens, G.R.; Huber, M.; Reichart, G.-J.; Stein, R.; Matthiessen, J.; Lourens, L.J.; Pedentchouk, N.; Backman, J.; Moran, K.; Clemens, S.; Cronin, T.; Eynaud, F.; Gattacceca, J.; Jakobsson, M.; Jordan, R.; Kaminski, M.; King, J.; Koc, N.; Martinez, N.C.; McInroy, D.; Moore, T.C.; O'Regan, M.; Onodera, J.; Palike, H.; Rea, B.; Rio, D.; Sakamoto, T.; Smith, D.C.; St John, K.E.K.; Suto, I.; Suzuki, N.; Takahashi, K.; Watanabe, M. E.; Yamamoto, M.

2006-01-01

The Palaeocene/Eocene thermal maximum, ???55 million years ago, was a brief period of widespread, extreme climatic warming, that was associated with massive atmospheric greenhouse gas input. Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition. We show that sea surface temperatures near the North Pole increased from ???18??C to over 23??C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean's bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations, but the absolute polar temperatures that we derive before, during and after the event are more than 10??C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms-perhaps polar stratospheric clouds or hurricane-induced ocean mixing-to amplify early Palaeogene polar temperatures. ?? 2006 Nature Publishing Group.

[Spectral features analysis of sea ice in the Arctic Ocean].

PubMed

Ke, Chang-qing; Xie, Hong-jie; Lei, Rui-bo; Li, Qun; Sun, Bo

2012-04-01

Sea ice in the Arctic Ocean plays an important role in the global climate change, and its quick change and impact are the scientists' focus all over the world. The spectra of different kinds of sea ice were measured with portable ASD FieldSpec 3 spectrometer during the long-term ice station of the 4th Chinese national Arctic Expedition in 2010, and the spectral features were analyzed systematically. The results indicated that the reflectance of sea ice covered by snow is the highest one, naked sea ice the second, and melted sea ice the lowest. Peak and valley characteristics of spectrum curves of sea ice covered by thick snow, thin snow, wet snow and snow crystal are very significant, and the reflectance basically decreases with the wavelength increasing. The rules of reflectance change with wavelength of natural sea ice, white ice and blue ice are basically same, the reflectance of them is medium, and that of grey ice is far lower than natural sea ice, white ice and blue ice. It is very significant for scientific research to analyze the spectral features of sea ice in the Arctic Ocean and to implement the quantitative remote sensing of sea ice, and to further analyze its response to the global warming.

Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum.

PubMed

Sluijs, Appy; Schouten, Stefan; Pagani, Mark; Woltering, Martijn; Brinkhuis, Henk; Sinninghe Damsté, Jaap S; Dickens, Gerald R; Huber, Matthew; Reichart, Gert-Jan; Stein, Ruediger; Matthiessen, Jens; Lourens, Lucas J; Pedentchouk, Nikolai; Backman, Jan; Moran, Kathryn

2006-06-01

The Palaeocene/Eocene thermal maximum, approximately 55 million years ago, was a brief period of widespread, extreme climatic warming, that was associated with massive atmospheric greenhouse gas input. Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition. We show that sea surface temperatures near the North Pole increased from 18 degrees C to over 23 degrees C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean's bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations, but the absolute polar temperatures that we derive before, during and after the event are more than 10 degrees C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms--perhaps polar stratospheric clouds or hurricane-induced ocean mixing--to amplify early Palaeogene polar temperatures.

Decorrelation scales for Arctic Ocean hydrography - Part I: Amerasian Basin

NASA Astrophysics Data System (ADS)

Sumata, Hiroshi; Kauker, Frank; Karcher, Michael; Rabe, Benjamin; Timmermans, Mary-Louise; Behrendt, Axel; Gerdes, Rüdiger; Schauer, Ursula; Shimada, Koji; Cho, Kyoung-Ho; Kikuchi, Takashi

2018-03-01

Any use of observational data for data assimilation requires adequate information of their representativeness in space and time. This is particularly important for sparse, non-synoptic data, which comprise the bulk of oceanic in situ observations in the Arctic. To quantify spatial and temporal scales of temperature and salinity variations, we estimate the autocorrelation function and associated decorrelation scales for the Amerasian Basin of the Arctic Ocean. For this purpose, we compile historical measurements from 1980 to 2015. Assuming spatial and temporal homogeneity of the decorrelation scale in the basin interior (abyssal plain area), we calculate autocorrelations as a function of spatial distance and temporal lag. The examination of the functional form of autocorrelation in each depth range reveals that the autocorrelation is well described by a Gaussian function in space and time. We derive decorrelation scales of 150-200 km in space and 100-300 days in time. These scales are directly applicable to quantify the representation error, which is essential for use of ocean in situ measurements in data assimilation. We also describe how the estimated autocorrelation function and decorrelation scale should be applied for cost function calculation in a data assimilation system.

An Arctic source for the Great Salinity Anomaly - A simulation of the Arctic ice-ocean system for 1955-1975

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa

1993-01-01

The paper employs a fully prognostic Arctic ice-ocean model to study the interannual variability of sea ice during the period 1955-1975 and to explain the large variability of the ice extent in the Greenland and Iceland seas during the late 1960s. The model is used to test the contention of Aagaard and Carmack (1989) that the Great Salinity Anomaly (GSA) was a consequence of the anomalously large ice export in 1968. The high-latitude ice-ocean circulation changes due to wind field changes are explored. The ice export event of 1968 was the largest in the simulation, being about twice as large as the average and corresponding to 1600 cu km of excess fresh water. The simulations suggest that, besides the above average ice export to the Greenland Sea, there was also fresh water export to support the larger than average ice cover. The model results show the origin of the GSA to be in the Arctic, and support the view that the Arctic may play an active role in climate change.

Quaternary paleoceanography of the deep Arctic Ocean based on quantitative analysis of Ostracoda

USGS Publications Warehouse

Cronin, T. M.; Holtz, T.R.; Whatley, R.C.

1994-01-01

Ostracodes were studied from deep Arctic Ocean cores obtained during the Arctic 91 expedition of the Polarstern to the Nansen, Amundsen and Makarov Basins, the Lomonosov Ridge, Morris Jesup Rise and Yermak Plateau, in order to investigate their distribution in Arctic Ocean deep water (AODW) and apply these data to paleoceanographic reconstruction of bottom water masses during the Quaternary. Analyses of coretop assemblages from Arctic 91 boxcores indicate the following: ostracodes are common at all depths between 1000 and 4500 m, and species distribution is strongly influenced by water mass characteristics and bathymetry; quantitative analyses comparing Eurasian and Canada Basin assemblages indicate that distinct assemblages inhabit regions east and west of the Lomonosov Ridge, a barrier especially important to species living in lower AODW; deep Eurasian Basin assemblages are more similar to those living in Greenland Sea deep water (GSDW) than those in Canada Basin deep water; two upper AODW assemblages were recognized throughout the Arctic Ocean, one living between 1000 and 1500 m, and the other, having high species diversity, at 1500-3000 m. Downcore quantitative analyses of species' abundances and the squared chord distance coefficient of similarity reveals a distinct series of abundance peaks in key indicator taxa interpreted to signify the following late Quaternary deep water history of the Eurasian Basin. During the Last Glacial Maximum (LGM), a GSDW/AODW assemblage, characteristic of cold, well oxygenated deep water > 3000 m today, inhabited the Lomonosov Ridge to depths as shallow as 1000 m, perhaps indicating the influence of GSDW at mid-depths in the central Arctic Ocean. During Termination 1, a period of high organic productivity associated with a strong inflowing warm North Atlantic layer occurred. During the mid-Holocene, several key faunal events indicate a period of warming and/or enhanced flow between the Canada and Eurasian Basins. A long

Determination of a Critical Sea Ice Thickness Threshold for the Central Arctic Ocean

NASA Astrophysics Data System (ADS)

Ford, V.; Frauenfeld, O. W.; Nowotarski, C. J.

2017-12-01

While sea ice extent is readily measurable from satellite observations and can be used to assess the overall survivability of the Arctic sea ice pack, determining the spatial variability of sea ice thickness remains a challenge. Turbulent and conductive heat fluxes are extremely sensitive to ice thickness but are dominated by the sensible heat flux, with energy exchange expected to increase with thinner ice cover. Fluxes over open water are strongest and have the greatest influence on the atmosphere, while fluxes over thick sea ice are minimal as heat conduction from the ocean through thick ice cannot reach the atmosphere. We know that turbulent energy fluxes are strongest over open ocean, but is there a "critical thickness of ice" where fluxes are considered non-negligible? Through polar-optimized Weather Research and Forecasting model simulations, this study assesses how the wintertime Arctic surface boundary layer, via sensible heat flux exchange and surface air temperature, responds to sea ice thinning. The region immediately north of Franz Josef Land is characterized by a thickness gradient where sea ice transitions from the thickest multi-year ice to the very thin marginal ice seas. This provides an ideal location to simulate how the diminishing Arctic sea ice interacts with a warming atmosphere. Scenarios include both fixed sea surface temperature domains for idealized thickness variability, and fixed ice fields to detect changes in the ocean-ice-atmosphere energy exchange. Results indicate that a critical thickness threshold exists below 1 meter. The threshold is between 0.4-1 meters thinner than the critical thickness for melt season survival - the difference between first year and multi-year ice. Turbulent heat fluxes and surface air temperature increase as sea ice thickness transitions from perennial ice to seasonal ice. While models predict a sea ice free Arctic at the end of the warm season in future decades, sea ice will continue to transform

Contrasting glacial/interglacial regimes in the western Arctic Ocean as exemplified by a sedimentary record from the Mendeleev Ridge

USGS Publications Warehouse

Polyak, L.; Curry, W.B.; Darby, D.A.; Bischof, J.; Cronin, T. M.

2004-01-01

Distinct cyclicity in lithology and microfaunal distribution in sediment cores from the Mendeleev Ridge in the western Arctic Ocean (water depths ca. 1. 5 km) reflects contrasting glacial/interglacial sedimentary patterns. We conclude that during major glaciations extremely thick pack ice or ice shelves covered the western Arctic Ocean and its circulation was restricted in comparison with interglacial, modern-type conditions. Glacier collapse events are marked in sediment cores by increased contents of ice-rafted debris, notably by spikes of detrital carbonates and iron oxide grains from the Canadian Arctic Archipelago. Composition of foraminiferal calcite ?? 18O and ??13C also shows strong cyclicity indicating changes in freshwater balance and/or ventilation rates of the Arctic Ocean. Light stable isotopic spikes characterize deglacial events such as the last deglaciation at ca. 12 14C kyr BP. The prolonged period with low ??18O and ??13C values and elevated contents of iron oxide grains from the Canadian Archipelago in the lower part of the Mendeleev Ridge record is interpreted to signify the pooling of freshwater in the Amerasia Basin, possibly in relation to an extended glaciation in arctic North America. Unique benthic foraminiferal events provide a means for an independent stratigraphic correlation of sedimentary records from the Mendeleev Ridge and other mid-depth locations throughout the Arctic Ocean such as the Northwind and Lomonosov Ridges. This correlation demonstrates the disparity of existing age models and underscores the need to establish a definitive chronostratigraphy for Arctic Ocean sediments. ?? 2003 Elsevier B.V. All rights reserved.

Tsunami in the Arctic

NASA Astrophysics Data System (ADS)

Kulikov, Evgueni; Medvedev, Igor; Ivaschenko, Alexey

2017-04-01

The severity of the climate and sparsely populated coastal regions are the reason why the Russian part of the Arctic Ocean belongs to the least studied areas of the World Ocean. In the same time intensive economic development of the Arctic region, specifically oil and gas industry, require studies of potential thread natural disasters that can cause environmental and technical damage of the coastal and maritime infrastructure of energy industry complex (FEC). Despite the fact that the seismic activity in the Arctic can be attributed to a moderate level, we cannot exclude the occurrence of destructive tsunami waves, directly threatening the FEC. According to the IAEA requirements, in the construction of nuclear power plants it is necessary to take into account the impact of all natural disasters with frequency more than 10-5 per year. Planned accommodation in the polar regions of the Russian floating nuclear power plants certainly requires an adequate risk assessment of the tsunami hazard in the areas of their location. Develop the concept of tsunami hazard assessment would be based on the numerical simulation of different scenarios in which reproduced the hypothetical seismic sources and generated tsunamis. The analysis of available geological, geophysical and seismological data for the period of instrumental observations (1918-2015) shows that the highest earthquake potential within the Arctic region is associated with the underwater Mid-Arctic zone of ocean bottom spreading (interplate boundary between Eurasia and North American plates) as well as with some areas of continental slope within the marginal seas. For the Arctic coast of Russia and the adjacent shelf area, the greatest tsunami danger of seismotectonic origin comes from the earthquakes occurring in the underwater Gakkel Ridge zone, the north-eastern part of the Mid-Arctic zone. In this area, one may expect earthquakes of magnitude Mw ˜ 6.5-7.0 at a rate of 10-2 per year and of magnitude Mw ˜ 7.5 at a

Optical Characterisation of Suspended Particles in the Mackenzie River Plume (Canadian Arctic Ocean) and Implications for Ocean Colour Remote Sensing

NASA Technical Reports Server (NTRS)

Doxaran, D.; Ehn, J.; Belanger, S.; Matsuoka, A.; Hooker, S.; Babin, M.

2012-01-01

Climate change significantly impacts Arctic shelf regions in terms of air temperature, ultraviolet radiation, melting of sea ice, precipitation, thawing of permafrost and coastal erosion. Direct consequences have been observed on the increasing Arctic river flow and a large amount of organic carbon sequestered in soils at high latitudes since the last glacial maximum can be expected to be delivered to the Arctic Ocean during the coming decade. Monitoring the fluxes and fate of this terrigenous organic carbon is problematic in such sparsely populated regions unless remote sensing techniques can be developed and proved to be operational. The main objective of this study is to develop an ocean colour algorithm to operationally monitor dynamics of suspended particulate matter (SPM) on the Mackenzie River continental shelf (Canadian Arctic Ocean) using satellite imagery. The water optical properties are documented across the study area and related to concentrations of SPM and particulate organic carbon (POC). Robust SPM and POC : SPM proxies are identified, such as the light backscattering and attenuation coefficients, and relationships are established between these optical and biogeochemical parameters. Following a semi-analytical approach, a regional SPM quantification relationship is obtained for the inversion of the water reflectance signal into SPM concentration. This relationship is reproduced based on independent field optical measurements. It is successfully applied to a selection of MODIS satellite data which allow estimating fluxes at the river mouth and monitoring the extension and dynamics of the Mackenzie River surface plume in 2009, 2010 and 2011. Good agreement is obtained with field observations representative of the whole water column in the river delta zone where terrigenous SPM is mainly constrained (out of short periods of maximum river outflow). Most of the seaward export of SPM is observed to occur within the west side of the river mouth. Future

Kaltag fault, northern Yukon, Canada: Constraints on evolution of Arctic Alaska

NASA Astrophysics Data System (ADS)

Lane, Larry S.

1992-07-01

The Kaltag fault has been linked to several strike-slip models of evolution of the western Arctic Ocean. Hundreds of kilometres of Cretaceous-Tertiary displacement have been hypothesized in models that emplace Arctic Alaska into its present position by either left- or right-lateral strike slip. However, regional-scale displacement is precluded by new potential-field data. Postulated transform emplacement of Arctic Alaska cannot be accommodated by motion on the Kaltag fault or adjacent structures. The Kaltag fault of the northern Yukon is an eastward extrapolation of its namesake in west-central Alaska; however, a connection cannot be demonstrated. Cretaceous-Tertiary displacement on the Alaskan Kaltag fault is probably accommodated elsewhere.

Moderate-resolution sea surface temperature data for the Arctic Ocean Ecoregions

EPA Science Inventory

Sea surface temperature (SST) is an important environmental characteristic in determining the suitability and sustainability of habitats for marine organisms. Of particular interest is the fate of the Arctic Ocean, which provides critical habitat to commercially important fish (M...

Monocarboxylic and dicarboxylic acids over oceans from the East China Sea to the Arctic Ocean: Roles of ocean emissions, continental input and secondary formation.

PubMed

Hu, Qihou; Xie, Zhouqing; Wang, Xinming; Kang, Hui; Zhang, Yuqing; Ding, Xiang; Zhang, Pengfei

2018-05-30

Organic acids are major components in marine organic aerosols. Many studies on the occurrence, sources and sinks of organic acids over oceans in the low and middle latitudes have been conducted. However, the understanding of relative contributions of specific sources to organic acids over oceans, especially in the high latitudes, is still inadequate. This study measured organic acids, including C 14:0 - C 32:0 saturated monocarboxylic acids (MCAs), C 16:1 , C 18:1 and C 18:2 unsaturated MCAs, and di-C 4 - di-C 10 dicarboxylic acids (DCAs), in the marine boundary layer from the East China Sea to the Arctic Ocean during the 3rd Chinese Arctic Research Expedition (CHINARE 08). The average concentrations were 18 ± 16 ng/m 3 and 11 ± 5.4 ng/m 3 for ΣMCA and ΣDCA, respectively. The levels of saturated MCAs were much higher than those of unsaturated DCAs, with peaks at C 16:0 , C 18:0 and C 14:0 . DCAs peaked at di-C 4 , followed by di-C 9 and di-C 8 . Concentrations of MCAs and DCAs generally decreased with increasing latitudes. Sources of MCAs and DCAs were further investigated using principal component analysis with a multiple linear regression (PCA-MLR) model. Overall, carboxylic acids originated from ocean emissions, continental input (including biomass burning, anthropogenic emissions and terrestrial plant emissions), and secondary formation. All the five sources contributed to MCAs with ocean emissions as the predominant source (48%), followed by biomass burning (20%). In contrast, only 3 sources (i.e., secondary formation (50%), anthropogenic emissions (41%) and biomass burning (9%)) contributed to DCAs. Furthermore, the sources varied with regions. Over the Arctic Ocean, only secondary formation and anthropogenic emissions contributed to MCAs and DCAs. Copyright © 2018 Elsevier B.V. All rights reserved.

Anthropogenic radioactivity in the Arctic Ocean--review of the results from the joint German project.

PubMed

Nies, H; Harms, I H; Karcher, M J; Dethleff, D; Bahe, C

1999-09-30

The paper presents the results of the joint project carried out in Germany in order to assess the consequences in the marine environment from the dumping of nuclear wastes in the Kara and Barents Seas. The project consisted of experimental work on measurements of radionuclides in samples from the Arctic marine environment and numerical modelling of the potential pathways and dispersion of contaminants in the Arctic Ocean. Water and sediment samples were collected for determination of radionuclide such as 137Cs, 90Sr, 239 + 240Pu, 238Pu, and 241Am and various organic micropollutants. In addition, a few water and numerous surface sediment samples collected in the Kara Sea and from the Kola peninsula were taken by Russian colleagues and analysed for artificial radionuclide by the BSH laboratory. The role of transport by sea ice from the Kara Sea into the Arctic Ocean was assessed by a small subgroup at GEOMAR. This transport process might be considered as a rapid contribution due to entrainment of contaminated sediments into sea ice, following export from the Kara Sea into the transpolar ice drift and subsequent release in the Atlantic Ocean in the area of the East Greenland Current. Numerical modelling of dispersion of pollutants from the Kara and Barents Seas was carried out both on a local scale for the Barents and Kara Seas and for long range dispersion into the Arctic and Atlantic Oceans. Three-dimensional baroclinic circulation models were applied to trace the transport of pollutants. Experimental results were used to validate the model results such as the discharges from the nuclear reprocessing plant at Sellafield and subsequent contamination of the North Sea up the Arctic Seas.

Assessing the potential and side effects of ocean albedo modification in the Arctic

NASA Astrophysics Data System (ADS)

Mengis, N.; Oschlies, A.; Keller, D. P.; Martin, T.

2015-12-01

The ice albedo feedbacks in the Arctic are a key factor of the positive feedback mechanisms, which amplify climate change in the high northern latitudes. This study assesses the potential and side effects of an idealised Arctic ocean albedo modification (AOAM) experiment under varying emissions scenarios. A first finding is the fact that the decreasing trend in the Arctic summer sea ice extent could only be offset rather than reversed by the implementation of AOAM under increasing atmospheric CO2 emissions. What becomes evident in this study is that the Earth system regulates its internal heat budgets. Therefore a local cooling at the high northern latitudes causes compensatory heat fluxes in the atmosphere and the ocean. Meaning that firstly, the effectiveness of local scale climate intervention will, in the long term, be lowered by these compensatory fluxes and secondly that there are consequences, such as the subsurface warming signal found in this study, which are unexpected and unintended.

Bridging a possible gap of GRACE observations in the Arctic Ocean using existing GRACE data and in situ bottom pressure sensors

NASA Astrophysics Data System (ADS)

Peralta Ferriz, C.; Morison, J.

2014-12-01

Since 2003, the Gravity Recovery and Climate Experiment (GRACE) satellite system has provided the means of investigating month-to-month to inter-annual variability of, among many other things, Arctic Ocean circulation over the entire Arctic Basin. Such a comprehensive picture could not have been achieved with the limited in situ pressure observations available. Results from the first 10 years of ocean bottom pressure measurements from GRACE in the Arctic Ocean reveal distinct patterns of ocean variability that are strongly associated with changes in large-scale atmospheric circulation (Peralta-Ferriz et al., 2014): the leading mode of variability being a wintertime basin-coherent mass change driven by winds in the Nordic Seas; the second mode of variability corresponding to a mass signal coherent along the Siberian shelves, and driven by the Arctic Oscillation; and the third mode being a see-saw between western and eastern Arctic shelves, also driven by the large-scale wind patterns. In order to understand Arctic Ocean changes, it is fundamental to continue to track ocean bottom pressure. Our concern is what to do if the present GRACE system, which is already well beyond its design lifetime, should fail before its follow-on is launched, currently estimated to be in 2017. In this work, we regress time series of pressure from the existing and potential Arctic Ocean bottom pressure recorder locations against the fundamental modes of bottom pressure variation. Our aim is to determine the optimum combination of in situ measurements to represent the broader scale variability now observed by GRACE. With this understanding, we can be better prepared to use in situ observations to at least partially cover a possible gap in GRACE coverage. Reference:Peralta-Ferriz, Cecilia, James H. Morison, John M. Wallace, Jennifer A. Bonin, Jinlun Zhang, 2014: Arctic Ocean Circulation Patterns Revealed by GRACE. J. Climate, 27, 1445-1468. doi: http://dx.doi.org/10.1175/JCLI-D-13-00013.1

Mooring-based long-term observation of oceanographic condition in the Chukchi Ses and Canada Basin of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Kikuchi, Takashi; Itoh, Motoyo; Nishino, Shigeto; Watanabe, Eiji

2015-04-01

Changes of the Arctic Ocean environment are well known as one of the most remarkable evidences of global warming, attracting social and public attentions as well as scientists'. However, to illustrate on-going changes and predict future condition of the Arctic marine environment, we still do not have enough knowledge of Arctic sea ice and marine environment. In particular, lack of observation data in winter, e.g., under sea ice, still remains a key issue for precise understanding of seasonal cycle on oceanographic condition in the Arctic Ocean. Mooring-based observation is one of the most useful methods to collect year-long data in the Arctic Ocean. We have been conducting long-term monitoring using mooring system in the Pacific sector of the Arctic Ocean. Volume, heat, and freshwater fluxes through Barrow Canyon where is a major conduit of Pacific-origin water-masses into the Canada Basin have been observed since 2000. We show from an analysis of the mooring results that volume flux through Barrow Canyon was about 60 % of Bering Strait volume flux. Averaged heat flux ranges from 0.9 to 3.07 TW, which could melt 88,000 to 300,000 km2 of 1m thick ice in the Canada Basin, which likely contributed to sea ice retreat in the Pacific sector of the Arctic Ocean. In winter, we found inter-annual variability in salinity related to coastal polynya activity in the Chukchi Sea. In collaboration with Distributed Biological Observatory (DBO) project, which is one of the tasks of Sustaining Arctic Observing Network (SAON), we also initiated year-long mooring observation in the Hope Valley of the southern Chukchi Sea since 2012. Interestingly, winter oceanographic conditions in the Hope Valley are greatly different between in 2012-2013 and in 2013-2014. We speculate that differences of sea ice freeze-up and coastal polynya activity in the southern Chukchi Sea cause significant difference of winter oceanographic condition. It suggests that recent sea ice reduction in the Pacific

One hundred years of Arctic ice cover variations as simulated by a one-dimensional, ice-ocean model

NASA Astrophysics Data System (ADS)

Hakkinen, S.; Mellor, G. L.

1990-09-01

A one-dimensional ice-ocean model consisting of a second moment, turbulent closure, mixed layer model and a three-layer snow-ice model has been applied to the simulation of Arctic ice mass and mixed layer properties. The results for the climatological seasonal cycle are discussed first and include the salt and heat balance in the upper ocean. The coupled model is then applied to the period 1880-1985, using the surface air temperature fluctuations from Hansen et al. (1983) and from Wigley et al. (1981). The analysis of the simulated large variations of the Arctic ice mass during this period (with similar changes in the mixed layer salinity) shows that the variability in the summer melt determines to a high degree the variability in the average ice thickness. The annual oceanic heat flux from the deep ocean and the maximum freezing rate and associated nearly constant minimum surface salinity flux did not vary significantly interannually. This also implies that the oceanic influence on the Arctic ice mass is minimal for the range of atmospheric variability tested.

Past, Present, and Future: A Science Program for the Arctic Ocean Linking Ancient and Contemporary Observations of Change Through Modeling

NASA Astrophysics Data System (ADS)

Coakley, Bernard; Edmonds, Henrietta N.; Frey, Karen; Gascard, Jean-Claude; Grebmeier, Jacqueline M.; Kassens, Heidemarie; Thiede, Jörn; Wegner, Carolyn

2007-07-01

A follow-up to the 2nd International Conference on Arctic Research Planning, 19-21 November 2007, Potsdam, Germany The Arctic Ocean is the missing piece for any global model. Records of processes at both long and short timescales will be necessary to predict the future evolution of the Arctic Ocean through what appears to be a period of rapid climate change. Ocean monitoring is impoverished without the long-timescale records available from paleoceanography and the boundary conditions that can be obtained from marine geology and geophysics. The past and the present are the key to our ability to predict the future.

Quantifying Methane Emissions from the Arctic Ocean Seabed to the Atmosphere

NASA Astrophysics Data System (ADS)

Platt, Stephen; Pisso, Ignacio; Schmidbauer, Norbert; Hermansen, Ove; Silyakova, Anna; Ferré, Benedicte; Vadakkepuliyambatta, Sunil; Myhre, Gunnar; Mienert, Jürgen; Stohl, Andreas; Myhre, Cathrine Lund

2016-04-01

Large quantities of methane are stored under the seafloor in the shallow waters of the Arctic Ocean. Some of this is in the form of hydrates which may be vulnerable to deomposition due to surface warming. The Methane Emissions from Arctic Ocean to Atmosphere MOCA, (http://moca.nilu.no/) project was established in collaboration with the Centre for Arctic Gas Hydrate, Environment and Climate (CAGE, https://cage.uit.no/). In summer 2014, and summer and autumn 2015 we deployed oceanographic CTD (Conductivity, Temperature, Depth) stations and performed state-of-the-art atmospheric measurements of CH4, CO2, CO, and other meteorological parameters aboard the research vessel Helmer Hanssen west of Prins Karl's Forland, Svalbard. Air samples were collected for isotopic analysis (13C, 2H) and quantification of other hydrocarbons (ethane, propane, etc.). Atmospheric measurements are also available from the nearby Zeppelin Observatory at a mountain close to Ny-Ålesund, Svalbard. We will present data from these measurements that show an upper constraint of the methane flux in measurement area in 2014 too low to influence the annual CH4 budget. This is further supported by top-down constraints (maximum release consistent with observations at the Helmer Hansen and Zeppelin Observatory) determined using FLEXPART foot print sensitivities and the OsloCTM3 model. The low flux estimates despite the presence of active seeps in the area (numerous gas flares were observed using echo sounding) were apparently due to the presence of a stable ocean pycnocline at ~50 m.

Hydrographic changes in the Lincoln Sea in the Arctic Ocean with focus on an upper ocean freshwater anomaly between 2007 and 2010

NASA Astrophysics Data System (ADS)

de Steur, L.; Steele, M.; Hansen, E.; Morison, J.; Polyakov, I.; Olsen, S. M.; Melling, H.; McLaughlin, F. A.; Kwok, R.; Smethie, W. M.; Schlosser, P.

2013-09-01

Hydrographic data from the Arctic Ocean show that freshwater content in the Lincoln Sea, north of Greenland, increased significantly from 2007 to 2010, slightly lagging changes in the eastern and central Arctic. The anomaly was primarily caused by a decrease in the upper ocean salinity. In 2011 upper ocean salinities in the Lincoln Sea returned to values similar to those prior to 2007. Throughout 2008-2010, the freshest surface waters in the western Lincoln Sea show water mass properties similar to fresh Canada Basin waters north of the Canadian Arctic Archipelago. In the northeastern Lincoln Sea fresh surface waters showed a strong link with those observed in the Makarov Basin near the North Pole. The freshening in the Lincoln Sea was associated with a return of a subsurface Pacific Water temperature signal although this was not as strong as observed in the early 1990s. Comparison of repeat stations from the 2000s with the data from the 1990s at 65°W showed an increase of the Atlantic temperature maximum which was associated with the arrival of warmer Atlantic water from the Eurasian Basin. Satellite-derived dynamic ocean topography of winter 2009 showed a ridge extending parallel to the Canadian Archipelago shelf as far as the Lincoln Sea, causing a strong flow toward Nares Strait and likely Fram Strait. The total volume of anomalous freshwater observed in the Lincoln Sea and exported by 2011 was close to 1100±250km3, approximately 13% of the total estimated FW increase in the Arctic in 2008.

A Basin-Wide Examination of the Arctic Ocean's Double-Diffusive Staircase

NASA Astrophysics Data System (ADS)

Shibley, N.; Timmermans, M. L.; Carpenter, J. R.; Toole, J. M.

2016-02-01

The Arctic Ocean thermohaline stratification frequently exhibits a staircase structure above the Atlantic Water Layer consisting of multiple mixed layers of order 1-m in height separated by sharp interfaces. This double-diffusive staircase structure is characterized across the entire Arctic Ocean through a detailed analysis of Ice-Tethered Profiler measurements acquired between 2004 and 2013. Staircase properties (mixed layer thicknesses and temperature-salinity jumps across interfaces) are examined in relation to a bulk vertical density ratio for 50-m spanning the staircase stratification. It is shown that the Lomonosov Ridge serves as an approximate boundary between regions of low density ratio (on the Eurasian side) and higher density ratio (on the Canadian side). We find that the diffusive staircase in the Eurasian Basin is characterized by fewer, thinner mixed layers than that in the Canadian Basin, although the margins of all basins are characterized by relatively thin staircase mixed layers. Using a double-diffusive 4/3 flux law parameterization, the distribution of vertical heat fluxes through the staircase is estimated across the Arctic; it is found that heat fluxes in the Eurasian Basin [O(1) W/m^2] are generally an order of magnitude larger than those in the Canadian Basin [O(0.1) W/m^2].

Influence of the vertical mixing parameterization on the modeling results of the Arctic Ocean hydrology

NASA Astrophysics Data System (ADS)

Iakshina, D. F.; Golubeva, E. N.

2017-11-01

The vertical distribution of the hydrological characteristics in the upper ocean layer is mostly formed under the influence of turbulent and convective mixing, which are not resolved in the system of equations for large-scale ocean. Therefore it is necessary to include additional parameterizations of these processes into the numerical models. In this paper we carry out a comparative analysis of the different vertical mixing parameterizations in simulations of climatic variability of the Arctic water and sea ice circulation. The 3D regional numerical model for the Arctic and North Atlantic developed in the ICMMG SB RAS (Institute of Computational Mathematics and Mathematical Geophysics of the Siberian Branch of the Russian Academy of Science) and package GOTM (General Ocean Turbulence Model1,2, http://www.gotm.net/) were used as the numerical instruments . NCEP/NCAR reanalysis data were used for determination of the surface fluxes related to ice and ocean. The next turbulence closure schemes were used for the vertical mixing parameterizations: 1) Integration scheme based on the Richardson criteria (RI); 2) Second-order scheme TKE with coefficients Canuto-A3 (CANUTO); 3) First-order scheme TKE with coefficients Schumann and Gerz4 (TKE-1); 4) Scheme KPP5 (KPP). In addition we investigated some important characteristics of the Arctic Ocean state including the intensity of Atlantic water inflow, ice cover state and fresh water content in Beaufort Sea.

Quaternary paleoceanography of the central Arctic based on Integrated Ocean Drilling Program Arctic Coring Expedition 302 foraminiferal assemblages

USGS Publications Warehouse

Cronin, T. M.; Smith, S.A.; Eynaud, F.; O'Regan, M.; King, J.

2008-01-01

The Integrated Ocean Drilling Program (IODP) Arctic Coring Expedition (ACEX) Hole 4C from the Lomonosov Ridge in the central Arctic Ocean recovered a continuous 18 in record of Quaternary foraminifera yielding evidence for seasonally ice-free interglacials during the Matuyama, progressive development of large glacials during the mid-Pleistocene transition (MPT) ???1.2-0.9 Ma, and the onset of high-amplitude 100-ka orbital cycles ???500 ka. Foraminiferal preservation in sediments from the Arctic is influenced by primary (sea ice, organic input, and other environmental conditions) and secondary factors (syndepositional, long-term pore water dissolution). Taking these into account, the ACEX 4C record shows distinct maxima in agglutinated foraminiferal abundance corresponding to several interglacials and deglacials between marine isotope stages (MIS) 13-37, and although less precise dating is available for older sediments, these trends appear to continue through the Matuyama. The MPT is characterized by nearly barren intervals during major glacials (MIS 12, 16, and 22-24) and faunal turnover (MIS 12-24). Abundant calcareous planktonic (mainly Neogloboquadrina pachyderma sin.) and benthic foraminifers occur mainly in interglacial intervals during the Brunhes and very rarely in the Matuyama. A distinct faunal transition from calcareous to agglutinated foraminifers 200-300 ka in ACEX 4C is comparable to that found in Arctic sediments from the Lomonosov, Alpha, and Northwind ridges and the Morris Jesup Rise. Down-core disappearance of calcareous taxa is probably related to either reduced sea ice cover prior to the last few 100-ka cycles, pore water dissolution, or both. Copyright 2008 by the American Geophysical Union.

Mooring-based monitoring at the mouth of Barrow Canyon and Hope Valley in the Pacific sector of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Kikuchi, T.; Itoh, M.; Nishino, S.

2016-02-01

Changes of the Arctic Ocean environment are well known as one of the most remarkable evidences of global warming, attracting social and public attentions as well as scientists'. However, to illustrate on-going changes and predict future condition of the Arctic marine environment, we still do not have enough knowledge of Arctic sea ice and marine environment. In particular, lack of observation data in winter, e.g., under sea ice, still remains a key issue for precise understanding of seasonal cycle on oceanographic condition in the Arctic Ocean. Mooring-based observation is one of the most useful methods to collect year-long data in the Arctic Ocean. We have been conducting long-term monitoring using mooring system in the Pacific sector of the Arctic Ocean. Volume, heat, and freshwater fluxes through Barrow Canyon where is a major conduit of Pacific-origin water-masses into the Canada Basin have been observed since 2000. We show from an analysis of the mooring results that volume flux through Barrow Canyon was about 60 % of Bering Strait volume flux. Averaged heat flux ranges from 0.9 to 3.07 TW, which could melt 88,000 to 300,000 km2 of 1m thick ice in the Canada Basin, which likely contributed to sea ice retreat in the Pacific sector of the Arctic Ocean. In winter, we found inter-annual variability in salinity related to coastal polynya activity in the Chukchi Sea and strong upwelling events due to easterly winds. We also initiated year-long mooring observation in the Hope Valley of the southern Chukchi Sea since 2012. Interestingly, winter oceanographic conditions in the Hope Valley are greatly different between in 2012-2013 and in 2013-2014. We speculate that differences of sea ice freeze-up and coastal polynya activity in the southern Chukchi Sea cause significant difference of winter oceanographic condition. It suggests that recent sea ice reduction in the Pacific sector of the Arctic Ocean presumably influences marine environment not only in summer but also

Storm-driven Mixing and Potential Impact on the Arctic Ocean

NASA Technical Reports Server (NTRS)

Yang, Jiayan; Comiso, Josefino; Walsh, David; Krishfield, Richard; Honjo, Susumu; Koblinsky, Chester J. (Technical Monitor)

2001-01-01

Observations of the ocean, atmosphere, and ice made by Ice-Ocean Environmental Buoys (IOEBs) indicate that mixing events reaching the depth of the halocline have occurred in various regions in the Arctic Ocean. Our analysis suggests that these mixing events were mechanically forced by intense storms moving across the buoy sites. In this study, we analyzed these mixing events in the context of storm developments that occurred in the Beaufort Sea and in the general area just north of Fram Strait, two areas with quite different hydrographic structures. The Beaufort Sea is strongly influenced by inflow of Pacific water through Bering Strait, while the area north of Fram Strait is directly affected by the inflow of warm and salty North Atlantic water. Our analyses of the basin-wide evolution of the surface pressure and geostrophic wind fields indicate that the characteristics of the storms could be very different. The buoy-observed mixing occurred only in the spring and winter seasons when the stratification was relatively weak. This indicates the importance of stratification, although the mixing itself was mechanically driven. We also analyze the distribution of storms, both the long-term climatology as well as the patterns for each year in the last two decades. The frequency of storms is also shown to be correlated- (but not strongly) to Arctic Oscillation indices. This study indicates that the formation of new ice that leads to brine rejection is unlikely the mechanism that results in the type of mixing that could overturn the halocline. On the other hand, synoptic-scale storms can force mixing deep enough to the halocline and thermocline layer. Despite a very stable stratification associated with the Arctic halocline, the warm subsurface thermocline water is not always insulated from the mixed layer.

Proxy Constraints on a Warm, Fresh Late Cretaceous Arctic Ocean

NASA Astrophysics Data System (ADS)

Super, J. R.; Li, H.; Pagani, M.; Chin, K.

2015-12-01

The warm Late Cretaceous is thought to have been characterized by open Arctic Ocean temperatures upwards of 15°C (Jenkyns et al., 2004). The high temperatures and low equator-to-pole temperature gradient have proven difficult to reproduce in paleoclimate models, with the role of the atmospheric hydrologic cycle in heat transport being particularly uncertain. Here, sediments, coprolites and fish teeth of Santonian-Campanian age from two high-latitude mixed terrestrial and marine sections on Devon Island in the Canadian High Arctic (Chin et al., 2008) were analyzed using a suite of organic and inorganic proxies to evaluate the temperature and salinity of Arctic seawater. Surface temperature estimates were derived from TEX86 estimates of near-shore, shallow (~100 meters depth) marine sediments (Witkowski et al., 2011) and MBT-CBT estimates from terrestrial intervals and both suggest mean annual temperatures of ~20°C, consistent with previous estimates considering the more southerly location of Devon Island. The oxygen isotope composition of non-diagenetic phosphate from vertebrate coprolites and bony fish teeth were then measured, giving values ranging from +13‰ to +19‰. Assuming the TEX86 temperatures are valid and using the temperature calibration of Puceat 2010, the δ18O values of coprolites imply Arctic Ocean seawater δ18O values between -4‰ and -10‰, implying very fresh conditions. Lastly, the δD of precipitation will be estimated from the hydrogen isotope composition of higher plant leaf waxes (C-25, C-27, C-29 and C-31 n-alkanes) from both terrestrial and marine intervals. Data are used to model the salinity of seawater and the meteoric relationship between δD and δ18O, thereby helping to evaluate the northern high-latitude meteoric water line of the Late Cretaceous.

Poles apart: the "bipolar" pteropod species Limacina helicina is genetically distinct between the Arctic and Antarctic oceans.

PubMed

Hunt, Brian; Strugnell, Jan; Bednarsek, Nina; Linse, Katrin; Nelson, R John; Pakhomov, Evgeny; Seibel, Brad; Steinke, Dirk; Würzberg, Laura

2010-03-23

The shelled pteropod (sea butterfly) Limacina helicina is currently recognised as a species complex comprising two sub-species and at least five "forma". However, at the species level it is considered to be bipolar, occurring in both the Arctic and Antarctic oceans. Due to its aragonite shell and polar distribution L. helicina is particularly vulnerable to ocean acidification. As a key indicator of the acidification process, and a major component of polar ecosystems, L. helicina has become a focus for acidification research. New observations that taxonomic groups may respond quite differently to acidification prompted us to reassess the taxonomic status of this important species. We found a 33.56% (+/-0.09) difference in cytochrome c oxidase subunit I (COI) gene sequences between L. helicina collected from the Arctic and Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms and provides strong evidence for the Arctic and Antarctic populations of L. helicina differing at least at the species level. Recent research has highlighted substantial physiological differences between the poles for another supposedly bipolar pteropod species, Clione limacina. Given the large genetic divergence between Arctic and Antarctic L. helicina populations shown here, similarly large physiological differences may exist between the poles for the L. helicina species group. Therefore, in addition to indicating that L. helicina is in fact not bipolar, our study demonstrates the need for acidification research to take into account the possibility that the L. helicina species group may not respond in the same way to ocean acidification in Arctic and Antarctic ecosystems.

Anomalous Structure of Oceanic Lithosphere in the North Atlantic and Arctic Oceans: A Preliminary Analysis Based on Bathymetry, Gravity and Crustal Structure

NASA Astrophysics Data System (ADS)

Barantsrva, O.

2014-12-01

We present a preliminary analysis of the crustal and upper mantle structure for off-shore regions in the North Atlantic and Arctic oceans. These regions have anomalous oceanic lithosphere: the upper mantle of the North Atlantic ocean is affected by the Iceland plume, while the Arctic ocean has some of the slowest spreading rates. Our specific goal is to constrain the density structure of the upper mantle in order to understand the links between the deep lithosphere dynamics, ocean spreading, ocean floor bathymetry, heat flow and structure of the oceanic lithosphere in the regions where classical models of evolution of the oceanic lithosphere may not be valid. The major focus is on the oceanic lithosphere, but the Arctic shelves with a sufficient data coverage are also included into the analysis. Out major interest is the density structure of the upper mantle, and the analysis is based on the interpretation of GOCE satellite gravity data. To separate gravity anomalies caused by subcrustal anomalous masses, the gravitational effect of water, crust and the deep mantle is removed from the observed gravity field. For bathymetry we use the global NOAA database ETOPO1. The crustal correction to gravity is based on two crustal models: (1) global model CRUST1.0 (Laske, 2013) and, for a comparison, (2) a regional seismic model EUNAseis (Artemieva and Thybo, 2013). The crustal density structure required for the crustal correction is constrained from Vp data. Previous studies have shown that a large range of density values corresponds to any Vp value. To overcome this problem and to reduce uncertainty associated with the velocity-density conversion, we account for regional tectonic variations in the Northern Atlantics as constrained by numerous published seismic profiles and potential-field models across the Norwegian off-shore crust (e.g. Breivik et al., 2005, 2007), and apply different Vp-density conversions for different parts of the region. We present preliminary results

Diazotroph Diversity in the Sea Ice, Melt Ponds, and Surface Waters of the Eurasian Basin of the Central Arctic Ocean.

PubMed

Fernández-Méndez, Mar; Turk-Kubo, Kendra A; Buttigieg, Pier L; Rapp, Josephine Z; Krumpen, Thomas; Zehr, Jonathan P; Boetius, Antje

2016-01-01

The Eurasian basin of the Central Arctic Ocean is nitrogen limited, but little is known about the presence and role of nitrogen-fixing bacteria. Recent studies have indicated the occurrence of diazotrophs in Arctic coastal waters potentially of riverine origin. Here, we investigated the presence of diazotrophs in ice and surface waters of the Central Arctic Ocean in the summer of 2012. We identified diverse communities of putative diazotrophs through targeted analysis of the nifH gene, which encodes the iron protein of the nitrogenase enzyme. We amplified 529 nifH sequences from 26 samples of Arctic melt ponds, sea ice and surface waters. These sequences resolved into 43 clusters at 92% amino acid sequence identity, most of which were non-cyanobacterial phylotypes from sea ice and water samples. One cyanobacterial phylotype related to Nodularia sp. was retrieved from sea ice, suggesting that this important functional group is rare in the Central Arctic Ocean. The diazotrophic community in sea-ice environments appear distinct from other cold-adapted diazotrophic communities, such as those present in the coastal Canadian Arctic, the Arctic tundra and glacial Antarctic lakes. Molecular fingerprinting of nifH and the intergenic spacer region of the rRNA operon revealed differences between the communities from river-influenced Laptev Sea waters and those from ice-related environments pointing toward a marine origin for sea-ice diazotrophs. Our results provide the first record of diazotrophs in the Central Arctic and suggest that microbial nitrogen fixation may occur north of 77°N. To assess the significance of nitrogen fixation for the nitrogen budget of the Arctic Ocean and to identify the active nitrogen fixers, further biogeochemical and molecular biological studies are needed.

Diazotroph Diversity in the Sea Ice, Melt Ponds, and Surface Waters of the Eurasian Basin of the Central Arctic Ocean

PubMed Central

Fernández-Méndez, Mar; Turk-Kubo, Kendra A.; Buttigieg, Pier L.; Rapp, Josephine Z.; Krumpen, Thomas; Zehr, Jonathan P.; Boetius, Antje

2016-01-01

The Eurasian basin of the Central Arctic Ocean is nitrogen limited, but little is known about the presence and role of nitrogen-fixing bacteria. Recent studies have indicated the occurrence of diazotrophs in Arctic coastal waters potentially of riverine origin. Here, we investigated the presence of diazotrophs in ice and surface waters of the Central Arctic Ocean in the summer of 2012. We identified diverse communities of putative diazotrophs through targeted analysis of the nifH gene, which encodes the iron protein of the nitrogenase enzyme. We amplified 529 nifH sequences from 26 samples of Arctic melt ponds, sea ice and surface waters. These sequences resolved into 43 clusters at 92% amino acid sequence identity, most of which were non-cyanobacterial phylotypes from sea ice and water samples. One cyanobacterial phylotype related to Nodularia sp. was retrieved from sea ice, suggesting that this important functional group is rare in the Central Arctic Ocean. The diazotrophic community in sea-ice environments appear distinct from other cold-adapted diazotrophic communities, such as those present in the coastal Canadian Arctic, the Arctic tundra and glacial Antarctic lakes. Molecular fingerprinting of nifH and the intergenic spacer region of the rRNA operon revealed differences between the communities from river-influenced Laptev Sea waters and those from ice-related environments pointing toward a marine origin for sea-ice diazotrophs. Our results provide the first record of diazotrophs in the Central Arctic and suggest that microbial nitrogen fixation may occur north of 77°N. To assess the significance of nitrogen fixation for the nitrogen budget of the Arctic Ocean and to identify the active nitrogen fixers, further biogeochemical and molecular biological studies are needed. PMID:27933047

Assessing climate impacts and risks of ocean albedo modification in the Arctic

NASA Astrophysics Data System (ADS)

Mengis, N.; Martin, T.; Keller, D. P.; Oschlies, A.

2016-05-01

The ice albedo feedback is one of the key factors of accelerated temperature increase in the high northern latitudes under global warming. This study assesses climate impacts and risks of idealized Arctic Ocean albedo modification (AOAM), a proposed climate engineering method, during transient climate change simulations with varying representative concentration pathway (RCP) scenarios. We find no potential for reversing trends in all assessed Arctic climate metrics under increasing atmospheric CO2 concentrations. AOAM only yields an initial offset during the first years after implementation. Nevertheless, sea ice loss can be delayed by 25(60) years in the RCP8.5(RCP4.5) scenario and the delayed thawing of permafrost soils in the AOAM simulations prevents up to 40(32) Pg of carbon from being released by 2100. AOAM initially dampens the decline of the Atlantic Meridional Overturning and delays the onset of open ocean deep convection in the Nordic Seas under the RCP scenarios. Both these processes cause a subsurface warming signal in the AOAM simulations relative to the default RCP simulations with the potential to destabilize Arctic marine gas hydrates. Furthermore, in 2100, the RCP8.5 AOAM simulation diverts more from the 2005-2015 reference state in many climate metrics than the RCP4.5 simulation without AOAM. Considering the demonstrated risks, we conclude that concerning longer time scales, reductions in emissions remain the safest and most effective way to prevent severe changes in the Arctic.

Salinity of the Early and Middle Eocene Arctic Ocean From Oxygen Isotope Analysis of Fish Bone Carbonate

NASA Astrophysics Data System (ADS)

Waddell, L. M.; Moore, T. C.

2006-12-01

Plate tectonic reconstructions indicate that the Arctic was largely isolated from the world ocean during the early and middle Eocene, with exchange limited to shallow, and possibly intermittent, connections to the North Atlantic and Tethys (via the Turgay Strait). Relative isolation, combined with an intensification of the hydrologic cycle under an Eocene greenhouse climate, is suspected to have led to the development of a low- salinity surface water layer in the Arctic that could have affected deep and intermediate convection in the North Atlantic. Sediment cores recently recovered from the Lomonosov Ridge by the IODP 302 Arctic Coring Expedition (ACEX) allow for the first assessment of the salinity of the Arctic Ocean during the early and middle Eocene. Stable isotope analysis performed on the structural carbonate of fish bone apatite from ~30 samples between the ages of ~55 and ~44 myr yielded δ18O values between -6.84‰ and -2.96‰ VPDB, with a mean value of -4.89‰. From the δ18O values we calculate that the Arctic Ocean was probably brackish during most of the early and middle Eocene, with an average salinity of 19 to 24‰. Negative excursions in the δ18O record (<-6‰) indicate three events during which the salinity of the Arctic surface waters was severely lowered: the Paleocene Eocene Thermal Maximum (PETM), the Azolla event at ~49 Ma, and a third previously unidentified event at ~46 Ma. During the PETM, low salinities developed under conditions of increased regional precipitation and runoff associated with extreme high latitude warmth and possible tectonic uplift in the North Atlantic. During the other two low-salinity events, sea level was lowered by ~20-30 m, implying a possible severing of Arctic connections to the world ocean. The most positive δ18O value (-2.96‰) occurs at ~45 Ma, the age of the youngest dropstone discovered in the ACEX sediments, and may therefore correspond to a climatic cooling rather than a high salinity event.

Basin-scale observations of isoprene and monoterpenes in the Arctic and Atlantic Oceans

NASA Astrophysics Data System (ADS)

Carpenter, L.; Hackenberg, S.; Andrews, S.; Minaeian, J.; Chance, R.; Arnold, S.; Spracklen, D. V.; Walker, H.; Brewin, R. J.; Tarran, G.; Tilstone, G.; Small, A.; Bouman, H. A.

2016-12-01

We report surface ocean concentrations, atmospheric mixing ratios and calculated sea-to-air fluxes of isoprene and six monoterpenes (α- and β-pinene, myrcene, Δ 3-carene, ocimene, and limonene) spanning approximately 130 degrees of latitude (80 °N- 50 °S) in the Arctic and Atlantic Oceans. Oceanic isoprene concentrations showed covariance with a number of concurrently monitored biological parameters, and these relationships were dependent on sea surface temperatures. Parameterisations of isoprene seawater concentrations based on linear regression analyses of these relationships perform well for Arctic and Atlantic data. Levels of all monoterpenes were generally low, with oceanic concentrations ranging from below the detection limit of <1 pmol L-1 to 5 pmol L-1 . In air, monoterpene mixing ratios varied from below the detection limit ( 1 pptv) to 5 pptv, after careful filtering for ship-related contamination. Unlike in previous studies, no clear trends or relationships of the monoterpenes with biological data were found. Limonene showed generally the highest levels in water (up to 84 pmol L-1 in the Atlantic Ocean) and air; however this was attributed mostly to shipborne contamination. We calculate global sea-air fluxes of isoprene and monoterpenes based on this data and compare to previous estimates.

Projected Impact of Climate Change on the Water and Salt Budgets of the Arctic Ocean by a Global Climate Model

NASA Technical Reports Server (NTRS)

Miller, James R.; Russell, Gary L.

1996-01-01

The annual flux of freshwater into the Arctic Ocean by the atmosphere and rivers is balanced by the export of sea ice and oceanic freshwater. Two 150-year simulations of a global climate model are used to examine how this balance might change if atmospheric greenhouse gases (GHGs) increase. Relative to the control, the last 50-year period of the GHG experiment indicates that the total inflow of water from the atmosphere and rivers increases by 10% primarily due to an increase in river discharge, the annual sea-ice export decreases by about half, the oceanic liquid water export increases, salinity decreases, sea-ice cover decreases, and the total mass and sea-surface height of the Arctic Ocean increase. The closed, compact, and multi-phased nature of the hydrologic cycle in the Arctic Ocean makes it an ideal test of water budgets that could be included in model intercomparisons.

Moderate-resolution sea surface temperature data and seasonal pattern analysis for the Arctic Ocean ecoregions

USGS Publications Warehouse

Payne, Meredith C.; Reusser, Deborah A.; Lee, Henry

2012-01-01

Sea surface temperature (SST) is an important environmental characteristic in determining the suitability and sustainability of habitats for marine organisms. In particular, the fate of the Arctic Ocean, which provides critical habitat to commercially important fish, is in question. This poses an intriguing problem for future research of Arctic environments - one that will require examination of long-term SST records. This publication describes and provides access to an easy-to-use Arctic SST dataset for ecologists, biogeographers, oceanographers, and other scientists conducting research on habitats and/or processes in the Arctic Ocean. The data cover the Arctic ecoregions as defined by the "Marine Ecoregions of the World" (MEOW) biogeographic schema developed by The Nature Conservancy as well as the region to the north from approximately 46°N to about 88°N (constrained by the season and data coverage). The data span a 29-year period from September 1981 to December 2009. These SST data were derived from Advanced Very High Resolution Radiometer (AVHRR) instrument measurements that had been compiled into monthly means at 4-kilometer grid cell spatial resolution. The processed data files are available in ArcGIS geospatial datasets (raster and point shapefiles) and also are provided in text (.csv) format. All data except the raster files include attributes identifying latitude/longitude coordinates, and realm, province, and ecoregion as defined by the MEOW classification schema. A seasonal analysis of these Arctic ecoregions reveals a wide range of SSTs experienced throughout the Arctic, both over the course of an annual cycle and within each month of that cycle. Sea ice distribution plays a major role in SST regulation in all Arctic ecoregions.

Scientific Discoveries in the Central Arctic Ocean Based on Seafloor Mapping Carried out to Support Article 76 Extended Continental Shelf Claims (Invited)

NASA Astrophysics Data System (ADS)

Jakobsson, M.; Mayer, L. A.; Marcussen, C.

2013-12-01

Despite the last decades of diminishing sea-ice cover in the Arctic Ocean, ship operations are only possible in vast sectors of the central Arctic using the most capable polar-class icebreakers. There are less than a handful of these icebreakers outfitted with modern seafloor mapping equipment. This implies either fierce competition between those having an interest in using these icebreakers for investigations of the shape and properties of Arctic Ocean seafloor or, preferably, collaboration. In this presentation examples will be shown of scientific discoveries based on mapping data collected during Arctic Ocean icebreaker expeditions carried out for the purpose of substantiating claims for an extended continental shelf under United Nations Convention of the Law of the Sea (UNCLOS) Article 76. Scientific results will be presented from the suite of Lomonosov Ridge off Greenland (LOMROG) expeditions (2007, 2009, and 2012), shedding new light on Arctic Ocean oceanography and glacial history. The Swedish icebreaker Oden was used in collaboration between Sweden and Denmark during LOMROG to map and sample portions of the central Arctic Ocean; specifically focused on the Lomonosov Ridge north of Greenland. While the main objective of the Danish participation was seafloor and sub-seabed mapping to substantiate their Article 76 claim, LOMROG also included several scientific components, with scientists from both countries involved. Other examples to be presented are based on data collected using US Coast Guard Cutter Healy, which for several years has carried out mapping in the western Arctic Ocean for the US continental shelf program. All bathymetric data collected with Oden and Healy have been contributed to the International Bathymetric Chart of the Arctic Ocean (IBCAO). This is also the case for bathymetric data collected by Canadian Coast Guard Ship Louis S. St-Laurent for Canada's extended continental shelf claim. Together, the bathymetric data collected during these

Distribution and structure of pranktonic Archaea in the Arctic Ocean using 2008 - 2010 R/V Mirai cruise samples

NASA Astrophysics Data System (ADS)

Amano (Sato), C.; Akiyama, S.; Uchida, M.; Utsumi, M.

2011-12-01

Recent molecular biological techniques indicate that there is widely spreading marine planktonic Archaea in the world's ocean under euphotic zone, and those microbial metabolisms are now recognized the drive forces of the world ocean geochemical cycling. In addition, after the discovery of large amount of marine Archaea, it is pointed out to an accurate calculation of the ocean carbon cycling that the grasp of the Archaea quantitive distribution and their methabolism are indispensable. Remarkably, part of marine Archaea (Crenarchaeota) certainly has carbon fixing ability, thus there is currently great interest in the marine Archaea for getting to understand the carbon cycling. In this study, we evaluated the Archaeal spatial distribution and their biomass in the Pacific sector of the Arctic Ocean, where is the Archaeal quantitative data was less and strongly needed to reveal the marine bacterial carbon cycling due to resent changing the Arctic region such as extensive melting ice. The Arctic Ocean cruise by R/V MIRAI was done from August to October in 2008 - 2010 in the Chukchi Sea, Canada Basin and East Siberian Sea. In these cruises, vertical seawater samples were collected with 12 L Niskin bottles with CTD system at total 30 stations to investigate the distributions of bacterial population density. The Catalyzed Reporter Deposition Fluorescence in situ hybridization (CARD-FISH) technique targeting Crenarchaeal, Euryarchaeal and Eubacterial rRNA was used for identifying and enumerating marine microbial cells under florescent microscope. These cells were counted and measured the size, and calculated the biomass. From the results, in the Pacific sector of the Arctic Ocean, it was determined that the fraction of Archaea was abundant under euphotic zone like as other oceans, and the vertical distribution of planktonic Archaea were obviously different by each sea area. Especially in East Siberian Sea, the fraction of Crenarchaeota was relatively high near bottom

Glimpses of Arctic Ocean shelf-basin interaction from submarine-borne radium sampling

NASA Astrophysics Data System (ADS)

Kadko, David; Aagaard, Knut

2009-01-01

Evidence of shelf-water transfer from temperature, salinity, and 228Ra/ 226Ra sampling from the nuclear submarine USS L. Mendel Rivers SCICEX cruise in October, 2000 demonstrates the heterogeneity of the Arctic Ocean with respect to halocline ventilation. This likely reflects both time-dependent events on the shelves and the variety of dispersal mechanisms within the ocean, including boundary currents and eddies, at least one of which was sampled in this work. Halocline waters at the 132 m sampling depth in the interior Eurasian Basin are generally not well connected to the shelves, consonant with their ventilation within the deep basins, rather than on the shelves. In the western Arctic, steep gradients in 228Ra/ 226Ra ratio and age since shelf contact are consistent with very slow exchange between the Chukchi shelf and the interior Beaufort Gyre. These are the first radium measurements from a nuclear submarine.

Mercury in the atmosphere, snow and melt water ponds in the North Atlantic Ocean during Arctic summer.

PubMed

Aspmo, Katrine; Temme, Christian; Berg, Torunn; Ferrari, Christophe; Gauchard, L Pierre-Alexis; Fain, Xavier; Wibetoe, Grethe

2006-07-01

Atmospheric mercury speciation measurements were performed during a 10 week Arctic summer expedition in the North Atlantic Ocean onboard the German research vessel RV Polarstern between June 15 and August 29, 2004. This expedition covered large areas of the North Atlantic and Arctic Oceans between latitudes 54 degrees N and 85 degrees N and longitudes 16 degrees W and 16 degrees E. Gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and mercury associated with particles (Hg-P) were measured during this study. In addition, total mercury in surface snow and meltwater ponds located on sea ice floes was measured. GEM showed a homogeneous distribution over the open North Atlantic Ocean (median 1.53 +/- 0.12 ng/m3), which is in contrast to the higher concentrations of GEM observed over sea ice (median 1.82 +/- 0.24 ng/m3). It is hypothesized that this results from either (re-) emission of mercury contained in snow and ice surfaces that was previously deposited during atmospheric mercury depletion events (AMDE) in the spring or evasion from the ocean due to increased reduction potential at high latitudes during Arctic summer. Measured concentrations of total mercury in surface snow and meltwater ponds were low (all samples <10 ng/L), indicating that marginal accumulation of mercury occurs in these environmental compartments. Results also reveal low concentrations of RGM and Hg-P without a significant diurnal variability. These results indicate that the production and deposition of these reactive mercury species do not significantly contribute to the atmospheric mercury cycle in the North Atlantic Ocean during the Arctic summer.

Threshold in North Atlantic-Arctic Ocean circulation controlled by the subsidence of the Greenland-Scotland Ridge

PubMed Central

Stärz, Michael; Jokat, Wilfried; Knorr, Gregor; Lohmann, Gerrit

2017-01-01

High latitude ocean gateway changes are thought to play a key role in Cenozoic climate evolution. However, the underlying ocean dynamics are poorly understood. Here we use a fully coupled atmosphere-ocean model to investigate the effect of ocean gateway formation that is associated with the subsidence of the Greenland–Scotland Ridge. We find a threshold in sill depth (∼50 m) that is linked to the influence of wind mixing. Sill depth changes within the wind mixed layer establish lagoonal and estuarine conditions with limited exchange across the sill resulting in brackish or even fresher Arctic conditions. Close to the threshold the ocean regime is highly sensitive to changes in atmospheric CO2 and the associated modulation in the hydrological cycle. For larger sill depths a bi-directional flow regime across the ridge develops, providing a baseline for the final step towards the establishment of a modern prototype North Atlantic-Arctic water exchange. PMID:28580952

The importance of sea ice for exchange of habitat-specific protist communities in the Central Arctic Ocean

NASA Astrophysics Data System (ADS)

Hardge, Kristin; Peeken, Ilka; Neuhaus, Stefan; Lange, Benjamin A.; Stock, Alexandra; Stoeck, Thorsten; Weinisch, Lea; Metfies, Katja

2017-01-01

Sea ice is one of the main features influencing the Arctic marine protist community composition and diversity in sea ice and sea water. We analyzed protist communities within sea ice, melt pond water, under-ice water and deep-chlorophyll maximum water at eight sea ice stations sampled during summer of the 2012 record sea ice minimum year. Using Illumina sequencing, we identified characteristic communities associated with specific habitats and investigated protist exchange between these habitats. The highest abundance and diversity of unique taxa were found in sea ice, particularly in multi-year ice (MYI), highlighting the importance of sea ice as a unique habitat for sea ice protists. Melting of sea ice was associated with increased exchange of communities between sea ice and the underlying water column. In contrast, sea ice formation was associated with increased exchange between all four habitats, suggesting that brine rejection from the ice is an important factor for species redistribution in the Central Arctic. Ubiquitous taxa (e.g. Gymnodinium) that occurred in all habitats still had habitat-preferences. This demonstrates a limited ability to survive in adjacent but different environments. Our results suggest that the continued reduction of sea ice extent, and particularly of MYI, will likely lead to diminished protist exchange and subsequently, could reduce species diversity in all habitats of the Central Arctic Ocean. An important component of the unique sea ice protist community could be endangered because specialized taxa restricted to this habitat may not be able to adapt to rapid environmental changes.

Chronostratigraphy and paleoenvironmental change in the Makarov Basin of the western Arctic Ocean during the last 1 Ma

NASA Astrophysics Data System (ADS)

Park, K.; Nam, S. I.; Khim, B. K.; Kong, G. S.; Schreck, M.; Mackensen, A.; Niessen, F.

2017-12-01

Establishing an accurate chronostratigraphy is essential in reconstructing paleoenvironmental changes in the Arctic Ocean. This requisition, however, has been impeded by the lack of biogenic remnants such as calcareous and siliceous microfossils, as well as alteration of paleomagnetic properties by post-depositional processes. Consequently, foundation of chronostratigraphy in the Arctic Ocean has been mostly relying on stratigraphic correlations. This study examines lithological features and physical properties of sediments of gravity core ARA03B-41GC02 collected in the Makarov Basin and correlates with previously studied cores from the western Arctic Ocean, in order to establish an age model that could eventually facilitate a precise reconstruction of paleoenvironmental changes in the western Arctic Ocean. Age control in the uppermost part was determined by AMS 14C dating of planktonic foraminifera and inter-core correlation was conducted in the upper ca. 3.8 m of the core which corresponded to MIS 15. Age constraints older than MIS 15 were treated using cyclostratigraphic model based on Mn-δ18O stack comparison, assuming that brown and high Mn concentration layers represent generally interglacial or interstadial periods. Based on our result, the core bottom corresponds to MIS 28 with an average sedimentation rate of ca. 0.5 cm/ky. The first appearance of detrital carbonate, planktonic foraminifera, and benthic foraminifera occurred during MIS 16, 11, and 7, respectively. MIS 16 is known as the coldest glacial period when δ18O of the LR04 stack first becomes heavier than 5‰; the occurrence of detrital carbonate likely transported from the Canadian Arctic indicates the initial buildup of the large ice sheets in the North America during this time. Since MIS 11 which is known as the warmest interglacial period during the late Pleistocene in the Northern Hemisphere, the appearance of planktonic foraminifera represents the warmer condition during interglacial

Version 2.0 of the International Bathymetric Chart of the Arctic Ocean: A new Database for Oceanographers and Mapmakers

NASA Astrophysics Data System (ADS)

Jakobsson, M.; Macnab, R.; Edwards, M.; Schenke, H.; Hatzky, J.

2007-12-01

The International Bathymetric Chart of the Arctic Ocean (IBCAO) was first released to the public after its introduction at the American Geophysical Union (AGU) Fall Meeting in 1999 (Jakobsson et al., 2000). This first release consisted of a Digital Bathymetric Model (DBM) on a Polar stereographic projection with grid cell spacing of 2.5 x 2.5 km derived from an accumulated database of all available bathymetric data at the time of compilation. The IBCAO bathymetric database included soundings collected during past and modern expeditions as well as digitized isobaths and depth soundings from published maps. Compared to previous bathymetric maps of the Arctic Ocean, the first released IBCAO compilation was based upon a significantly enhanced database, particularly in the high Arctic. For example, de-classified echo soundings acquired during US and British submarine cruises between 1958 and 1988 were included as well as soundings from icebreaker cruises conducted by Sweden and Germany at the end of the last century. Despite the newly available data in 1999, there were still large areas of the Arctic Ocean where publicly available data were completely absent. Some of these areas had been mapped by Russian agencies, and since these observations were not available to IBCAO, depth contours from the bathymetric contour map published by the Head Department of Navigation and Hydrography (HDNO) (Naryshkin, 1999) were digitized and incorporated in the database. The new IBCAO Version 2.0 comprises the largest update since the first release; moreover, the grid spacing has been decreased to 2 x 2 km. Numerous multibeam data sets that were collected by ice breakers, e.g. USCGC Healy, R/V James Clarke Ross, R/V Polarstern, IB Oden, now form part of the database, as do the swath bathymetric observations acquired during the 1999 SCICEX expedition. The portrayal of the Eastern Arctic Basin is vastly improved due to e.g. the Arctic Mid Ocean Ridge Expedition 2001 (AMORE) and Arctic

On the Flow of Atlantic Water Towards the Arctic Ocean; a Synergy Between Altimetry and Hydrography.

NASA Astrophysics Data System (ADS)

Chafik, L.; Nilsson, J.; Skagseth, O.; Lundberg, P.

2015-12-01

The Arctic climate is strongly influenced by the inflow of warm Atlantic water conveyed by the Norwegian Atlantic Slope Current (NwASC); the main heat conveyor into the Arctic Ocean. Based on sea surface height (SSH) data from altimetry, we develop a dynamical measure of the NwASC transport to diagnose its spatio-temporal variability. This supports a dynamical division of the NwASC into two flow regimes; the Svinøy Branch (SvB) in the Norwegian Sea, and the Fram Strait Branch (FSB) west of Spitsbergen. The SvB transport is well correlated with the SSH and atmospheric variability within the Nordic Seas, factors that also affect the inflow to the Barents Sea. In contrast, the FSB is regulated by regional atmospheric patterns around Svalbard and northern Barents Sea. We further relate anomalous flow events to temperature fluctuations of Atlantic water. A warm anomaly is found to propagate northwards, with a tendency to amplify enroute, after events of strong flow in the Norwegian Sea. A roughly 12-months delayed temperature signal is identified in the FSB. This suggests that hydrographic anomalies both upstream from the North Atlantic, and locally generated in the Norwegian Sea, are important for the oceanic heat and salt transport that eventually enters into the Arctic. We believe that the combination of the flow from altimetry and temperature fluctuations in the Nordic Seas can be used to qualitatively predict warm anomalies towards the Arctic Ocean, which could be a valuable addition to the forecast skill of the statistical Arctic sea-ice models.

ACEX: A First Look at Arctic Ocean Cenozoic History

NASA Astrophysics Data System (ADS)

Moran, K.; Backman, J.

2004-12-01

The first Integrated Ocean Drilling Program mission specificplatform expedition (ACEX - Arctic Coring Expedition) drilled and recovered core from five holes at four sites through Cenozoic sediments draping the crest of the Lomonosov Ridge in the central Arctic Ocean. Coring continued into the underlying Cretaceous sedimentary bedrock. Sites are located only a few nautical miles apart along a single seismic line (AWI-91090), showing an identical and coherent Cenozoic seismostratigraphy. Preliminary results from shipboard investigations of core-catcher-based bio- and lithostratigraphy, pore water analyses and core logger data describe a thick (~160 m) middle Miocene through Pleistocene sequence that shows large amplitude, cyclic variability in the density, magnetic susceptibility and acoustic velocity of the sediments. Sediments are largely carbonate free. Pleistocene sedimentation rates are close to 3 cm/ka, whereas Pliocene sediments are by-and-large missing. A sharp change in physical properties at ~200 m defines the transition into a 200+ m thick Paleogene sequence that is initially dominated by large numbers of dinoflagellate cysts. The early Miocene, Oligocene and late Eocene appear to be largely missing in a hiatus. However, a 32 m thick interval separates the overlying middle Miocene from the underlying middle Eocene and presumably preserves some of the early Neogene and late Paleogene sections. Dinoflagellate cysts, diatoms, ebridians and silicoflagellates are common to abundant in the middle Eocene section, which bottoms in a spectacular layer showing massive occurrences of glochidia and massulae (megaspores) of the freshwater hydropterid fern Azolla (duckweed) at the early/middle Eocene boundary (~306 m), suggesting strongly reduced surface water salinity or perhaps even a brief episode of fresh water conditions at the surface. Biosilica is not present prior to the late early Eocene (~320 m). The (sub-) tropical dinoflagellate species Apectodinium augustum

Arctic geodynamics: Continental shelf and deep ocean geophysics. ERS-1 satellite altimetry: A first look

NASA Technical Reports Server (NTRS)

Anderson, Allen Joel; Sandwell, David T.; Marquart, Gabriele; Scherneck, Hans-Georg

1993-01-01

An overall review of the Arctic Geodynamics project is presented. A composite gravity field model of the region based upon altimetry data from ERS-1, Geosat, and Seasat is made. ERS-1 altimetry covers unique Arctic and Antarctic latitudes above 72 deg. Both areas contain large continental shelf areas, passive margins, as well as recently formed deep ocean areas. Until ERS-1 it was not possible to study these areas with satellite altimetry. Gravity field solutions for the Barents sea, portions of the Arctic ocean, and the Norwegian sea north of Iceland are shown. The gravity anomalies around Svalbard (Spitsbergen) and Bear island are particularly large, indicating large isostatic anomalies which remain from the recent breakup of Greenland from Scandinavian. Recently released gravity data from the Armed Forces Topographic Service of Russia cover a portion of the Barents and Kara seas. A comparison of this data with the ERS-1 produced gravity field is shown.

A synthesis of light absorption properties of the Arctic Ocean: application to semianalytical estimates of dissolved organic carbon concentrations from space

NASA Astrophysics Data System (ADS)

Matsuoka, A.; Babin, M.; Doxaran, D.; Hooker, S. B.; Mitchell, B. G.; Bélanger, S.; Bricaud, A.

2014-06-01

In addition to scattering coefficients, the light absorption coefficients of particulate and dissolved materials are the main factors determining the light propagation of the visible part of the spectrum and are, thus, important for developing ocean color algorithms. While these absorption properties have recently been documented by a few studies for the Arctic Ocean (e.g., Matsuoka et al., 2007, 2011; Ben Mustapha et al., 2012), the data sets used in the literature were sparse and individually insufficient to draw a general view of the basin-wide spatial and temporal variations in absorption. To achieve such a task, we built a large absorption database of the Arctic Ocean by pooling the majority of published data sets and merging new data sets. Our results show that the total nonwater absorption coefficients measured in the eastern Arctic Ocean (EAO; Siberian side) are significantly higher than in the western Arctic Ocean (WAO; North American side). This higher absorption is explained by higher concentration of colored dissolved organic matter (CDOM) in watersheds on the Siberian side, which contains a large amount of dissolved organic carbon (DOC) compared to waters off North America. In contrast, the relationship between the phytoplankton absorption (aϕ(λ)) and chlorophyll a (chl a) concentration in the EAO was not significantly different from that in the WAO. Because our semianalytical CDOM absorption algorithm is based on chl a-specific aϕ(λ) values (Matsuoka et al., 2013), this result indirectly suggests that CDOM absorption can be appropriately derived not only for the WAO but also for the EAO using ocean color data. Based on statistics, derived CDOM absorption values were reasonable compared to in situ measurements. By combining this algorithm with empirical DOC versus CDOM relationships, a semianalytical algorithm for estimating DOC concentrations for river-influenced coastal waters of the Arctic Ocean is presented and applied to satellite

Biased thermohaline exchanges with the Arctic across the Iceland-Faroe Ridge in ocean climate models

NASA Astrophysics Data System (ADS)

Olsen, S. M.; Hansen, B.; Østerhus, S.; Quadfasel, D.; Valdimarsson, H.

2016-04-01

The northern limb of the Atlantic thermohaline circulation and its transport of heat and salt towards the Arctic strongly modulate the climate of the Northern Hemisphere. The presence of warm surface waters prevents ice formation in parts of the Arctic Mediterranean, and ocean heat is directly available for sea-ice melt, while salt transport may be critical for the stability of the exchanges. Through these mechanisms, ocean heat and salt transports play a disproportionally strong role in the climate system, and realistic simulation is a requisite for reliable climate projections. Across the Greenland-Scotland Ridge (GSR) this occurs in three well-defined branches where anomalies in the warm and saline Atlantic inflow across the shallow Iceland-Faroe Ridge (IFR) have been shown to be particularly difficult to simulate in global ocean models. This branch (IF-inflow) carries about 40 % of the total ocean heat transport into the Arctic Mediterranean and is well constrained by observation during the last 2 decades but associated with significant inter-annual fluctuations. The inconsistency between model results and observational data is here explained by the inability of coarse-resolution models to simulate the overflow across the IFR (IF-overflow), which feeds back onto the simulated IF-inflow. In effect, this is reduced in the model to reflect only the net exchange across the IFR. Observational evidence is presented for a substantial and persistent IF-overflow and mechanisms that qualitatively control its intensity. Through this, we explain the main discrepancies between observed and simulated exchange. Our findings rebuild confidence in modelled net exchange across the IFR, but reveal that compensation of model deficiencies here through other exchange branches is not effective. This implies that simulated ocean heat transport to the Arctic is biased low by more than 10 % and associated with a reduced level of variability, while the quality of the simulated salt

Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Ocean.

PubMed

Murton, Julian B; Bateman, Mark D; Dallimore, Scott R; Teller, James T; Yang, Zhirong

2010-04-01

The melting Laurentide Ice Sheet discharged thousands of cubic kilometres of fresh water each year into surrounding oceans, at times suppressing the Atlantic meridional overturning circulation and triggering abrupt climate change. Understanding the physical mechanisms leading to events such as the Younger Dryas cold interval requires identification of the paths and timing of the freshwater discharges. Although Broecker et al. hypothesized in 1989 that an outburst from glacial Lake Agassiz triggered the Younger Dryas, specific evidence has so far proved elusive, leading Broecker to conclude in 2006 that "our inability to identify the path taken by the flood is disconcerting". Here we identify the missing flood path-evident from gravels and a regional erosion surface-running through the Mackenzie River system in the Canadian Arctic Coastal Plain. Our modelling of the isostatically adjusted surface in the upstream Fort McMurray region, and a slight revision of the ice margin at this time, allows Lake Agassiz to spill into the Mackenzie drainage basin. From optically stimulated luminescence dating we have determined the approximate age of this Mackenzie River flood into the Arctic Ocean to be shortly after 13,000 years ago, near the start of the Younger Dryas. We attribute to this flood a boulder terrace near Fort McMurray with calibrated radiocarbon dates of over 11,500 years ago. A large flood into the Arctic Ocean at the start of the Younger Dryas leads us to reject the widespread view that Agassiz overflow at this time was solely eastward into the North Atlantic Ocean.

Effectiveness and Sensitivity of the Arctic Observing Network in a Coupled Ocean-Sea Ice State Estimation Framework

NASA Astrophysics Data System (ADS)

Nguyen, A. T.; Heimbach, P.; Garg, V.; Ocana, V.

2016-12-01

Over the last few decades, various agencies have invested heavily in the development and deployment of Arctic ocean and sea ice observing platforms, especially moorings, profilers, gliders, and satellite-based instruments. These observational assets are heterogeneous in terms of variables sampled and spatio-temporal coverage, which calls for a dynamical synthesis framework of the diverse data streams. Here we introduce an adjoint-based Arctic Subpolar gyre sTate estimate (ASTE), a medium resolution model-data synthesis that leverages all the possible observational assets. Through an established formal state and parameter estimation framework, the ASTE framework produces a 2002-present ocean-sea ice state that can be used to address Arctic System science questions. It is dynamically and kinematically consistent with known equations of motion and consistent with observations. Four key aspects of ASTE will be discussed: (1) How well is ASTE constrained by the existing observations; (2) which data most effectively constrain the system, and what impact on the solution does spatial and temporal coverage have; (3) how much information does one set of observation (e.g. Fram Strait heat transport) carry about a remote, but dynamically linked component (e.g. heat content in the Beaufort Gyre); and (4) how can the framework be used to assess the value of hypothetical observations in constraining poorly observed parts of the Arctic Ocean and the implied mechanisms responsible for the changes occurring in the Arctic. We will discuss the suggested geographic distribution of new observations to maximize the impact on improving our understanding of the general circulation, water mass distribution and hydrographic changes in the Arctic.

Physical and Chemical Properties of Individual Marine Aerosols Collected over the Arctic Ocean

NASA Astrophysics Data System (ADS)

Yoshizue, M.; Taketani, F.; Adachi, K.; Iwamoto, Y.; Mori, T.; Miura, K.

2017-12-01

Atmospheric aerosol particles including black carbon (BC) play an important role in Arctic climate effect through absorbing and scattering solar radiation. However, quantitative understanding of atmospheric aerosol's behavior in Arctic region is limited. In this study, we characterized the mixing states and chemical compositions of marine aerosol particles collected over the Arctic Ocean on the basis of an individual particle analysis using a transmission electron microscope (TEM) and an energy dispersive X-ray spectrometer. Observations and TEM samplings were conducted on-board the R/V Mirai from 22 August to 5 October 2016 in a round trip to the Arctic Ocean from a port of Hachinohe (40.52°N, 141.51°E), Japan. Samplings of atmospheric aerosol particles were carried out on the flying deck (18 m a.s.l.) of R/V Mirai using a low volume cascade impactor with a volumetric flow of 1 L/min. The sampling times ranged from 40 to 70 min. To monitor ambient BC mass concentrations, we also used an online instrument of single particle soot photometer (SP2). In >70°N, we captured relatively high BC mass concentration events on 7 and 16 September 2016 at 71.70°N, 155.10°W and 72.48°N, 155.42°W, respectively. Within clean condition samples on 11 and 14 September 2016, the number fractions of sulfur-rich (S-rich) and carbon-rich (C-rich) particles were, respectively, less than 40% and 15% in the analyzed particles (n=423). On the other hand, in the sample collected at 7 September, the number fractions of S- and C-rich particles were more than 70% and about 5% (n=299), respectively, suggesting that the air mass had been affected by anthropogenic substances. In a sample collected at 16 September, the number fractions of S- and C-rich particles were about 15% and 40% (n=88), respectively. The backward trajectory analyses indicated that the air masses came from Siberian coastal area through the East Siberian Sea, suggesting that the events might be influenced by long

Sedimentary Cover of the Central Arctic

NASA Astrophysics Data System (ADS)

Kireev, Artem; Poselov, Viktor; Butsenko, Viktor; Smirnov, Oleg

2017-04-01

Partial revised Submission of the Russian Federation for establishment of the OLCS (outer limit of the continental shelf) in the Arctic Ocean is made to include in the extended continental shelf of the Russian Federation, in accordance with article 76 of the Convention, the seabed and its subsoil in the central Arctic Ocean which is natural prolongation of the Russian land territory. To submit partial revised Submission in 2016, in 2005 - 2014 the Russian organizations carried out a wide range of geophysical studies, so that today over 23000 km of MCS lines, over hundreds of wide-angle reflection/refraction seismic sonobuoy soundings and 4000 km of deep seismic sounding are accomplished. All of these MCS and seismic soundings data were used to establish the seismic stratigraphy model of the Arctic region. Stratigraphy model of the sedimentary cover was successively determined for the Cenozoic and pre-Cenozoic parts of the section and was based on correlation of the Russian MCS data and seismic data documented by existing boreholes. Interpretation of the Cenozoic part of the sedimentary cover was based on correlation of the Russian MCS data and AWI91090 section calibrated by ACEX-2004 boreholes on the Lomonosov Ridge for Amerasia basin and by correlation of onlap contacts onto oceanic crust with defined magnetic anomalies for Eurasia basin, while interpretation of the Pre-Cenozoic part of the sedimentary cover was based on correlation with MCS and boreholes data from Chukchi sea shelf. Six main unconformities were traced: regional unconformity (RU), Eocene unconformity (EoU) (for Eurasia basin only), post-Campanian unconformity (pCU), Brookian (BU - base of the Lower Brookian unit), Lower Cretaceous (LCU) and Jurassic (JU - top of the Upper Ellesmerian unit). The final step in our research was to estimate the total thickness of the sedimentary cover of the Arctic Ocean and adjacent Eurasian shelf using top of acoustic basement correlation data and bathymetry data

The Open-Ocean Sensible Heat Flux and Its Significance for Arctic Boundary Layer Mixing During Early Fall

NASA Technical Reports Server (NTRS)

Ganeshan, Manisha; Wu, Dongliang

2016-01-01

The increasing ice-free area during late summer has transformed the Arctic to a climate system with more dynamic boundary layer (BL) clouds and seasonal sea ice growth. The open-ocean sensible heat flux, a crucial mechanism of excessive ocean heat loss to the atmosphere during the fall freeze season, is speculated to play an important role in the recently observed cloud cover increase and BL instability. However, lack of observations and understanding of the resilience of the proposed mechanisms, especially in relation to meteorological and interannual variability, has left a poorly constrained BL parameterization scheme in Arctic climate models. In this study, we use multiyear Japanese cruise-ship observations from RV Mirai over the open Arctic Ocean to characterize the surface sensible heat flux (SSHF) during early fall and investigate its contribution to BL turbulence. It is found that mixing by SSHF is favored during episodes of high surface wind speed and is also influenced by the prevailing cloud regime. The deepest BLs and maximum ocean-atmosphere temperature difference are observed during cold air advection (associated with the stratocumulus regime), yet, contrary to previous speculation, the efficiency of sensible heat exchange is low. On the other hand, the SSHF contributes significantly to BL mixing during the uplift (low pressure) followed by the highly stable (stratus) regime. Overall, it can explain 10 of the open ocean BL height variability, whereas cloud-driven (moisture and radiative) mechanisms appear to be the other dominant source of convective turbulence. Nevertheless, there is strong interannual variability in the relationship between the SSHF and the BL height which can be intensified by the changing occurrence of Arctic climate patterns, such as positive surface wind speed anomalies and more frequent conditions of uplift. This study highlights the need for comprehensive BL observations like the RV Mirai for better understanding and

SMOS sea surface salinity maps of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Gabarro, Carolina; Olmedo, Estrella; Turiel, Antonio; Ballabrera-Poy, Joaquim; Martinez, Justino; Portabella, Marcos

2016-04-01

years of SMOS data acquisitions. The second is the modification of the filtering criterion to account for the statistical distributions of SSS at each ocean grid point. This allows retrieving a value of SSS which is less affected by outliers originated from RFI and other effects. We will provide an assessment of the quality of these new SSS products in the Arctic, as well as illustrate the potential of these maps to monitor the main river discharges to the Arctic Ocean. [1] Font, J.; Camps, A.; Borges, A.; Martín-Neira, M.; Boutin, J.; Reul, N.; Kerr, Y.; Hahne, A. & Mecklenburg, S. SMOS: The Challenging Sea Surface Salinity Measurement From Space Proceedings of the IEEE, 2010, 98, 649 -665

Baroclinic stabilization effect of the Atlantic-Arctic water exchange simulated by the eddy-permitting ocean model and global atmosphere-ocean model

NASA Astrophysics Data System (ADS)

Moshonkin, Sergey; Bagno, Alexey; Gritsun, Andrey; Gusev, Anatoly

2017-04-01

Numerical experiments were performed with the global atmosphere-ocean model INMCM5 (for version of the international project CMIP6, resolution for atmosphere is 2°x1.5°, 21 level) and with the three-dimensional, free surface, sigma coordinate eddy-permitting ocean circulation model for Atlantic (from 30°S) - Arctic and Bering sea domain (0.25 degrees resolution, Institute of Numerical Mathematics Ocean Model or INMOM). Spatial resolution of the INMCM5 oceanic component is 0.5°x0.25°. Both models have 40 s-levels in ocean. Previously, the simulations were carried out for INMCM5 to generate climatic system stable state. Then model was run for 180 years. In the experiment with INMOM, CORE-II data for 1948-2009 were used. As the goal for comparing results of two these numerical models, we selected evolution of the density and velocity anomalies in the 0-300m active ocean layer near Fram Strait in the Greenland Sea, where oceanic cyclonic circulation influences Atlantic-Arctic water exchange. Anomalies were count without climatic seasonal cycle for time scales smaller than 30 years. We use Singular Value Decomposition analysis (SVD) for density-velocity anomalies with time lag from minus one to six months. Both models perform identical stable physical result. They reveal that changes of heat and salt transports by West Spitsbergen and East Greenland currents, caused by atmospheric forcing, produce the baroclinic modes of velocity anomalies in 0-300m layer, thereby stabilizing ocean response on the atmospheric forcing, which stimulates keeping water exchange between the North Atlantic and Arctic Ocean at the certain climatological level. The first SVD-mode of density-velocity anomalies is responsible for the cyclonic circulation variability. The second and third SVD-modes stabilize existing ocean circulation by the anticyclonic vorticity generation. The second and third SVD-modes give 35% of the input to the total dispersion of density anomalies and 16-18% of the

Anoxia and high primary production in the Paleogene central Arctic Ocean: First detailed records from Lomonosov Ridge

NASA Astrophysics Data System (ADS)

Stein, Ruediger; Boucsein, Bettina; Meyer, Hanno

2006-09-01

Except for a few discontinuous fragments of the Late Cretaceous/Early Cenozoic climate history and depositional environment, the paleoenvironmental evolution of the pre-Neogene central Arctic Ocean was virtually unknown prior to the IODP Expedition 302 (Arctic Ocean Coring Expedition-ACEX) drilling campaign on Lomonosov Ridge in 2004. Here we present detailed organic carbon (OC) records from the entire ca. 200 m thick Paleogene OC-rich section of the ACEX drill sites. These records indicate euxinic "Black Sea-type" conditions favorable for the preservation of labile aquatic (marine algae-type) OC occur throughout the upper part of the early Eocene and the middle Eocene, explained by salinity stratification due to freshwater discharge. The superimposed short-term ("Milankovitch-type") variability in amount and composition of OC is related to changes in primary production and terrigenous input. Prominent early Eocene events of algae-type OC preservation coincide with global δ13C events such as the PETM and Elmo events. The Elmo δ13C Event has been identified in the Arctic Ocean for the first time.

Poles Apart: The “Bipolar” Pteropod Species Limacina helicina Is Genetically Distinct Between the Arctic and Antarctic Oceans

PubMed Central

Bednarsek, Nina; Linse, Katrin; Nelson, R. John; Pakhomov, Evgeny; Seibel, Brad; Steinke, Dirk; Würzberg, Laura

2010-01-01

The shelled pteropod (sea butterfly) Limacina helicina is currently recognised as a species complex comprising two sub-species and at least five “forma”. However, at the species level it is considered to be bipolar, occurring in both the Arctic and Antarctic oceans. Due to its aragonite shell and polar distribution L. helicina is particularly vulnerable to ocean acidification. As a key indicator of the acidification process, and a major component of polar ecosystems, L. helicina has become a focus for acidification research. New observations that taxonomic groups may respond quite differently to acidification prompted us to reassess the taxonomic status of this important species. We found a 33.56% (±0.09) difference in cytochrome c oxidase subunit I (COI) gene sequences between L. helicina collected from the Arctic and Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms and provides strong evidence for the Arctic and Antarctic populations of L. helicina differing at least at the species level. Recent research has highlighted substantial physiological differences between the poles for another supposedly bipolar pteropod species, Clione limacina. Given the large genetic divergence between Arctic and Antarctic L. helicina populations shown here, similarly large physiological differences may exist between the poles for the L. helicina species group. Therefore, in addition to indicating that L. helicina is in fact not bipolar, our study demonstrates the need for acidification research to take into account the possibility that the L. helicina species group may not respond in the same way to ocean acidification in Arctic and Antarctic ecosystems. PMID:20360985

Land Ice Freshwater Budget of the Arctic and North Atlantic Oceans: 1. Data, Methods, and Results

NASA Astrophysics Data System (ADS)

Bamber, J. L.; Tedstone, A. J.; King, M. D.; Howat, I. M.; Enderlin, E. M.; van den Broeke, M. R.; Noel, B.

2018-03-01

The freshwater budget of the Arctic and sub-polar North Atlantic Oceans has been changing due, primarily, to increased river runoff, declining sea ice and enhanced melting of Arctic land ice. Since the mid-1990s this latter component has experienced a pronounced increase. We use a combination of satellite observations of glacier flow speed and regional climate modeling to reconstruct the land ice freshwater flux from the Greenland ice sheet and Arctic glaciers and ice caps for the period 1958-2016. The cumulative freshwater flux anomaly exceeded 6,300 ± 316 km3 by 2016. This is roughly twice the estimate of a previous analysis that did not include glaciers and ice caps outside of Greenland and which extended only to 2010. From 2010 onward, the total freshwater flux is about 1,300 km3/yr, equivalent to 0.04 Sv, which is roughly 40% of the estimated total runoff to the Arctic for the same time period. Not all of this flux will reach areas of deep convection or Arctic and Sub-Arctic seas. We note, however, that the largest freshwater flux anomalies, grouped by ocean basin, are located in Baffin Bay and Davis Strait. The land ice freshwater flux displays a strong seasonal cycle with summer time values typically around five times larger than the annual mean. This will be important for understanding the impact of these fluxes on fjord circulation, stratification, and the biogeochemistry of, and nutrient delivery to, coastal waters.

What Drives the Variability of the Atlantic Water Circulation in the Arctic Ocean?

NASA Astrophysics Data System (ADS)

Lique, C.; Johnson, H. L.

2016-02-01

The Atlantic Water (AW) layer in the Arctic Basin is isolated from the atmosphere by the overlaying surface layer; yet observations of the AW pan-Arctic boundary current have revealed that the velocities in this layer exhibit significant variations on all timescales. Here, analysis of a global ocean/sea ice model hindcast, complemented by experiments performed with an idealized process model, are used to investigate what controls the variability of AW circulation, with a focus on the role of wind forcing. The AW circulation carries the imprint of wind variations, both remotely over the Nordic and Barents seas where they force variability on the AW inflow to the Arctic Basin, and locally over the Arctic Basin through the forcing of the wind-driven Beaufort gyre, which modulates and transfers the wind variability to the AW layer. Our results further suggest that understanding variability in the large amount of heat contained within the AW layer requires a better understanding of the circulation within both AW and surface layers.

Integrating Research on Global Climate Change and Human Use of the Oceans: a Geospatial Method for Daily Monitoring of Sea Ice and Ship Traffic in the Arctic

NASA Astrophysics Data System (ADS)

Eucker, W.; McGillivary, P. A.

2012-12-01

One apparent consequence of global climate change has been a decrease in the extent and thickness of Arctic sea ice more rapidly than models have predicted, while Arctic ship traffic has likewise increased beyond economic predictions. To ensure representative observations of changing climate conditions and human use of the Arctic Ocean, we concluded a method of tracking daily changes in both sea ice and shipping in the Arctic Ocean was needed. Such a process improves the availability of sea ice data for navigational safety and allows future developments to be monitored for understanding of ice and shipping in relation to policy decisions appropriate to optimize sustainable use of a changing Arctic Ocean. The impetus for this work was the 2009 Arctic Marine Shipping Assessment (AMSA) which provided baseline data on Arctic ship traffic. AMSA was based on responses from circumpolar countries, was manpower intensive, and took years to compile. A more timely method of monitoring human use of the Arctic Ocean was needed. To address this, a method of monitoring sea ice on a scale relevant to ship-navigation (<10km) was developed and implemented in conjunction with arctic ship tracking using S-AIS (Satellite Automatic Identification Systems). S-AIS is internationally required on ships over a certain size, which includes most commercial vessels in the Arctic Ocean. Daily AIS and sea ice observations were chosen for this study. Results of this method of geospatial analysis of the entire arctic are presented for a year long period from April 1, 2010 to March 31, 2011. This confirmed the dominance of European Arctic ship traffic. Arctic shipping is maximal during August and diminishes in September with a minimum in winter, although some shipping continues year-round in perennially ice-free areas. Data are analyzed for the four principal arctic quadrants around the North Pole by season for number and nationality of vessels. The goal of this study was not merely to monitor ship

Arctic sea ice in the global eddy-permitting ocean reanalysis ORAP5

NASA Astrophysics Data System (ADS)

Tietsche, Steffen; Balmaseda, Magdalena A.; Zuo, Hao; Mogensen, Kristian

2017-08-01

We discuss the state of Arctic sea ice in the global eddy-permitting ocean reanalysis Ocean ReAnalysis Pilot 5 (ORAP5). Among other innovations, ORAP5 now assimilates observations of sea ice concentration using a univariate 3DVar-FGAT scheme. We focus on the period 1993-2012 and emphasize the evaluation of model performance with respect to recent observations of sea ice thickness. We find that sea ice concentration in ORAP5 is close to assimilated observations, with root mean square analysis residuals of less than 5 % in most regions. However, larger discrepancies exist for the Labrador Sea and east of Greenland during winter owing to biases in the free-running model. Sea ice thickness is evaluated against three different observational data sets that have sufficient spatial and temporal coverage: ICESat, IceBridge and SMOSIce. Large-scale features like the gradient between the thickest ice in the Canadian Arctic and thinner ice in the Siberian Arctic are simulated well by ORAP5. However, some biases remain. Of special note is the model's tendency to accumulate too thick ice in the Beaufort Gyre. The root mean square error of ORAP5 sea ice thickness with respect to ICESat observations is 1.0 m, which is on par with the well-established PIOMAS model sea ice reconstruction. Interannual variability and trend of sea ice volume in ORAP5 also compare well with PIOMAS and ICESat estimates. We conclude that, notwithstanding a relatively simple sea ice data assimilation scheme, the overall state of Arctic sea ice in ORAP5 is in good agreement with observations and will provide useful initial conditions for predictions.

Circumpolar measurements of speciated mercury, ozone and carbon monoxide in the boundary layer of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Sommar, J.; Andersson, M. E.; Jacobi, H.-W.

2010-06-01

Using the Swedish icebreaker Oden as a platform, continuous measurements of airborne mercury (gaseous elemental mercury (Hg0), divalent gaseous mercury species HgIIX2(g) (acronym RGM) and mercury attached to particles (PHg)) and some long-lived trace gases (carbon monoxide CO and ozone O3) were performed over the North Atlantic and the Arctic Ocean. The measurements were performed for nearly three months (July-September 2005) during the Beringia 2005 expedition (from Göteborg, Sweden via the proper Northwest Passage to the Beringia region Alaska - Chukchi Penninsula - Wrangel Island and in-turn via a north-polar transect to Longyearbyen, Spitsbergen). The Beringia 2005 expedition was the first time that these species have been measured during summer over the Arctic Ocean going from 60° to 90° N. During the North Atlantic transect, concentration levels of Hg0, CO and O3 were measured comparable to typical levels for the ambient mid-hemispheric average. However, a rapid increase of Hg0 in air and surface water was observed when entering the ice-covered waters of the Canadian Arctic archipelago. Large parts of the measured waters were supersaturated with respect to Hg0, reflecting a strong disequilibrium. Heading through the sea ice of the Arctic Ocean, a fraction of the strong Hg0 pulse in the water was transferred with some time-delay into the air samples collected ~20 m above sea level. Several episodes of elevated Hg0 in air were encountered along the sea ice route with higher mean concentration (1.81±0.43 ng m-3) compared to the marine boundary layer over ice-free Arctic oceanic waters (1.55±0.21 ng m-3). In addition, the bulk of the variance in the temporal series of Hg0 concentrations was observed during July. The Oden Hg0 observations compare in this aspect very favourably with those at the coastal station Alert. Atmospheric boundary layer O3 mixing ratios decreased when initially sailing northward. In the Arctic, an O3 minimum around 15-20 ppbV was

The vertical distribution of nutrients and oxygen 18 in the upper Arctic Ocean

NASA Astrophysics Data System (ADS)

BjöRk, GöRan

1990-09-01

The observed vertical nutrient distribution including a maximum at about 100 m depth in the Arctic Ocean is investigated using a one-dimensional time-dependent circulation model together with a simple biological model. The circulation model includes a shelf-forced circulation. This is thought to take place in a box from which the outflow is specified regarding temperature and volume flux at different salinities. It has earlier been shown that the circulation model is able to reproduce the observed mean salinity and temperature stratification in the Arctic Ocean. Before introducing nutrients in the model a test is performed using the conservative tracer δ18 (18O/16O ratio) as one extra state variable in order to verify the circulation model. It is shown that the field measurements can be simulated. The result is, however, rather sensitive to the tracer concentration in the Bering Strait inflow. The nutrients nitrate, phosphate, and silicate are then treated by coupling a simple biological model to the circulation model. The biological model describes some overall effects of production, sinking, and decomposition of organic matter. First a standard case of the biological model is presented. This is followed by some modified cases. It is shown that the observed nutrient distribution including the maximum can be generated. The available nutrient data from the Arctic Ocean are not sufficient to decide which among the cases is the most likely to occur. One case is, however, chosen as the best case. A nutrient budget and estimates of the magnitudes of the new production are presented for this case.

Winter bloom of a rare betaproteobacterium in the Arctic Ocean

PubMed Central

Alonso-Sáez, Laura; Zeder, Michael; Harding, Tommy; Pernthaler, Jakob; Lovejoy, Connie; Bertilsson, Stefan; Pedrós-Alió, Carlos

2014-01-01

Extremely low abundance microorganisms (members of the “rare biosphere”) are believed to include dormant taxa, which can sporadically become abundant following environmental triggers. Yet, microbial transitions from rare to abundant have seldom been captured in situ, and it is uncertain how widespread these transitions are. A bloom of a single ribotype (≥99% similarity in the 16S ribosomal RNA gene) of a widespread betaproteobacterium (Janthinobacterium sp.) occurred over 2 weeks in Arctic marine waters. The Janthinobacterium population was not detected microscopically in situ in January and early February, but suddenly appeared in the water column thereafter, eventually accounting for up to 20% of bacterial cells in mid February. During the bloom, this bacterium was detected at open water sites up to 50 km apart, being abundant down to more than 300 m. This event is one of the largest monospecific bacterial blooms reported in polar oceans. It is also remarkable because Betaproteobacteria are typically found only in low abundance in marine environments. In particular, Janthinobacterium were known from non-marine habitats and had previously been detected only in the rare biosphere of seawater samples, including the polar oceans. The Arctic Janthinobacterium formed mucilagenous monolayer aggregates after short (ca. 8 h) incubations, suggesting that biofilm formation may play a role in maintaining rare bacteria in pelagic marine environments. The spontaneous mass occurrence of this opportunistic rare taxon in polar waters during the energy-limited season extends current knowledge of how and when microbial transitions between rare and abundant occur in the ocean. PMID:25191307

Early Student Support for the Study of Inertial Motions in the Arctic Ocean

DTIC Science & Technology

2015-09-30

Dosser, Hayley V., Sasan J. Ghaemsaidi, Thomas Peacock , and Luc Rainville, x. Internal Wave 5 Propagation and Stability in the Western Arctic...Ocean. In preparation for J. Phys. Oceanogr. Ghaemsaidi, Sasan J., Hayley V. Dosser, Luc Rainville, and Thomas Peacock , 2015. The impact of multiple

Plate tectonic history of the Arctic

NASA Technical Reports Server (NTRS)

Burke, K.

1984-01-01

Tectonic development of the Arctic Ocean is outlined, and geological maps are provided for the Arctic during the mid-Cenozoic, later Cretaceous, late Jurassic, early Cretaceous, early Jurassic and late Devonian. It is concluded that Arctic basin history is moulded by the events of the following intervals: (1) continental collision and immediately subsequent rifting and ocean formation in the Devonian, and continental rifting ocean formation, rapid rotation of microcontinents, and another episode of collision in the latest Jurassic and Cretaceous. It is noted that Cenozoic Arctic basin formation is a smaller scale event superimposed on the late Mesozoic ocean basin.

"Cold" Fixation: Reconciliation of Nitrogen Fixation Rates and Diazotroph Assemblages in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Fong, A. A.; Waite, A.; Rost, B.; Richter, K. U.

2016-02-01

Measurements of biological nitrogen fixation are typically conducted in oligotrophic subtropical and tropical marine environments where concentrations of fixed inorganic nitrogen are low. To date, only a handful of nitrogen fixation studies have been conducted in high latitude marine environments, but further investigation is needed to resolve the distribution of cold ocean diazotrophic assemblages. Nitrogen fixation rates and nifH gene distributions were measured at seven stations from 5°E to 20°E, north of 81°N in the Arctic Ocean at the onset of summer 2015. Discrete water samples in ice-covered regions were collected from the sea surface to 200 m for 15N2-tracer additions and targeted nifH gene and transcript analyses. Previous work suggests that heterotrophic bacteria dominate diazotrophic communities in the Arctic Ocean. Therefore, additional nifH gene surveys of sinking particles were conducted to test for enrichment on organic matter-rich microenvironments. Together, these measurements aim to reconcile diazotrophic activity with microbial community composition, further elucidating how nitrogen fixers could impact current concepts in polar carbon and nutrient cycling.

A Giant Arctic Freshwater Pond at the end of the Early Eocene; Implications for Ocean Heat Transport and Carbon Cycling

NASA Astrophysics Data System (ADS)

Brinkhuis, H.; Schouten, S.; Collinson, M. E.; Sluijs, A.; Sinninghe-Damste, J. S.; Dickens, G. R.; Huber, M.; Cronin, T. M.; Bujak, J. P.; Stein, R.; Eldrett, J. S.; Harding, I. C.; Sangiorgi, F.

2005-12-01

In the last decades remains of the free-floating, fresh water fern Azolla have been found in unusually high abundances in basal middle Eocene (~48.5 Ma) marine sediments deposited in all Nordic seas. While generally taken to signal some `freshwater input', their source and significance were not determined. Through palynological and organic geochemical analyses of unique cores obtained from unprecedented Arctic Ocean drilling (IODP 302 - ACEX) we show that the brackish surface conditions that prevailed in the Arctic Ocean through the late Paleocene and early Eocene culminated in the deposition of laminated organic rich deposits yielding huge amounts of remains of Azolla. This, plus e.g., low diversity dinoflagellate assemblages, and concomitant low BIT values, indicates in-situ Azolla growth, and that the surface of the Arctic Ocean episodically resembled a giant fresh water pond over an interval altogether lasting ~800,000 years. The Arctic Basin thus constituted the main source of the freshwater pulses found elsewhere, reaching as far south as the southern North Sea.TEX86-derived surface temperatures were 13-14°C before and after the Azolla interval and only 10°C during the event, which may be related to obstruction of pole ward ocean heat transport and/or increased carbon burial.

An Arctic Ocean freshwater event as the trigger of the Younger Dryas stadial? Answers from Arctic deep-sea sediment cores

NASA Astrophysics Data System (ADS)

Spielhagen, Robert F.

2017-04-01

At ca. 12.8-11.5 ka the northern hemisphere climate experienced a dramatic fall-back to quasi-glacial conditions. Since the late 1980s, a major meltwater ejection to the North Atlantic through the Gulf of St.Lawrence was considered the most likely trigger for this "Younger Dryas event". It may have caused a slowdown of the Atlantic meridional overturning circulation (AMOC) and a diminished heat transport to the northern latitudes. However, field evidence from the potential meltwater route in North America has been discussed controversially in the last years, and the detection of a freshwater signal in marine sediments off the St.Lawrence river rendered difficult. More recently, the idea of an "Arctic route" of meltwater originating from proglacial lake Agassiz was put forward (Tarasov & Peltier, Nature 2005) and has gained further attraction through evidence from radiogenic isotopes (Not and Hillaire-Marcel; Nature Comm., 2012) and through modelling results of Condron and Winsor (PNAS, 2012) which showed that only a freshwater outflow through Fram Strait was capable of triggering a climate perturbation like the Younger Dryas. Here I present a review of isotopic records from the Arctic Ocean, the Fram Strait, and the Greenland Sea in search of evidence for a strong freshwater event in the Arctic Ocean at the onset of the Younger Dryas, supporting an Arctic origin of the trigger. A number of Arctic cores show a light planktic oxygen isotope spike at 13 ka. For several of them the age model is detailed enough to exclude a confusion with other deglacial spikes. On the central Arctic Lomonosov Ridge there is even evidence for a diminshed intermediate/bottom water circulation immediately following the freshwater event. On the other hand, there are many records which do not show a meltwater spike in the critical time interval, most likely because of low temporal resolution, a thick ice cover and/or a habitat change of the planktic foraminifers. The largest uncertainty is

Contrasting physiological responses to future ocean acidification among Arctic copepod populations.

PubMed

Thor, Peter; Bailey, Allison; Dupont, Sam; Calosi, Piero; Søreide, Janne E; De Wit, Pierre; Guscelli, Ella; Loubet-Sartrou, Lea; Deichmann, Ida M; Candee, Martin M; Svensen, Camilla; King, Andrew L; Bellerby, Richard G J

2018-01-01

Widespread ocean acidification (OA) is modifying the chemistry of the global ocean, and the Arctic is recognized as the region where the changes will progress at the fastest rate. Moreover, Arctic species show lower capacity for cellular homeostasis and acid-base regulation rendering them particularly vulnerable to OA. In the present study, we found physiological differences in OA response across geographically separated populations of the keystone Arctic copepod Calanus glacialis. In copepodites stage CIV, measured reaction norms of ingestion rate and metabolic rate showed severe reductions in ingestion and increased metabolic expenses in two populations from Svalbard (Kongsfjord and Billefjord) whereas no effects were observed in a population from the Disko Bay, West Greenland. At pH T 7.87, which has been predicted for the Svalbard west coast by year 2100, these changes resulted in reductions in scope for growth of 19% in the Kongsfjord and a staggering 50% in the Billefjord. Interestingly, these effects were not observed in stage CV copepodites from any of the three locations. It seems that CVs may be more tolerant to OA perhaps due to a general physiological reorganization to meet low intracellular pH during hibernation. Needless to say, the observed changes in the CIV stage will have serious implications for the C. glacialis population health status and growth around Svalbard. However, OA tolerant populations such as the one in the Disko Bay could help to alleviate severe effects in C. glacialis as a species. © 2017 John Wiley & Sons Ltd.

Pliocene cooling enhanced by flow of low-salinity Bering Sea water to the Arctic Ocean.

PubMed

Horikawa, Keiji; Martin, Ellen E; Basak, Chandranath; Onodera, Jonaotaro; Seki, Osamu; Sakamoto, Tatsuhiko; Ikehara, Minoru; Sakai, Saburo; Kawamura, Kimitaka

2015-06-29

Warming of high northern latitudes in the Pliocene (5.33-2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep Water formation and enhancing sea ice formation. However, the timing of Arctic freshening has not been defined. Here we present neodymium and lead isotope records of detrital sediment from the Bering Sea for the past 4.3 million years. Isotopic data suggest the presence of Alaskan glaciers as far back as 4.2 Myr ago, while diatom and C37:4 alkenone records show a long-term trend towards colder and fresher water in the Bering Sea beginning with the M2 glaciation (3.3 Myr ago). We argue that the introduction of low-salinity Bering Sea water to the Arctic Ocean by 3.3 Myr ago preconditioned the climate system for global cooling.

Pliocene cooling enhanced by flow of low-salinity Bering Sea water to the Arctic Ocean

PubMed Central

Horikawa, Keiji; Martin, Ellen E.; Basak, Chandranath; Onodera, Jonaotaro; Seki, Osamu; Sakamoto, Tatsuhiko; Ikehara, Minoru; Sakai, Saburo; Kawamura, Kimitaka

2015-01-01

Warming of high northern latitudes in the Pliocene (5.33–2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep Water formation and enhancing sea ice formation. However, the timing of Arctic freshening has not been defined. Here we present neodymium and lead isotope records of detrital sediment from the Bering Sea for the past 4.3 million years. Isotopic data suggest the presence of Alaskan glaciers as far back as 4.2 Myr ago, while diatom and C37:4 alkenone records show a long-term trend towards colder and fresher water in the Bering Sea beginning with the M2 glaciation (3.3 Myr ago). We argue that the introduction of low-salinity Bering Sea water to the Arctic Ocean by 3.3 Myr ago preconditioned the climate system for global cooling. PMID:26119338

High Resolution Tidal Modelling in the Arctic Ocean: Needs and Upcoming Developments

NASA Astrophysics Data System (ADS)

Cancet, M.; Andersen, O.; Stenseng, L.; Lyard, F.; Cotton, D.; Benveniste, J.; Schulz, A.

2015-12-01

The Arctic Ocean is a challenging region for tidal modelling, because of its complex and not well-documented bathymetry, together combined with the intermittent presence of sea ice and the fact that the in situ tidal observations are rather scarce at such high latitudes. As a consequence, the accuracy of the global tidal models decreases by several centimetres in the Polar Regions. In particular, it has a large impact on the quality of the satellite altimeter sea surface heights in these regions (ERS1/2, Envisat, CryoSat-2, SARAL/AltiKa and the future Sentinel-3 mission). Better knowledge of the tides would improve the quality of the high latitudes altimeter sea surface heights and of all derived products, such as the altimetry-derived geostrophic currents, the mean sea surface and the mean dynamic topography. In addition, accurate tidal models are highly strategic information for ever-growing maritime and industrial activities in this region. NOVELTIS and DTU Space are currently working on the development of a regional, high-resolution tidal atlas in the Arctic Ocean. In particular, this atlas will benefit from the assimilation of the most complete satellite altimetry dataset ever used in this region, including Envisat data up to 82°N and the CryoSat-2 reprocessed data between 82°N and 88°N. The combination of all these satellites will give the best possible coverage of altimetry-derived tidal constituents. The available tide gauge data will also be used either for assimilation or validation. This paper presents the performances of the available global tidal models in the Arctic Ocean and the on-going development of an improved regional tidal atlas in this region.

High resolution tidal modeling in the Arctic Ocean: needs and upcoming developments

NASA Astrophysics Data System (ADS)

Cancet, Mathilde; Baltazar Andersen, Ole; Cotton, David; Lyard, Florent; Benveniste, Jerome

2015-04-01

The Arctic Ocean is a challenging region for tidal modeling, because of its complex and not well-documented bathymetry, combined with the intermittent presence of sea ice and the fact that the in situ tidal observations are rather scarce at high latitudes. As a consequence, the accuracy of the global tidal models decreases by several centimeters in the Polar Regions. As a consequence the quality of the satellite altimeter sea surface heights in these regions (ERS1/2, Envisat, CryoSat-2, SARAL/AltiKa and the future Sentinel-3 mission) are impacted. Better knowledge of the tides would improve the quality of the high latitudes altimeter sea surface heights and of all derived products, such as the altimetry-derived geostrophic currents, the mean sea surface and the mean dynamic topography. In addition, accurate tidal models are highly strategic information for ever-growing maritime and industrial activities in this region. NOVELTIS and DTU Space are currently working on the development of a regional, high-resolution tidal atlas in the Arctic Ocean. In particular, this atlas will benefit from the assimilation of the most complete satellite altimetry dataset ever used in this region, including Envisat and SARAL/AltiKa data up to 82°N and the CryoSat-2 reprocessed data between 82°N and 88°N. The combination of all these satellites will give the best possible coverage of altimetry-derived tidal constituents. The available tide gauge data will also be used either for assimilation or validation. This paper presents the deficiencies and needs of the global tidal models in the Arctic Ocean as identified using the CryoSat altimetry data, and the on-going work to develop an improved regional tidal atlas in this region.

Microorganisms in small patterned ground features and adjacent vegetated soils along topographic and climatic gradients in the High Arctic, Canada

Treesearch

G. Gonzalez; F.J. Rivera-Figueroa; W. Gould; S.A. Cantrell; J.R. Pérez-Jiménez

2014-01-01

In this study, we determine differences in total biomass of soil microorganisms and community structure (using the most probable number of bacteria (MPN) and the number of fungal genera) in patterned ground features (PGF) and adjacent vegetated soils (AVS) in mesic sites from three High Arctic islands in order to characterize microbial dynamics as affected by...

Evidence for ice-free summers in the late Miocene central Arctic Ocean

PubMed Central

Stein, Ruediger; Fahl, Kirsten; Schreck, Michael; Knorr, Gregor; Niessen, Frank; Forwick, Matthias; Gebhardt, Catalina; Jensen, Laura; Kaminski, Michael; Kopf, Achim; Matthiessen, Jens; Jokat, Wilfried; Lohmann, Gerrit

2016-01-01

Although the permanently to seasonally ice-covered Arctic Ocean is a unique and sensitive component in the Earth's climate system, the knowledge of its long-term climate history remains very limited due to the restricted number of pre-Quaternary sedimentary records. During Polarstern Expedition PS87/2014, we discovered multiple submarine landslides along Lomonosov Ridge. Removal of younger sediments from steep headwalls has led to exhumation of Miocene sediments close to the seafloor. Here we document the presence of IP25 as a proxy for spring sea-ice cover and alkenone-based summer sea-surface temperatures >4 °C that support a seasonal sea-ice cover with an ice-free summer season being predominant during the late Miocene in the central Arctic Ocean. A comparison of our proxy data with Miocene climate simulations seems to favour either relatively high late Miocene atmospheric CO2 concentrations and/or a weak sensitivity of the model to simulate the magnitude of high-latitude warming in a warmer than modern climate. PMID:27041737

The pressure ridge distribution in the Arctic Ocean from submarine sonar data

NASA Astrophysics Data System (ADS)

Rodrigues, Joao; Wadhams, Peter

2010-05-01

The profiling of the underside of the sea ice with upward-looking sonars fitted to submarines is the best method of studying the large scale distribution of morphological features such as pressure ridges and leads. We present the statistical analysis of the distributions of pressure ridge spacings and heights, and lead spacings and widths observed during two Arctic cruises by the Royal Navy submarine HMS Tireless in the winters of 2004 and 2007 in which more than 10000km of sea ice draft data were collected. We briefly describe the main characteristics of the full ice draft distribution in the several regions of the Arctic Ocean visited by the submarine and discuss the most significant differences between 2004 and 2007. In the area of heavily ridged ice north of Greenland and Ellesmere Island we found an increase in ridge density (number of ridges per unit track length) accompanied by a decrease in modal ice draft, leaving the mean ice thickness essentially unchanged, between 2004 and 2007. This area is likely to be the only one in the Arctic Ocean where the sea ice thickness may not be in decline. We investigate the causes of this invariance in the context of an Arctic Ocean in transition from a multi-year to a first-year ice cover and discuss its relation with the strengthening of the transpolar drift and consequent accumulation of ice north of Greenland and increase in ice export through Fram Strait. Our analysis shows that the number of deep ridges per km is well described by a Poisson distribution while the corresponding distribution for shallow ridges is more complicated. The tail of the distribution of the pressure ridge heights is approximately a negative exponential, in agreement with similar observations made in previous cruises. We pay special attention to the uncertainties and biases in the measurement of the ice draft. Specifically, we discuss the effects of the finite beamwidth of the single-beam sonars traditionally used in British submarines on the

Formation of a CliC/CLIVAR Northern Oceans Regional Panel to advance the understanding of the role of the Arctic in global climate

NASA Astrophysics Data System (ADS)

Solomon, A.

2017-12-01

The Arctic climate is rapidly transitioning into a new regime with lower sea ice extent and increasingly younger and thinner sea ice pack. The emergent properties of this new regime are yet to be determined since altered feedback processes between ice, ocean, and atmosphere will further impact upper ocean heat content, atmospheric circulation, atmospheric and oceanic stratification, the interactions between subsurface/intermediate warm waters and surface cold and fresh layer, cloud cover, ice growth, among other properties. This emergent new climate regime needs to be understood in terms of the two-way feedback between the Arctic and lower-latitudes (both in the ocean and atmosphere), as well as the local coupling between ocean-sea ice-atmosphere. The net result of these feedbacks will determine the magnitude of future Arctic amplification and potential impacts on mid-latitude weather extremes, among other impacts. A new international panel, the CliC/CLIVAR Northern Oceans Regional Panel, has been established to coordinate efforts that will enhance our ability to monitor the coupled system, understand the driving mechanisms of the system change from a coupled process perspective, and predict the evolution of the emerging "New Arctic" climate. This talk will discuss the scientific motivation for this new panel, the near-term objectives, and plans for deliverables.

The role of sustained observations and data co-management in Arctic Ocean governance

NASA Astrophysics Data System (ADS)

Eicken, H.; Lee, O. A.; Rupp, S. T.; Trainor, S.; Walsh, J. E.

2015-12-01

Rapid environmental change, a rise in maritime activities and resource development, and increasing engagement by non-Arctic nations are key to major shifts underway in Arctic social-environmental systems (SES). These shifts are triggering responses by policy makers, regulators and a range of other actors in the Arctic Ocean region. Arctic science can play an important role in informing such responses, in particular by (i) providing data from sustained observations to serve as indicators of change and major transitions and to inform regulatory and policy response; (ii) identifying linkages across subsystems of Arctic SES and across regions; (iii) providing predictions or scenarios of future states of Arctic SES; and (iv) informing adaptation action in response to rapid change. Policy responses to a changing Arctic are taking a multi-faceted approach by advancing international agreements through the Arctic Council (e.g., Search and Rescue Agreement), global forums (e.g., IMO Polar Code) or private sector instruments (e.g., ISO code for offshore structures). At the regional level, co-management of marine living resources involving local, indigenous stakeholders has proven effective. All of these approaches rely on scientific data and information for planning and decision-making. Examples from the Pacific Arctic sector illustrate how such relevant data is currently collected through a multitude of different government agencies, universities, and private entities. Its effective use in informing policy, planning and emergency response requires coordinated, sustained acquisition, common standards or best practices, and data sharing agreements - best achieved through data co-management approaches. For projections and scenarios of future states of Arctic SES, knowledge co-production that involves all relevant stakeholders and specifically addresses major sources of uncertainty is of particular relevance in an international context.

Inter-annual variability of transparent exopolymer particles in the Arctic Ocean reveals high sensitivity to ecosystem changes.

PubMed

Engel, Anja; Piontek, Judith; Metfies, Katja; Endres, Sonja; Sprong, Pim; Peeken, Ilka; Gäbler-Schwarz, Steffi; Nöthig, Eva-Maria

2017-06-23

Transparent exopolymer particles (TEP) are a class of marine gel particles and important links between surface ocean biology and atmospheric processes. Derived from marine microorganisms, these particles can facilitate the biological pumping of carbon dioxide to the deep sea, or act as cloud condensation and ice nucleation particles in the atmosphere. Yet, environmental controls on TEP abundance in the ocean are poorly known. Here, we investigated some of these controls during the first multiyear time-series on TEP abundance for the Fram Strait, the Atlantic gateway to the Central Arctic Ocean. Data collected at the Long-Term Ecological Research observatory HAUSGARTEN during 2009 to 2014 indicate a strong biological control with highest abundance co-occurring with the prymnesiophyte Phaeocystis pouchetii. Higher occurrence of P. pouchetii in the Arctic Ocean has previously been related to northward advection of warmer Atlantic waters, which is expected to increase in the future. Our study highlights the role of plankton key species in driving climate relevant processes; thus, changes in plankton distribution need to be accounted for when estimating the ocean's biogeochemical response to global change.

Observed microphysical changes in Arctic mixed-phase clouds when transitioning from sea-ice to open ocean

NASA Astrophysics Data System (ADS)

Young, Gillian; Jones, Hazel M.; Crosier, Jonathan; Bower, Keith N.; Darbyshire, Eoghan; Taylor, Jonathan W.; Liu, Dantong; Allan, James D.; Williams, Paul I.; Gallagher, Martin W.; Choularton, Thomas W.

2016-04-01

The Arctic sea-ice is intricately coupled to the atmosphere[1]. The decreasing sea-ice extent with the changing climate raises questions about how Arctic cloud structure will respond. Any effort to answer these questions is hindered by the scarcity of atmospheric observations in this region. Comprehensive cloud and aerosol measurements could allow for an improved understanding of the relationship between surface conditions and cloud structure; knowledge which could be key in validating weather model forecasts. Previous studies[2] have shown via remote sensing that cloudiness increases over the marginal ice zone (MIZ) and ocean with comparison to the sea-ice; however, to our knowledge, detailed in-situ data of this transition have not been previously presented. In 2013, the Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign was carried out in the vicinity of Svalbard, Norway to collect in-situ observations of the Arctic atmosphere and investigate this issue. Fitted with a suite of remote sensing, cloud and aerosol instrumentation, the FAAM BAe-146 aircraft was used during the spring segment of the campaign (Mar-Apr 2013). One case study (23rd Mar 2013) produced excellent coverage of the atmospheric changes when transitioning from sea-ice, through the MIZ, to the open ocean. Clear microphysical changes were observed, with the cloud liquid-water content increasing by almost four times over the transition. Cloud base, depth and droplet number also increased, whilst ice number concentrations decreased slightly. The surface warmed by ~13 K from sea-ice to ocean, with minor differences in aerosol particle number (of sizes corresponding to Cloud Condensation Nuclei or Ice Nucleating Particles) observed, suggesting that the primary driver of these microphysical changes was the increased heat fluxes and induced turbulence from the warm ocean surface as expected. References: [1] Kapsch, M.L., Graversen, R.G. and Tjernström, M. Springtime

Philinidae, Laonidae and Philinorbidae (Gastropoda: Cephalaspidea: Philinoidea) from the northeastern Pacific Ocean and the Beaufort Sea (Arctic Ocean).

PubMed

Valdés, Ángel; Cadien, Donald B; Gosliner, Terrence M

2016-08-08

Based on morphological data a total of nine native species of Philinidae are recognized from the northeastern Pacific including the Bering Sea and the adjacent Arctic Ocean (Beaufort Sea). Four of them have been previously described: Philine ornatissima Yokoyama, 1927, Philine bakeri Dall, 1919, Philine polystrigma (Dall, 1908), and Philine hemphilli Dall, 1919. Five of them are new and described herein: Philine mcleani sp. nov., Philine baxteri sp. nov., Philine malaquiasi sp. nov., Philine wareni sp. nov., and Philine harrisae sp. nov. These species display a substantial degree of variation in internal and external morphological traits (i.e., presence/absence of gizzard plates, different radular structure and tooth morphology, various reproductive anatomical features) and it is likely that they belong to different clades (genera). However, in the absence of a comprehensive phylogeny for Philine, they are here provisionally regarded as Philine sensu lato. In addition to the nine native species, two introduced species: Philine orientalis A. Adams, 1854 and Philine auriformis Suter, 1909 are here illustrated and compared to the native species to facilitate identification. Finally, two species previously considered members of Philinidae are examined anatomically and confirmed as members of Laonidae, Laona californica (Willett, 1944) and Philinorbidae, Philinorbis albus (Mattox, 1958), based on morphological data.

Introduction to special section on Annual Cycles on the Arctic Ocean Shelf

NASA Astrophysics Data System (ADS)

Fortier, Louis; Cochran, J. Kirk

2008-03-01

The perennial sea-ice cover of the Arctic Ocean is shrinking rapidly in response to the anthropogenic warming of Earth's lower atmosphere. From September 2002 to September 2004 the Canadian Arctic Shelf Exchange Study (CASES) logged over 14,500 scientist-days at sea to document the potential impacts of a shift in sea-ice regime on the ecosystem of the Mackenzie Shelf in the southeastern Beaufort Sea. In particular, teams from Canada, Denmark, Japan, Norway, Spain, the United Kingdom, and the United States totaling over 200 scientists took rotations on the CCS Amundsen to study all aspects of the ecosystem during a 385-day over-wintering expedition in the region from September 2003 to September 2004. The resulting wealth of information has revealed an unexpectedly active food web under the winter sea ice of the coastal Beaufort Sea. From the thermodynamics of snow to the reconstruction of local paleo-climate, this special section focuses on how sea-ice cover dynamics dictate biological processes and biogeochemical fluxes on and at the margin of the shallow Arctic continental shelf. The highly successful CASES program has initiated ongoing time series of key measurements of the response of the marine ecosystem to change that have been expanded to other Arctic regions through the ArcticNet project and the International Polar Year.

Circumpolar measurements of speciated mercury, ozone and carbon monoxide in the boundary layer of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Sommar, J.; Andersson, M. E.; Jacobi, H.-W.

2009-10-01

Using the Swedish icebreaker Oden as a platform, continuous measurements of airborne mercury (gaseous elemental mercury (Hg0), divalent mercury HgII(g) (acronym RGM) and mercury attached to particles (PHg)) and some long-lived trace gases (carbon monoxide CO and ozone O3) were performed over the North Atlantic and the Arctic Ocean. The measurements were performed for nearly three months (July-September, 2005) during the Beringia 2005 expedition (from Göteborg, Sweden via the proper Northwest Passage to the Beringia region Alaska - Chukchi Penninsula - Wrangel Island and in-turn via a north-polar transect to Longyearbyen, Spitsbergen). The Beringia 2005 expedition was the first time that these species have been measured during summer over the Arctic Ocean going from 60° to 90° N. During the North Atlantic transect, concentration levels of Hg0, CO and O3 were measured comparable to typical levels for the ambient mid-hemispheric average. However, a rapid increase of Hg0 in air and surface water was observed when entering the ice-covered waters of the Canadian Arctic archipelago. Large parts of the measured waters were supersaturated with respect to Hg0, reflecting a strong disequilibrium. Heading through the sea ice of the Arctic Ocean, a fraction of the strong Hg0} pulse in the water was spilled with some time-delay into the air samples collected 20 m a.s.l. Several episodes of elevated Hg0(g) were encountered along the sea ice route with higher mean concentration (1.81±0.43 ng m-3) compared to the marine boundary layer over ice-free oceanic waters (1.55±0.21 ng m-3). In addition, an overall majority of the variance in the temporal series of Hg0 concentrations was observed during July. Atmospheric boundary layer {O3} mixing ratios decreased when initially sailing northward. In the Arctic, an O3 minimum around 15-20 ppbv was observed during summer (July-August). Alongside the polar transect during the beginning of autumn, a steady trend of increasing O3 mixing

Late Quaternary sediment deposition of core MA01 in the Mendeleev Ridge, the western Arctic Ocean: Preliminary results

NASA Astrophysics Data System (ADS)

Park, Kwang-Kyu; Kim, Sunghan; Khim, Boo-Keun; Xiao, Wenshen; Wang, Rujian

2014-05-01

Late Quaternary deep marine sediments in the Arctic Ocean are characterized by brown layers intercalated with yellowish to olive gray layers (Poore et al., 1999; Polyak et al., 2004). Previous studies reported that the brown and gray layers were deposited during interglacial (or interstadial) and glacial (or stadial) periods, respectively. A 5.5-m long gravity core MA01 was obtained from the Mendeleev Ridge in the western Arctic Ocean by R/V Xue Long during scientific cruise CHINARE-V. Age (~450 ka) of core MA01 was tentatively estimated by correlation of brown layers with an adjacent core HLY0503-8JPC (Adler et al., 2009). A total of 22 brown layers characterized by low L* and b*, high Mn concentration, and abundant foraminifera were identified. Corresponding gray layers are characterized by high L* and b*, low Mn concentration, and few foraminiferal tests. Foraminifera abundance peaks are not well correlated to CaCO3 peaks which occurred with the coarse-grained (>0.063 mm) fractions (i.e., IRD) both in brown and gray layers. IRDs are transported presumably by sea ice for the deposition of brown layers and by iceberg for the deposition of gray layers (Polyak et al., 2004). A strong correlation coefficient (r2=0.89) between TOC content and C/N ratio indicates that the major source of organic matter is terrestrial. The good correlations of CaCO3 content to TOC (r2=0.56) and C/N ratio (r2=0.69) imply that IRDs contain detrital CaCO3 which mainly originated from the Canadian Arctic Archipelago. In addition, high kaolinite/chlorite (K/C) ratios mostly correspond to CaCO3 peaks, which suggests that the fine-grained particles in the Mendeleev Ridge are transported from the north coast Alaska and Canada where Mesozoic and Cenozoic strata are widely distributed. Thus, the Beaufort Gyre, the predominant surface current in the western Arctic Ocean, played an important role in the sediment delivery to the Mendeleev Ridge. It is worthy of note that the TOC and CaCO3 peaks are

Collection of Arctic Ocean Data from US Navy Submarines on the New SCICEX Program

NASA Astrophysics Data System (ADS)

Smethie, W. M.; Sambrotto, R.; Boyd, T.; Richter-Menge, J.; Corbett, J.

2011-12-01

The SCICEX submarine Arctic science program originated in the 1990s when six dedicated science cruises were conducted in the Arctic Ocean aboard US Navy Sturgeon class submarines. After the cold war era Sturgeon class submarines were retired, several Science Accommodation cruises, for which a few days for scientific measurements were added to planned submarine transits through the Arctic Ocean, were carried out when opportunities arose. Renewed interest in conducting further Science Accommodation cruises on a regular basis to better document and understand how the Arctic Ocean responds to climate change resulted in publication of a scientific plan in 2010 (http://www.arctic.gov/publications/scicex_plan.pdf). In the spring of 2011 testing of data collection and water sampling methods aboard newer Virginia and Seawolf class submarines on transit from a Navy ice camp in the Beaufort Sea, was conducted in order to develop protocols and evaluate techniques. Ice draft measurements were also taken in the vicinity of the ice camp and near the North Pole to evaluate new data collection systems. This evaluation will include a comparison of the ice draft data with a comprehensive set of in situ ice thickness measurements taken near the ice camp. Under-ice submarine-launched eXpendable Condutivity Temperature Depth (XCTD) probes were deployed from the USS Connecticut (SSN-22), a Seawolf class submarine, and the resulting profiles compared to CTD casts from the APLIS ice station and historical profiles. Water samples were collected through the hull for measurements of tritium, helium isotopes, oxygen isotopes, chlorofluorocarbons, sulfur hexafluoride, nutrients, dissolved organic carbon, bacterioplankton, phytoplankton and particulates levels. These samples were returned to Lamont-Doherty Earth Observatory and were in the process of being measured at the time this abstract was written. Measurements completed at this time indicate good samples can be collected for CFC-12

Late Eocene to present isotopic (Sr-Nd-Pb) and geochemical evolution of sediments from the Lomonosov Ridge, Arctic Ocean: Implications for continental sources and linkage with the North Atlantic Ocean

NASA Astrophysics Data System (ADS)

Stevenson, Ross; Poirier, André; Véron, Alain; Carignan, Jean; Hillaire-Marcel, Claude

2015-09-01

New geochemical and isotopic (Sr, Nd, Pb) data are presented for a composite sedimentary record encompassing the past 50 Ma of history of sedimentation on the Lomonosov Ridge in the Arctic Ocean. The sampled sediments encompass the transition of the Arctic basin from an enclosed anoxic basin to an open and ventilated oxidized ocean basin. The transition from anoxic basin to open ventilated ocean is accompanied by at least three geochemical and isotopic shifts and an increase in elements (e.g., K/Al) controlled by detrital minerals highlighting significant changes in sediment types and sources. The isotopic compositions of the sediments prior to ventilation are more variable but indicate a predominance of older crustal contributions consistent with sources from the Canadian Shield. Following ventilation, the isotopic compositions are more stable and indicate an increased contribution from younger material consistent with Eurasian and Pan-African crustal sources. The waxing and waning of these sources in conjunction with the passage of water through Fram Strait underlines the importance of the exchange of water mass between the Arctic and North Atlantic Oceans.

Postglacial response of Arctic Ocean gas hydrates to climatic amelioration

PubMed Central

Serov, Pavel; Mienert, Jürgen; Patton, Henry; Portnov, Alexey; Silyakova, Anna; Panieri, Giuliana; Carroll, Michael L.; Carroll, JoLynn; Andreassen, Karin; Hubbard, Alun

2017-01-01

Seafloor methane release due to the thermal dissociation of gas hydrates is pervasive across the continental margins of the Arctic Ocean. Furthermore, there is increasing awareness that shallow hydrate-related methane seeps have appeared due to enhanced warming of Arctic Ocean bottom water during the last century. Although it has been argued that a gas hydrate gun could trigger abrupt climate change, the processes and rates of subsurface/atmospheric natural gas exchange remain uncertain. Here we investigate the dynamics between gas hydrate stability and environmental changes from the height of the last glaciation through to the present day. Using geophysical observations from offshore Svalbard to constrain a coupled ice sheet/gas hydrate model, we identify distinct phases of subglacial methane sequestration and subsequent release on ice sheet retreat that led to the formation of a suite of seafloor domes. Reconstructing the evolution of this dome field, we find that incursions of warm Atlantic bottom water forced rapid gas hydrate dissociation and enhanced methane emissions during the penultimate Heinrich event, the Bølling and Allerød interstadials, and the Holocene optimum. Our results highlight the complex interplay between the cryosphere, geosphere, and atmosphere over the last 30,000 y that led to extensive changes in subseafloor carbon storage that forced distinct episodes of methane release due to natural climate variability well before recent anthropogenic warming. PMID:28584081

Vulnerability of polar oceans to anthropogenic acidification: comparison of arctic and antarctic seasonal cycles.

PubMed

Shadwick, E H; Trull, T W; Thomas, H; Gibson, J A E

2013-01-01

Polar oceans are chemically sensitive to anthropogenic acidification due to their relatively low alkalinity and correspondingly weak carbonate buffering capacity. Here, we compare unique CO2 system observations covering complete annual cycles at an Arctic (Amundsen Gulf) and Antarctic site (Prydz Bay). The Arctic site experiences greater seasonal warming (10 vs 3°C), and freshening (3 vs 2), has lower alkalinity (2220 vs 2320 μmol/kg), and lower summer pH (8.15 vs 8.5), than the Antarctic site. Despite a larger uptake of inorganic carbon by summer photosynthesis, the Arctic carbon system exhibits smaller seasonal changes than the more alkaline Antarctic system. In addition, the excess surface nutrients in the Antarctic may allow mitigation of acidification, via CO2 removal by enhanced summer production driven by iron inputs from glacial and sea-ice melting. These differences suggest that the Arctic system is more vulnerable to anthropogenic change due to lower alkalinity, enhanced warming, and nutrient limitation.

Vulnerability of Polar Oceans to Anthropogenic Acidification: Comparison of Arctic and Antarctic Seasonal Cycles

PubMed Central

Shadwick, E. H.; Trull, T. W.; Thomas, H.; Gibson, J. A. E.

2013-01-01

Polar oceans are chemically sensitive to anthropogenic acidification due to their relatively low alkalinity and correspondingly weak carbonate buffering capacity. Here, we compare unique CO2 system observations covering complete annual cycles at an Arctic (Amundsen Gulf) and Antarctic site (Prydz Bay). The Arctic site experiences greater seasonal warming (10 vs 3°C), and freshening (3 vs 2), has lower alkalinity (2220 vs 2320 μmol/kg), and lower summer pH (8.15 vs 8.5), than the Antarctic site. Despite a larger uptake of inorganic carbon by summer photosynthesis, the Arctic carbon system exhibits smaller seasonal changes than the more alkaline Antarctic system. In addition, the excess surface nutrients in the Antarctic may allow mitigation of acidification, via CO2 removal by enhanced summer production driven by iron inputs from glacial and sea-ice melting. These differences suggest that the Arctic system is more vulnerable to anthropogenic change due to lower alkalinity, enhanced warming, and nutrient limitation. PMID:23903871

Anthropogenic 129I in the North Pacific, Bering and Chukchi Seas, and Arctic Ocean in 2012-2013

NASA Astrophysics Data System (ADS)

Nagai, H.; Hasegawa, A.; Yamagata, T.; Kumamoto, Y.; Nishino, S.; Matsuzaki, H.

2015-10-01

Most of anthropogenic 129I in marine environment are due to discharge from the nuclear fuel reprocessing facilities at Sellafield (U.K.) and La Hague (France) for past few decades. The discharge raised 129I concentration in seawaters in the North Atlantic and Arctic Oceans to more than 109 atoms L-1, which is two orders of magnitude higher than that in other region. Recently, in March 2011, a large quantity of 129I was released into the western North Pacific due to the Fukushima Daiichi Nuclear Power Plant (F1NPP) accident. To evaluate the influence of these events, we have measured 129I concentration in seawaters in the northern North Pacific Ocean, Bering and Chukchi Seas, and Arctic Ocean in 2012-2013. The 129I concentrations were 1.0-1.8 × 107 atoms L-1 in the surface waters in the vicinity of 47°N 150°E-130°W North Pacific Ocean, Bering Sea, and Chukchi Sea (<74°N), which are equal to or lower than the 129I concentration level in surface water in the North Pacific Ocean before the F1NPP accident. The vertical profiles in the North Pacific were almost same as that observed in the western North Pacific before the F1NPP accident. The 129I distribution in seawater in the North Pacific to the Chukchi Sea revealed no significant increase of 129I concentration caused by the F1NPP accident. The 129I concentrations were 13-14 × 107 atoms L-1 in surface waters and 80 × 107 atoms L-1 at depths of 300 and 800 m in the Arctic Ocean.

Baseline Monitoring of the Western Arctic Ocean Estimates 20% of Canadian Basin Surface Waters Are Undersaturated with Respect to Aragonite

PubMed Central

Robbins, Lisa L.; Wynn, Jonathan G.; Lisle, John T.; Yates, Kimberly K.; Knorr, Paul O.; Byrne, Robert H.; Liu, Xuewu; Patsavas, Mark C.; Azetsu-Scott, Kumiko; Takahashi, Taro

2013-01-01

Marine surface waters are being acidified due to uptake of anthropogenic carbon dioxide, resulting in surface ocean areas of undersaturation with respect to carbonate minerals, including aragonite. In the Arctic Ocean, acidification is expected to occur at an accelerated rate with respect to the global oceans, but a paucity of baseline data has limited our understanding of the extent of Arctic undersaturation and of regional variations in rates and causes. The lack of data has also hindered refinement of models aimed at projecting future trends of ocean acidification. Here, based on more than 34,000 data records collected in 2010 and 2011, we establish a baseline of inorganic carbon data (pH, total alkalinity, dissolved inorganic carbon, partial pressure of carbon dioxide, and aragonite saturation index) for the western Arctic Ocean. This data set documents aragonite undersaturation in ∼20% of the surface waters of the combined Canada and Makarov basins, an area characterized by recent acceleration of sea ice loss. Conservative tracer studies using stable oxygen isotopic data from 307 sites show that while the entire surface of this area receives abundant freshwater from meteoric sources, freshwater from sea ice melt is most closely linked to the areas of carbonate mineral undersaturation. These data link the Arctic Ocean’s largest area of aragonite undersaturation to sea ice melt and atmospheric CO2 absorption in areas of low buffering capacity. Some relatively supersaturated areas can be linked to localized biological activity. Collectively, these observations can be used to project trends of ocean acidification in higher latitude marine surface waters where inorganic carbon chemistry is largely influenced by sea ice meltwater. PMID:24040074

A High-resolution Palaeomagnetic Secular Variation Record from the Chukchi Sea, Arctic Ocean for the Last 4200 Years

NASA Astrophysics Data System (ADS)

West, G.; O'Regan, M.; Jakobsson, M.; Nilsson, A.; Pearce, C.; Snowball, I.; Wiers, S.

2017-12-01

The lack of high-temporal resolution and well-dated palaeomagnetic records from the Arctic Ocean hinders our understanding of geomagnetic field behaviour in the region, and limits the applicability of these records in the development of accurate age models for Arctic Ocean sediments. We present a palaeomagnetic secular variation (PSV) record from a sediment core recovered from the Chukchi Sea, Arctic Ocean during the SWERUS-C3 Leg 2 Expedition. The 8.24-metre-long core was collected at 57 m water depth in the Herald Canyon (72.52° N 175.32° W), and extends to 4200 years BP based on 14 AMS 14C dates and a tephra layer associated with the 3.6 cal ka BP Aniakchak eruption. Palaeomagnetic measurements and magnetic analyses of discrete samples reveal stable characteristic remanent magnetisation directions, and a magnetic mineralogy dominated by magnetite. Centennial to millennial scale declination and inclination features, which correlate well to other Western Arctic records, can be readily identified. The relative palaeointensity record of the core matches well with spherical harmonic field model outputs of pfm9k (Nilsson et al., 2014) and CALS10k.2 (Constable et al. 2016) for the site location. Supported by a robust chronology, the presented high-resolution PSV record can potentially play a key role in constructing a well-dated master chronology for the region.

Mitigation implications of an ice-free summer in the Arctic Ocean

NASA Astrophysics Data System (ADS)

González-Eguino, Mikel; Neumann, Marc B.; Arto, Iñaki; Capellán-Perez, Iñigo; Faria, Sérgio H.

2017-01-01

The rapid loss of sea ice in the Arctic is one of the most striking manifestations of climate change. As sea ice melts, more open water is exposed to solar radiation, absorbing heat and generating a sea-ice-albedo feedback that reinforces Arctic warming. Recent studies stress the significance of this feedback mechanism and suggest that ice-free summer conditions in the Arctic Ocean may occur faster than previously expected, even under low-emissions pathways. Here we use an integrated assessment model to explore the implications of a potentially rapid sea-ice-loss process. We consider a scenario leading to a full month free of sea ice in September 2050, followed by three potential trajectories afterward: partial recovery, stabilization, and continued loss of sea ice. We analyze how these scenarios affect the efforts to keep global temperature increase below 2°C. Our results show that sea-ice melting in the Arctic requires more stringent mitigation efforts globally. We find that global CO2 emissions would need to reach zero levels 5-15 years earlier and that the carbon budget would need to be reduced by 20%-51% to offset this additional source of warming. The extra mitigation effort would imply an 18%-59% higher mitigation cost to society. Our results also show that to achieve the 1.5°C target in the presence of ice-free summers negative emissions would be needed. This study highlights the need for a better understanding of how the rapid changes observed in the Arctic may impact our society.

Toward an Arctic Strategy

DTIC Science & Technology

2009-02-01

Arctic Sea Ice Extent6 Reduced ice pack area translates to less reflected solar energy, which further accelerates the ongoing melting process . Light... process , creating a vicious cycle where melting ice causes the remaining ice to melt faster.7 Modelers previously agreed that the Arctic Ocean could be...freight ports stand to benefit by shipping through the Arctic region.10 For example, an ocean voyage from Yokohama, Japan, to Hamburg, Germany via the

Changes in Arctic Melt Season and Implications for Sea Ice Loss

NASA Technical Reports Server (NTRS)

Stroeve, J. C.; Markus, T.; Boisvert, L.; Miller, J.; Barrett, A.

2014-01-01

The Arctic-wide melt season has lengthened at a rate of 5 days dec-1 from 1979 to 2013, dominated by later autumn freeze-up within the Kara, Laptev, East Siberian, Chukchi and Beaufort seas between 6 and 11 days dec(exp -1). While melt onset trends are generally smaller, the timing of melt onset has a large influence on the total amount of solar energy absorbed during summer. The additional heat stored in the upper ocean of approximately 752MJ m(exp -2) during the last decade, increases sea surface temperatures by 0.5 to 1.5 C and largely explains the observed delays in autumn freeze-up within the Arctic Ocean's adjacent seas. Cumulative anomalies in total absorbed solar radiation from May through September for the most recent pentad locally exceed 300-400 MJ m(exp -2) in the Beaufort, Chukchi and East Siberian seas. This extra solar energy is equivalent to melting 0.97 to 1.3 m of ice during the summer.

Exploring Arctic history through scientific drilling

NASA Astrophysics Data System (ADS)

ODP Leg 151 Shipboard Scientific Party

During the brief Arctic summer of 1993, the Ocean Drilling Program's research vessel JOIDES Resolution recovered the first scientific drill cores from the eastern Arctic Ocean. Dodging rafts of pack ice shed from the Arctic ice cap, the science party sampled sediments north of 80°N latitude from the Yermak Plateau, as well as from sites in Fram Strait, the northeastern Greenland margin, and the Iceland Plateau (Figure 1).The sediments collected reveal the earliest history of the connection between the North Atlantic and Arctic Oceans through the Nordic Seas. The region between Greenland and Norway first formed a series of isolated basins, sometimes with restricted deep circulation, that eventually joined and allowed deep and surface Arctic Ocean water to invade the region. A record was also retrieved that shows major glaciation in the region began about 2.5 m.y.a.

Influence of Sea Ice on the Thermohaline Circulation in the Arctic-North Atlantic Ocean

NASA Technical Reports Server (NTRS)

Mauritzen, Cecilie; Haekkinen, Sirpa

1997-01-01

A fully prognostic coupled ocean-ice model is used to study the sensitivity of the overturning cell of the Arctic-North-Atlantic system to sea ice forcing. The strength of the thermohaline cell will be shown to depend on the amount of sea ice transported from the Arctic to the Greenland Sea and further to the subpolar gyre. The model produces a 2-3 Sv increase of the meridional circulation cell at 25N (at the simulation year 15) corresponding to a decrease of 800 cu km in the sea ice export from the Arctic. Previous modeling studies suggest that interannual and decadal variability in sea ice export of this magnitude is realistic, implying that sea ice induced variability in the overturning cell can reach 5-6 Sv from peak to peak.

The Role of Ocean and Atmospheric Heat Transport in the Arctic Amplification

NASA Astrophysics Data System (ADS)

Vargas Martes, R. M.; Kwon, Y. O.; Furey, H. H.

2017-12-01

Observational data and climate model projections have suggested that the Arctic region is warming around twice faster than the rest of the globe, which has been referred as the Arctic Amplification (AA). While the local feedbacks, e.g. sea ice-albedo feedback, are often suggested as the primary driver of AA by previous studies, the role of meridional heat transport by ocean and atmosphere is less clear. This study uses the Community Earth System Model version 1 Large Ensemble simulation (CESM1-LE) to seek deeper understanding of the role meridional oceanic and atmospheric heat transports play in AA. The simulation consists of 40 ensemble members with the same physics and external forcing using a single fully coupled climate model. Each ensemble member spans two time periods; the historical period from 1920 to 2005 using the Coupled Model Intercomparison Project Phase 5 (CMIP5) historical forcing and the future period from 2006 to 2100 using the CMIP5 Representative Concentration Pathways 8.5 (RCP8.5) scenario. Each of the ensemble members are initialized with slightly different air temperatures. As the CESM1-LE uses a single model unlike the CMIP5 multi-model ensemble, the internal variability and the externally forced components can be separated more clearly. The projections are calculated by comparing the period 2081-2100 relative to the time period 2001-2020. The CESM1-LE projects an AA of 2.5-2.8 times faster than the global average, which is within the range of those from the CMIP5 multi-model ensemble. However, the spread of AA from the CESM1-LE, which is attributed to the internal variability, is 2-3 times smaller than that of the CMIP5 ensemble, which may also include the inter-model differences. CESM1LE projects a decrease in the atmospheric heat transport into the Arctic and an increase in the oceanic heat transport. The atmospheric heat transport is further decomposed into moisture transport and dry static energy transport. Also, the oceanic heat

Numerical simulation of vertical transport and oxidation of methane in Arctic Ocean

NASA Astrophysics Data System (ADS)

Stepanenko, Victor; Iakovlev, Nikolai

2013-04-01

The high abundance of methane in shelf of East Siberian Arctic Seas (ESAS) has been a subject of a number of field studies (e.g. Shakhova et al., 2010). This experimental evidence provoked discussions on probable origins of that methane and possible feedbacks to modern climate change. For instance, the hypothesis of methane hydrates degradation under current ocean warming was tested recently in several modeling studies none of which supported this degradation to be significant feedback for climate change. Regardless the origin of methane the knowledge of its budget in the water column is important to link its bottom flux with emission to the atmosphere (and vice versa). It is frequently assumed that all methane released from a seabed of ESAS shelf reaches the atmosphere. When using ocean circulation models (Biastoch et al., 2011) this simplification is cancelled out but the vertical resolution of 3D models at the shelf (that is several tens meters deep) is not enough to accurately resolve turbulent transport of methane and other gases. Moreover, up the knowledge of authors none of the ocean models includes explicitly bubble transport of gases. These constrains motivate this study. In this study a high-resolution 1D single column ocean model is constructed to explicitly simulate the methane transport, oxidation and emission to the atmosphere. The model accounts for both vertical turbulent transport (using k-ɛ closure) and bubble transport of gases. The ground under the seabed is represented by multilayer heat and moisture transfer model, including methane hydrate evolution. It is forced by time series of atmospheric variables from NCEP reanalysis and horizontal advection terms taken from FEMAO-1 3D ocean model. The baseline simulation is performed for the period 1948-2011. The model is validated using temperature profiles measured at research vessels in ESAS. The annual cycle and multiyear variability of methane profiles in water are studied and compared to

Aerosol composition and sources in the Central Arctic Ocean during ASCOS

NASA Astrophysics Data System (ADS)

Chang, R. Y.-W.; Leck, C.; Graus, M.; Müller, M.; Paatero, J.; Burkhart, J. F.; Stohl, A.; Orr, L. H.; Hayden, K.; Li, S.-M.; Hansel, A.; Tjernström, M.; Leaitch, W. R.; Abbatt, J. P. D.

2011-05-01

Measurements of submicron aerosol chemical composition were made in the Central Arctic Ocean from 5 August to 8 September 2008 as a part of the Arctic Summer Cloud Ocean Study (ASCOS) using an aerosol mass spectrometer (AMS). The median levels of sulphate and organics for the entire study were 0.042 and 0.046 μg m-3, respectively. Positive matrix factorisation was performed on the entire mass spectral time series and this enabled marine biogenic and continental sources of particles to be separated. These factors accounted for 33 % and 36 % of the sampled ambient aerosol mass, respectively, and they were both predominantly composed of sulphate, with 47 % of the sulphate apportioned to marine biogenic sources and 48 % to continental sources, by mass. Within the marine biogenic factor, the ratio of methane sulphonate to sulphate was 0.25 ± 0.02, consistent with values reported in the literature. The organic component of the continental factor was more oxidised than that of the marine biogenic factor, suggesting that it was more processed and had been present longer in the atmosphere than the organics in the marine biogenic factor. The remaining ambient aerosol mass was apportioned to an organic-rich factor that could have arisen from a combination of marine and continental sources.

230Th and 231Pa: Tracers for Deep Water Circulation and Particle Fluxes in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Valk, O.; Rutgers van der Loeff, M.; Puigcorbe Lacueva, V.; Paffrath, R.; Gdaniec, S.

2016-02-01

230Th and 231Pa data from the central Arctic Ocean is very limited. 230Th and 231Pa are produced at a constant rate in the water column by radioactive decay of Uranium isotopes (234U and 235U respectively) (e.g. Anderson et al., 1983). They are both particle reactive and are scavenged on settling particles. As 230Th is more particle reactive than 231Pa, their distribution in the water column and activity ratio give us information about particle fluxes and circulation patterns and -intensities (Henderson et al., 1999; Scholten et al., 2001). The Arctic Ocean is an almost landlocked ocean with limited connections to the Atlantic and Pacific and a high input of river water. About 10 % of the global river run-off is delivered to the Arctic Ocean. Due to climate change the Arctic Ocean will undergo dramatic changes in sea ice cover and supply of fresh water, while increasing coastal erosion will cause an increased input of terrestrial material (Peterson et al., 2002). This will influence the biogeochemical cycling and transport of carbon, nutrients and trace elements (IPCC, 2007). We expect that the distribution of 230Th and 231Pa will reflect changes in particle fluxes and shelf-basin exchange (Roy-Barman, 2009). We will present the first results of 230Th and 231Pa, in combination with on board measured particulate 234Th, collected during the 2015 Polarstern section (GEOTRACES section GN04 2015) through the Nansen, Amundsen, and Makarov Basins. Anderson, R. F., et al. (1983). EPSL 62: 7-23. Henderson, G. M., et al. (1999). DSR I 46: 1861-1893. IPCC, 2007. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S. et al.]. Cambridge University Press. Peterson, B. J., et al. (2002). Science 298: 2171-2173. Roy-Barman, M. (2009). Biogeosciences 6: 3091-3107. Scholten, J. C., et al. (2001). DSR II 48: 2383-2408.

A Synthesis of Light Absorption Properties of the Arctic Ocean: Application to Semi-analytical Estimates of Dissolved Organic Carbon Concentrations from Space

NASA Technical Reports Server (NTRS)

Matsuoka, A.; Babin, M.; Doxaran, D.; Hooker, S. B.; Mitchell, B. G.; Belanger, S.; Bricaud, A.

2014-01-01

The light absorption coefficients of particulate and dissolved materials are the main factors determining the light propagation of the visible part of the spectrum and are, thus, important for developing ocean color algorithms. While these absorption properties have recently been documented by a few studies for the Arctic Ocean [e.g., Matsuoka et al., 2007, 2011; Ben Mustapha et al., 2012], the datasets used in the literature were sparse and individually insufficient to draw a general view of the basin-wide spatial and temporal variations in absorption. To achieve such a task, we built a large absorption database at the pan-Arctic scale by pooling the majority of published datasets and merging new datasets. Our results showed that the total non-water absorption coefficients measured in the Eastern Arctic Ocean (EAO; Siberian side) are significantly higher 74 than in the Western Arctic Ocean (WAO; North American side). This higher absorption is explained 75 by higher concentration of colored dissolved organic matter (CDOM) in watersheds on the Siberian 76 side, which contains a large amount of dissolved organic carbon (DOC) compared to waters off 77 North America. In contrast, the relationship between the phytoplankton absorption (a()) and chlorophyll a (chl a) concentration in the EAO was not significantly different from that in the WAO. Because our semi-analytical CDOM absorption algorithm is based on chl a-specific a() values [Matsuoka et al., 2013], this result indirectly suggests that CDOM absorption can be appropriately erived not only for the WAO but also for the EAO using ocean color data. Derived CDOM absorption values were reasonable compared to in situ measurements. By combining this algorithm with empirical DOC versus CDOM relationships, a semi-analytical algorithm for estimating DOC concentrations for coastal waters at the Pan-Arctic scale is presented and applied to satellite ocean color data.

Effects of sea ice cover on satellite-detected primary production in the Arctic Ocean

PubMed Central

Lee, Zhongping; Mitchell, B. Greg; Nevison, Cynthia D.

2016-01-01

The influence of decreasing Arctic sea ice on net primary production (NPP) in the Arctic Ocean has been considered in multiple publications but is not well constrained owing to the potentially large errors in satellite algorithms. In particular, the Arctic Ocean is rich in coloured dissolved organic matter (CDOM) that interferes in the detection of chlorophyll a concentration of the standard algorithm, which is the primary input to NPP models. We used the quasi-analytic algorithm (Lee et al. 2002 Appl. Opti. 41, 5755−5772. (doi:10.1364/AO.41.005755)) that separates absorption by phytoplankton from absorption by CDOM and detrital matter. We merged satellite data from multiple satellite sensors and created a 19 year time series (1997–2015) of NPP. During this period, both the estimated annual total and the summer monthly maximum pan-Arctic NPP increased by about 47%. Positive monthly anomalies in NPP are highly correlated with positive anomalies in open water area during the summer months. Following the earlier ice retreat, the start of the high-productivity season has become earlier, e.g. at a mean rate of −3.0 d yr−1 in the northern Barents Sea, and the length of the high-productivity period has increased from 15 days in 1998 to 62 days in 2015. While in some areas, the termination of the productive season has been extended, owing to delayed ice formation, the termination has also become earlier in other areas, likely owing to limited nutrients. PMID:27881759

Effects of sea ice cover on satellite-detected primary production in the Arctic Ocean.

PubMed

Kahru, Mati; Lee, Zhongping; Mitchell, B Greg; Nevison, Cynthia D

2016-11-01

The influence of decreasing Arctic sea ice on net primary production (NPP) in the Arctic Ocean has been considered in multiple publications but is not well constrained owing to the potentially large errors in satellite algorithms. In particular, the Arctic Ocean is rich in coloured dissolved organic matter (CDOM) that interferes in the detection of chlorophyll a concentration of the standard algorithm, which is the primary input to NPP models. We used the quasi-analytic algorithm (Lee et al 2002 Appl. Opti. 41, 5755-5772. (doi:10.1364/AO.41.005755)) that separates absorption by phytoplankton from absorption by CDOM and detrital matter. We merged satellite data from multiple satellite sensors and created a 19 year time series (1997-2015) of NPP. During this period, both the estimated annual total and the summer monthly maximum pan-Arctic NPP increased by about 47%. Positive monthly anomalies in NPP are highly correlated with positive anomalies in open water area during the summer months. Following the earlier ice retreat, the start of the high-productivity season has become earlier, e.g. at a mean rate of -3.0 d yr -1 in the northern Barents Sea, and the length of the high-productivity period has increased from 15 days in 1998 to 62 days in 2015. While in some areas, the termination of the productive season has been extended, owing to delayed ice formation, the termination has also become earlier in other areas, likely owing to limited nutrients. © 2016 The Author(s).

Pan-Arctic Distribution of Bioavailable Dissolved Organic Matter and Linkages With Productivity in Ocean Margins

NASA Astrophysics Data System (ADS)

Shen, Yuan; Benner, Ronald; Kaiser, Karl; Fichot, Cédric G.; Whitledge, Terry E.

2018-02-01

Rapid environmental changes in the Arctic Ocean affect plankton productivity and the bioavailability of dissolved organic matter (DOM) that supports microbial food webs. We report concentrations of dissolved organic carbon (DOC) and yields of amino acids (indicators of labile DOM) in surface waters across major Arctic margins. Concentrations of DOC and bioavailability of DOM showed large pan-Arctic variability that corresponded to varying hydrological conditions and ecosystem productivity, respectively. Widespread hot spots of labile DOM were observed over productive inflow shelves (Chukchi and Barents Seas), in contrast to oligotrophic interior margins (Kara, Laptev, East Siberian, and Beaufort Seas). Amino acid yields in outflow gateways (Canadian Archipelago and Baffin Bay) indicated the prevalence of semilabile DOM in sea ice covered regions and sporadic production of labile DOM in ice-free waters. Comparing these observations with surface circulation patterns indicated varying shelf subsidies of bioavailable DOM to Arctic deep basins.

Origin of ice-rafted debris: Pleistocene paleoceanography in the western Arctic Ocean

NASA Astrophysics Data System (ADS)

Bischof, Jens; Clark, David L.; Vincent, Jean-Serge

1996-12-01

The composition of Pleistocene ice-rafted debris (IRD) >250 µm was analyzed quantitatively by grain counting in five sediment cores from the western central Arctic Ocean and compared with the composition of till clasts from NW Canada in order to determine the dropstone origin and to reconstruct the Pleistocene ice driftways and surface currents. The IRD composition alternates repeatedly between carbonate- and quartz-dominated assemblages, along with metamorphic and igneous rocks, clastic rocks, and some chert. The highest quartz content is found on the Alpha Ridge, while carbonate percentages are highest on the Northwind Ridge (NWR) and the Chukchi Cap. The source for the carbonates is the area around Banks and Victoria Islands and parts of northern Canada. Quartz most likely originated from the central Queen Elizabeth Islands. IRD on the southeastern Alpha Ridge is dominated by mafic crystalline rocks from northern Ellesmere Island and northern Greenland. At least six major glacial intervals are identified within the last 1 million years, during which icebergs drifted toward the west in the Beaufort Sea, straight northward in the central Arctic Ocean, and northeastward on the SE Alpha Ridge.

A propagating freshwater mode in the Arctic Ocean with multidecadal time scale

NASA Astrophysics Data System (ADS)

Schmith, Torben; Malskær Olsen, Steffen; Margrethe Ringgaard, Ida

2017-04-01

We apply Principal Oscillatory Pattern analysis to the Arctic Ocean fresh water content as simulated in a 500 year long control run with constant preindustrial forcing with the EC-Earth global climate model. Two modes emerge from this analysis. One mode is a standing mode with decadal time scale describing accumulation and release of fresh water in the Beaufort Gyre, known in the literature as the Beaufort Gyre flywheel. In addition, we identify a propagating mode with a time scale around 80 years, propagating along the rim of the Canadian Basin. This mode has maximum variability of the fresh water content in the Transpolar Drift and represents the bulk of the total variability of the fresh water content in the Arctic Ocean and also projects on the fresh water through the Fram Strait. Therefore, potentially, it can introduce a multidecadal variability to the Atlantic meridional overturning circulation. We will discuss the physical origin of this propagating mode. This include planetary-scale internal Rossby waves with multidecadal time scale, due to the slow variation of the Coriolis parameter at these high latitudes, as well as topographic steering of these Rossby waves.

Collaborative Project. Understanding the effects of tides and eddies on the ocean dynamics, sea ice cover and decadal/centennial climate prediction using the Regional Arctic Climate Model (RACM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hutchings, Jennifer; Joseph, Renu

2013-09-14

The goal of this project is to develop an eddy resolving ocean model (POP) with tides coupled to a sea ice model (CICE) within the Regional Arctic System Model (RASM) to investigate the importance of ocean tides and mesoscale eddies in arctic climate simulations and quantify biases associated with these processes and how their relative contribution may improve decadal to centennial arctic climate predictions. Ocean, sea ice and coupled arctic climate response to these small scale processes will be evaluated with regard to their influence on mass, momentum and property exchange between oceans, shelf-basin, ice-ocean, and ocean-atmosphere. The project willmore » facilitate the future routine inclusion of polar tides and eddies in Earth System Models when computing power allows. As such, the proposed research addresses the science in support of the BER’s Climate and Environmental Sciences Division Long Term Measure as it will improve the ocean and sea ice model components as well as the fully coupled RASM and Community Earth System Model (CESM) and it will make them more accurate and computationally efficient.« less

Spatial and temporal scales of sea ice protists and phytoplankton distribution from the gateway Fram Strait into the Central Arctic Ocean

NASA Astrophysics Data System (ADS)

Peeken, I.; Hardge, K.; Krumpen, T.; Metfies, K.; Nöthig, E. M.; Rabe, B.; von Appen, W. J.; Vernet, M.

2016-02-01

The Arctic Ocean is currently one of the key regions where the effect of climate change is most pronounced. Sea ice is an important interface in this region by representing a unique habitat for many organisms. Massive reduction of sea ice thickness and extent, which have been recorded over the last twenty years, is anticipated to cause large cascading changes in the entire Arctic ecosystem. Most sea ice is formed on the Eurasian shelves and transported via the Transpolardrift to the western Fram Strait and out of the Arctic Ocean with the cold East Greenland Current (EGC). Warm Atlantic water enters the Arctic Ocean with the West Spitsbergen Current (WSC) via eastern Fram Strait. Here, we focus on the spatial spreading of protists from the Atlantic water masses, and their occurrences over the deep basins of the Central Arctic and the relationship amongst them in water and sea ice. Communities were analyzed by using pigments, flow cytometer and ARISA fingerprints during several cruises with the RV Polarstern to the Fram Strait, the Greenland Sea and the Central Arctic Ocean. By comparing these data sets we are able to demonstrate that the origin of the studied sea ice floes is more important for the biodiversity found in the sea ice communities then the respective underlying water mass. In contrast, biodiversity in the water column is mainly governed by the occurring water masses and the presence or absence of sea ice. However, overall the development of standing stocks in both biomes was governed by the availability of nutrients. To get a temporal perspective of the recent results, the study will be embedded in a long-term data set of phytoplankton biomass obtained during several cruises over the last twenty years.

An early to mid-Pleistocene deep Arctic Ocean ostracode fauna with North Atlantic affinities

USGS Publications Warehouse

DeNinno, Lauren H.; Cronin, Thomas M.; Rodriquez-Lazaro, J.; Brenner, Alec R.

2015-01-01

An early to middle Pleistocene ostracode fauna was discovered in sediment core P1-93-AR-23 (P23, 76.95°N, 155.07°W) from 951 meter water depth from the Northwind Ridge, western Arctic Ocean. Piston core P23 yielded more than 30,000 specimens and a total of about 30 species. Several early to mid-Pleistocene species in the genera Krithe,Echinocythereis, Pterygocythereis, and Arcacythere are now extinct in the Arctic and show taxonomic affinities to North Atlantic Ocean species. Our results suggest that there was a major ostracode faunal turnover during the global climate transitions known as the Mid-Pleistocene Transition (MPT, ~ 1.2 to 0.7 Ma) and the Mid-Brunhes Event (MBE, ~ 400 ka) reflecting the development of perennial sea ice during interglacial periods and large ice shelves during glacial periods over the last 400,000 years.

Flux and age of dissolved organic carbon exported to the Arctic Ocean: A carbon isotopic study of the five largest arctic rivers

USGS Publications Warehouse

Raymond, P.A.; McClelland, J.W.; Holmes, R.M.; Zhulidov, A.V.; Mull, K.; Peterson, B.J.; Striegl, Robert G.; Aiken, G.R.; Gurtovaya, T.Y.

2007-01-01

The export and Δ14C-age of dissolved organic carbon (DOC) was determined for the Yenisey, Lena, Ob', Mackenzie, and Yukon rivers for 2004–2005. Concentrations of DOC elevate significantly with increasing discharge in these rivers, causing approximately 60% of the annual export to occur during a 2-month period following spring ice breakup. We present a total annual flux from the five rivers of ∼16 teragrams (Tg), and conservatively estimate that the total input of DOC to the Arctic Ocean is 25–36 Tg, which is ∼5–20% greater than previous fluxes. These fluxes are also ∼2.5× greater than temperate rivers with similar watershed sizes and water discharge. Δ14C-DOC shows a clear relationship with hydrology. A small pool of DOC slightly depleted in Δ14C is exported with base flow. The large pool exported with spring thaw is enriched in Δ14C with respect to current-day atmospheric Δ14C-CO2 values. A simple model predicts that ∼50% of DOC exported during the arctic spring thaw is 1–5 years old, ∼25% is 6–10 years in age, and 15% is 11–20 years old. The dominant spring melt period, a historically undersampled period, exports a large amount of young and presumably semilabile DOC to the Arctic Ocean.

Multinational Experiment 7. Maritime Security Region: The Arctic

DTIC Science & Technology

2013-07-08

Russia. Marine Resources The Arctic Ocean is home to countless species from microscopic plankton to gigantic whales . Large-scale commercial...Arctic is a circumpolar region that encompasses both marine and land masses and includes the Arctic Ocean and its seas that cover more than 30...and does not rise on the day of the winter solstice. The Arctic Ocean is the world’s smallest and shallowest, with an average depth of roughly a

The great 2012 Arctic Ocean summer cyclone enhanced biological productivity on the shelves

PubMed Central

Zhang, Jinlun; Ashjian, Carin; Campbell, Robert; Hill, Victoria; Spitz, Yvette H; Steele, Michael

2014-01-01

[1] A coupled biophysical model is used to examine the impact of the great Arctic cyclone of early August 2012 on the marine planktonic ecosystem in the Pacific sector of the Arctic Ocean (PSA). Model results indicate that the cyclone influences the marine planktonic ecosystem by enhancing productivity on the shelves of the Chukchi, East Siberian, and Laptev seas during the storm. Although the cyclone's passage in the PSA lasted only a few days, the simulated biological effects on the shelves last 1 month or longer. At some locations on the shelves, primary productivity (PP) increases by up to 90% and phytoplankton biomass by up to 40% in the wake of the cyclone. The increase in zooplankton biomass is up to 18% on 31 August and remains 10% on 15 September, more than 1 month after the storm. In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass. The biological gain on the shelves and loss in the central PSA are linked to two factors. (1) The cyclone enhances mixing in the upper ocean, which increases nutrient availability in the surface waters of the shelves; enhanced mixing in the central PSA does not increase productivity because nutrients there are mostly depleted through summer draw down by the time of the cyclone's passage. (2) The cyclone also induces divergence, resulting from the cyclone's low-pressure system that drives cyclonic sea ice and upper ocean circulation, which transports more plankton biomass onto the shelves from the central PSA. The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone. Because the gain on the shelves is offset by the loss in the central PSA, the average increase over the entire PSA is moderate and lasts only about 10 days. The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing

The great 2012 Arctic Ocean summer cyclone enhanced biological productivity on the shelves.

PubMed

Zhang, Jinlun; Ashjian, Carin; Campbell, Robert; Hill, Victoria; Spitz, Yvette H; Steele, Michael

2014-01-01

[1] A coupled biophysical model is used to examine the impact of the great Arctic cyclone of early August 2012 on the marine planktonic ecosystem in the Pacific sector of the Arctic Ocean (PSA). Model results indicate that the cyclone influences the marine planktonic ecosystem by enhancing productivity on the shelves of the Chukchi, East Siberian, and Laptev seas during the storm. Although the cyclone's passage in the PSA lasted only a few days, the simulated biological effects on the shelves last 1 month or longer. At some locations on the shelves, primary productivity (PP) increases by up to 90% and phytoplankton biomass by up to 40% in the wake of the cyclone. The increase in zooplankton biomass is up to 18% on 31 August and remains 10% on 15 September, more than 1 month after the storm. In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass. The biological gain on the shelves and loss in the central PSA are linked to two factors. (1) The cyclone enhances mixing in the upper ocean, which increases nutrient availability in the surface waters of the shelves; enhanced mixing in the central PSA does not increase productivity because nutrients there are mostly depleted through summer draw down by the time of the cyclone's passage. (2) The cyclone also induces divergence, resulting from the cyclone's low-pressure system that drives cyclonic sea ice and upper ocean circulation, which transports more plankton biomass onto the shelves from the central PSA. The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone. Because the gain on the shelves is offset by the loss in the central PSA, the average increase over the entire PSA is moderate and lasts only about 10 days. The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing

Observations of Recent Arctic Sea Ice Volume Loss and Its Impact on Ocean-Atmosphere Energy Exchange and Ice Production

NASA Technical Reports Server (NTRS)

Kurtz, N. T.; Markus, T.; Farrell, S. L.; Worthen, D. L.; Boisvert, L. N.

2011-01-01

Using recently developed techniques we estimate snow and sea ice thickness distributions for the Arctic basin through the combination of freeboard data from the Ice, Cloud, and land Elevation Satellite (ICESat) and a snow depth model. These data are used with meteorological data and a thermodynamic sea ice model to calculate ocean-atmosphere heat exchange and ice volume production during the 2003-2008 fall and winter seasons. The calculated heat fluxes and ice growth rates are in agreement with previous observations over multiyear ice. In this study, we calculate heat fluxes and ice growth rates for the full distribution of ice thicknesses covering the Arctic basin and determine the impact of ice thickness change on the calculated values. Thinning of the sea ice is observed which greatly increases the 2005-2007 fall period ocean-atmosphere heat fluxes compared to those observed in 2003. Although there was also a decline in sea ice thickness for the winter periods, the winter time heat flux was found to be less impacted by the observed changes in ice thickness. A large increase in the net Arctic ocean-atmosphere heat output is also observed in the fall periods due to changes in the areal coverage of sea ice. The anomalously low sea ice coverage in 2007 led to a net ocean-atmosphere heat output approximately 3 times greater than was observed in previous years and suggests that sea ice losses are now playing a role in increasing surface air temperatures in the Arctic.

Atmosphere-Ice-Ocean-Ecosystem Processes in a Thinner Arctic Sea Ice Regime: The Norwegian Young Sea ICE (N-ICE2015) Expedition

NASA Astrophysics Data System (ADS)

Granskog, Mats A.; Fer, Ilker; Rinke, Annette; Steen, Harald

2018-03-01

Arctic sea ice has been in rapid decline the last decade and the Norwegian young sea ICE (N-ICE2015) expedition sought to investigate key processes in a thin Arctic sea ice regime, with emphasis on atmosphere-snow-ice-ocean dynamics and sea ice associated ecosystem. The main findings from a half-year long campaign are collected into this special section spanning the Journal of Geophysical Research: Atmospheres, Journal of Geophysical Research: Oceans, and Journal of Geophysical Research: Biogeosciences and provide a basis for a better understanding of processes in a thin sea ice regime in the high Arctic. All data from the campaign are made freely available to the research community.

Reconstruction of Plio-Pleistocene paleoceanographic conditions in the western Arctic Ocean based on a Northwind Ridge sediment record.

NASA Astrophysics Data System (ADS)

Dipre, G.; Polyak, L.; Ortiz, J. D.; Oti, E.; Kuznetsov, A.

2017-12-01

The rapid loss of sea ice in the Arctic Ocean is expected to result in major climatic and hydrographic changes, some of which are already being observed. To better understand these changes, it is necessary to investigate paleoclimatic conditions during times when the Arctic had similarly reduced sea-ice cover. The Pliocene to early Pleistocene period ( 1-5 Ma) may represent the best analog, as the modern Arctic geography had developed with the opening of the Bering Strait (ca. 5-6 Ma), but major Northern Hemisphere glaciations other than Greenland had not fully begun. Here we present an investigation of sediment core HLY0503-03JPC from top of the Northwind Ridge, western Arctic Ocean. This sedimentary record contains uniquely preserved calcareous microfossils through the early Pleistocene according to strontium isotope ages. Based on extrapolation of these ages, the record extends to at least the late Pliocene. We evaluate paleo-sea ice conditions using benthic foraminifera assemblages, similar to a prior study of a nearby core (Polyak et al., 2013), along with physical (sediment optical properties, density, grain size) and chemical (XRF, δ18O, δ13C) proxies to reconstruct paleo-circulation and sediment transport processes. Based on these proxies, the record exhibits a distinct tripartite stratigraphic division. The top unit, recovering the middle to late Quaternary, shows sedimentary impacts of major glaciations and mostly perennial sea ice conditions. The second unit, dated to the early Pleistocene, indicates reduced glacial inputs, mostly seasonal sea ice, and potentially intensified current conditions. Finally, preliminary results for the oldest unit, presumably representing the late Pliocene, suggest a more acidic ocean characterized by low, if any, sea ice presence and increased current activity. As similar conditions (acidification, storminess) are starting to be observed in the changing modern environment, this third unit may provide especially valuable

Baseline monitoring of the western Arctic Ocean estimates 20% of the Canadian Basin surface waters are undersaturated with respect to aragonite

USGS Publications Warehouse

Robbins, Lisa L.; Wynn, Jonathan G.; Lisle, John T.; Yates, Kimberly K.; Knorr, Paul O.; Byrne, Robert H.; Liu, Xuewu; Patsavas, Mark C.; Azetsu-Scott, Kumiko; Takahashi, Taro

2013-01-01

Marine surface waters are being acidified due to uptake of anthropogenic carbon dioxide, resulting in surface ocean areas of undersaturation with respect to carbonate minerals, including aragonite. In the Arctic Ocean, acidification is expected to occur at an accelerated rate with respect to the global oceans, but a paucity of baseline data has limited our understanding of the extent of Arctic undersaturation and of regional variations in rates and causes. The lack of data has also hindered refinement of models aimed at projecting future trends of ocean acidification. Here, based on more than 34,000 data records collected in 2010 and 2011, we establish a baseline of inorganic carbon data (pH, total alkalinity, dissolved inorganic carbon, partial pressure of carbon dioxide, and aragonite saturation index) for the western Arctic Ocean. This data set documents aragonite undersaturation in ~20% of the surface waters of the combined Canada and Makarov basins, an area characterized by recent acceleration of sea ice loss. Conservative tracer studies using stable oxygen isotopic data from 307 sites show that while the entire surface of this area receives abundant freshwater from meteoric sources, freshwater from sea ice melt is most closely linked to the areas of carbonate mineral undersaturation. These data link the Arctic Ocean’s largest area of aragonite undersaturation to sea ice melt and atmospheric CO2 absorption in areas of low buffering capacity. Some relatively supersaturated areas can be linked to localized biological activity. Collectively, these observations can be used to project trends of ocean acidification in higher latitude marine surface waters where inorganic carbon chemistry is largely influenced by sea ice meltwater.

High-resolution sub-bottom seismic and sediment core records from the Chukchi Abyssal Plain reveal Quaternary glaciation impacts on the western Arctic Ocean

NASA Astrophysics Data System (ADS)

Joe, Y. J.; Seokhoon, Y.; Nam, S. I.; Polyak, L.; Niessen, F.

2017-12-01

For regional context of the Quaternary history of Arctic marine glaciations, such as glacial events in northern North America and on the Siberian and Chukchi margins, we used CHIRP sub-bottom profiles (SBP) along with sediment cores, including a 14-m long piston core ARA06-04JPC taken from the Chukchi abyssal plain during the RV Araon expedition in 2015. Based on core correlation with earlier developed Arctic Ocean stratigraphies using distribution of various sedimentary proxies, core 04JPC is estimated to extend to at least Marine Isotope Stage 13 (>0.5 Ma). The stratigraphy developed for SBP lines from the Chukchi abyssal plain to surrounding slopes can be divided into four major seismostratigraphic units (SSU 1-4). SBP records from the abyssal plain show well preserved stratification, whereas on the surrounding slopes this pattern is disrupted by lens-shaped, acoustically transparent sedimentary bodies interpreted as glaciogenic debris flow deposits. Based on the integration of sediment physical property and SBP data, we conclude that these debris flows were generated during several ice-sheet grounding events on the Chukchi and East Siberian margins, including adjacent ridges and plateaus, during the middle to late Quaternary.

Wide Distribution of Closely Related, Antibiotic-Producing Arthrobacter Strains throughout the Arctic Ocean

PubMed Central

Wietz, Matthias; Månsson, Maria; Bowman, Jeff S.; Blom, Nikolaj; Ng, Yin

2012-01-01

We isolated 16 antibiotic-producing bacterial strains throughout the central Arctic Ocean, including seven Arthrobacter spp. with almost identical 16S rRNA gene sequences. These strains were numerically rare, as revealed using 454 pyrosequencing libraries. Arthrobacter spp. produced arthrobacilins A to C under different culture conditions, but other, unidentified compounds likely contributed to their antibiotic activity. PMID:22247128

Numerical Simulation of Salinity and Dissolved Oxygen at Perdido Bay and Adjacent Coastal Ocean

EPA Science Inventory

Environmental Fluid Dynamic Code (EFDC), a numerical estuarine and coastal ocean circulation hydrodynamic model, was used to simulate the distribution of the salinity, temperature, nutrients and dissolved oxygen (DO) in Perdido Bay and adjacent Gulf of Mexico. External forcing fa...

Arctic Ocean sea ice drift origin derived from artificial radionuclides.

PubMed

Cámara-Mor, P; Masqué, P; Garcia-Orellana, J; Cochran, J K; Mas, J L; Chamizo, E; Hanfland, C

2010-07-15

Since the 1950s, nuclear weapon testing and releases from the nuclear industry have introduced anthropogenic radionuclides into the sea, and in many instances their ultimate fate are the bottom sediments. The Arctic Ocean is one of the most polluted in this respect, because, in addition to global fallout, it is impacted by regional fallout from nuclear weapon testing, and indirectly by releases from nuclear reprocessing facilities and nuclear accidents. Sea-ice formed in the shallow continental shelves incorporate sediments with variable concentrations of anthropogenic radionuclides that are transported through the Arctic Ocean and are finally released in the melting areas. In this work, we present the results of anthropogenic radionuclide analyses of sea-ice sediments (SIS) collected on five cruises from different Arctic regions and combine them with a database including prior measurements of these radionuclides in SIS. The distribution of (137)Cs and (239,240)Pu activities and the (240)Pu/(239)Pu atom ratio in SIS showed geographical differences, in agreement with the two main sea ice drift patterns derived from the mean field of sea-ice motion, the Transpolar Drift and Beaufort Gyre, with the Fram Strait as the main ablation area. A direct comparison of data measured in SIS samples against those reported for the potential source regions permits identification of the regions from which sea ice incorporates sediments. The (240)Pu/(239)Pu atom ratio in SIS may be used to discern the origin of sea ice from the Kara-Laptev Sea and the Alaskan shelf. However, if the (240)Pu/(239)Pu atom ratio is similar to global fallout, it does not provide a unique diagnostic indicator of the source area, and in such cases, the source of SIS can be constrained with a combination of the (137)Cs and (239,240)Pu activities. Therefore, these anthropogenic radionuclides can be used in many instances to determine the geographical source area of sea-ice. Copyright 2010 Elsevier B.V. All

Operationalising a social-ecological system perspective on the Arctic Ocean.

PubMed

Crépin, Anne-Sophie; Gren, Åsa; Engström, Gustav; Ospina, Daniel

2017-12-01

We propose a framework to support management that builds on a social-ecological system perspective on the Arctic Ocean. We illustrate the framework's application for two policy-relevant scenarios of climate-driven change, picturing a shift in zooplankton composition and alternatively a crab invasion. We analyse archetypical system dynamics between the socio-economic, the natural, and the governance systems in these scenarios. Our holistic approach can help managers identify looming problems arising from complex system interactions and prioritise among problems and solutions, even when available data are limited.

A synthesis of light absorption properties of the Pan-Arctic Ocean: application to semi-analytical estimates of dissolved organic carbon concentrations from space

NASA Astrophysics Data System (ADS)

Matsuoka, A.; Babin, M.; Doxaran, D.; Hooker, S. B.; Mitchell, B. G.; Bélanger, S.; Bricaud, A.

2013-11-01

The light absorption coefficients of particulate and dissolved materials are the main factors determining the light propagation of the visible part of the spectrum and are, thus, important for developing ocean color algorithms. While these absorption properties have recently been documented by a few studies for the Arctic Ocean (e.g., Matsuoka et al., 2007, 2011; Ben Mustapha et al., 2012), the datasets used in the literature were sparse and individually insufficient to draw a general view of the basin-wide spatial and temporal variations in absorption. To achieve such a task, we built a large absorption database at the pan-Arctic scale by pooling the majority of published datasets and merging new datasets. Our results showed that the total non-water absorption coefficients measured in the Eastern Arctic Ocean (EAO; Siberian side) are significantly higher than in the Western Arctic Ocean (WAO; North American side). This higher absorption is explained by higher concentration of colored dissolved organic matter (CDOM) in watersheds on the Siberian side, which contains a large amount of dissolved organic carbon (DOC) compared to waters off North America. In contrast, the relationship between the phytoplankton absorption (aφ(λ)) and chlorophyll a (chl a) concentration in the EAO was not significantly different from that in the WAO. Because our semi-analytical CDOM absorption algorithm is based on chl a-specific aφ(λ) values (Matsuoka et al., 2013), this result indirectly suggests that CDOM absorption can be appropriately derived not only for the WAO but also for the EAO using ocean color data. Derived CDOM absorption values were reasonable compared to in situ measurements. By combining this algorithm with empirical DOC vs. CDOM relationships, a semi-analytical algorithm for estimating DOC concentrations for coastal waters at the Pan-Arctic scale is presented and applied to satellite ocean color data.

Increasing transnational sea-ice exchange in a changing Arctic Ocean

NASA Astrophysics Data System (ADS)

Newton, Robert; Pfirman, Stephanie; Tremblay, Bruno; DeRepentigny, Patricia

2017-06-01

The changing Arctic sea-ice cover is likely to impact the trans-border exchange of sea ice between the exclusive economic zones (EEZs) of the Arctic nations, affecting the risk of ice-rafted contamination. We apply the Lagrangian Ice Tracking System (LITS) to identify sea-ice formation events and track sea ice to its melt locations. Most ice (52%) melts within 100 km of where it is formed; ca. 21% escapes from its EEZ. Thus, most contaminants will be released within an ice parcel's originating EEZ, while material carried by over 1 00,000 km2 of ice—an area larger than France and Germany combined—will be released to other nations' waters. Between the periods 1988-1999 and 2000-2014, sea-ice formation increased by ˜17% (roughly 6 million km2 vs. 5 million km2 annually). Melting peaks earlier; freeze-up begins later; and the central Arctic Ocean is more prominent in both formation and melt in the later period. The total area of ice transported between EEZs increased, while transit times decreased: for example, Russian ice reached melt locations in other nations' EEZs an average of 46% faster while North American ice reached destinations in Eurasian waters an average of 37% faster. Increased trans-border exchange is mainly a result of increased speed (˜14% per decade), allowing first-year ice to escape the summer melt front, even as the front extends further north. Increased trans-border exchange over shorter times is bringing the EEZs of the Arctic nations closer together, which should be taken into account in policy development—including establishment of marine-protected areas.

Dissolved methane in the Beaufort Sea and the Arctic Ocean, 1992-2009; sources and atmospheric flux

USGS Publications Warehouse

Lorenson, Thomas D.; Greinert, Jens; Coffin, Richard B.

2016-01-01

Methane concentration and isotopic composition was measured in ice-covered and ice-free waters of the Arctic Ocean during eleven surveys spanning the years of 1992-1995 and 2009. During ice-free periods, methane flux from the Beaufort shelf varies from 0.14 to 0.43 mg CH4 m-2 day-1. Maximum fluxes from localized areas of high methane concentration are up to 1.52 mg CH4 m-2 day-1. Seasonal buildup of methane under ice can produce short-term fluxes of methane from the Beaufort shelf that varies from 0.28 to 1.01 to mg CH4 m-2 day-1. Scaled-up estimates of minimum methane flux from the Beaufort Sea and pan-Arctic shelf for both ice-free and ice-covered periods range from 0.02 Tg CH4 yr-1 and 0.30 Tg CH4 yr-1 respectively to maximum fluxes of 0.18 Tg CH4 yr-1 and 2.2 Tg CH4 yr-1 respectively. A methane flux of 0.36 Tg CH4 yr-1from the deep Arctic Ocean was estimated using data from 1993-94. The flux can be as much as 2.35 Tg CH4 yr-1 estimated from maximum methane concentrations and wind speeds of 12 m/s, representing only 0.42% of the annual atmospheric methane budget of ~560 Tg CH4 yr-1. There were no significant changes in methane fluxes during the time period of this study. Microbial methane sources predominate with minor influxes from thermogenic methane offshore Prudhoe Bay and the Mackenzie River delta and may include methane from gas hydrate. Methane oxidation is locally important on the shelf and is a methane sink in the deep Arctic Ocean.

A modelling study of the influence of anomalous wind forcing over the Barents Sea on the Atlantic water flow to the Arctic Ocean in the period 1979-2004

NASA Astrophysics Data System (ADS)

Marciniak, Jakub; Schlichtholz, Pawel; Maslowski, Wieslaw

2016-04-01

Arctic climate system is influenced by oceanic heat transport with the Atlantic water (AW) streaming towards the Arctic Ocean in two branches, through the deep Fram Strait and the shallow Barents Sea. In Fram Strait, the AW submerges below the Polar surface water and then flows cyclonically along the margin of the Arctic Ocean as a subsurface water mass in the Arctic Slope Current. In contrast to the Fram Strait branch, which is the major source of heat for the Arctic Ocean, most of the heat influx to the Barents Sea through the Barents Sea opening (BSO) is passed to the atmosphere. Only cold remnants of AW outflow to the Arctic Ocean through the northeastern gate of the Barents Sea. Some AW entering the Barents Sea recirculates westward, contributing to an outflow from the Barents Sea through the BSO along the shelf slope south of Bear Island, in the Bear Island Slope Current. Even though the two-branched AW flow toward the Arctic Ocean has been known for more than a century, little is known about co-variability of heat fluxes in the two branches, its mechanisms and climatic implications. Recent studies indicate that the Bear Island Slope Current may play a role in this co-variability. Here, co-variability of the flow through the BSO and Fram Strait is investigated using a pan-Arctic coupled ice-ocean hindcast model run for the period 1979-2004 and forced with daily atmospheric data from the ECMWF. Significant wintertime co-variability between the volume transport in the Bear Island and Arctic slope currents and its link to wind forcing over the Barents Sea is confirmed. It is found that the volume transports in these currents are, however, not correlated in the annual mean and that the wintertime co-variability of these currents has no immediate effect on either the net heat flux through the BSO or the net heat flux divergence in the Barents Sea. It is shown that the main climatic effect of wind forcing over the northern Barents Sea shelf is to induce temperature

Evolution of biogeochemical cycling of phosphorus during 45~50 Ma revealed by sequential extraction analysis of IODP Expedition 302 cores from the Arctic Ocean

NASA Astrophysics Data System (ADS)

Hashimoto, S.; Yamaguchi, K. E.; Takahashi, K.

2012-12-01

The modern Arctic Ocean plays crucial roles in controlling global climate system with the driving force of global thermohaline circulation through the formation of dense deep water and high albedo due to the presence of perennial sea-ice. However, the Arctic sea-ice has not always existed in the past. Integrated Ocean Drilling Program (IODP) Expedition 302 Arctic Coring Expedition (ACEX) has clarified that global warming (water temperature: ca. 14~16○C) during 48~49 Ma Azolla Event induced the loss of sea-ice and desalination of surface ocean, and that sea-ice formed again some million years later (45 Ma). In the Arctic Ocean, warming and cooling events repeated over and over (e.g., Brinkhuis et al., 2006; Moran et al., 2006; März et al., 2010). Large variations in the extent of thermohaline circulation through time often caused stagnation of seawater and appearance of anaerobic environment where hydrogen sulfide was produced by bacterial sulfate reduction. Ogawa et al. (2009) confirmed occurrence of framboidal pyrite in the ACEX sediments, and suggested that the Arctic Ocean at the time was anoxic, analogous to the modern Black Sea, mainly based on sulfur isotope analysis. To further clarify the variations in the nutrient status of the Arctic Ocean, we focus on the geochemical cycle of phosphorus. We performed sequential extraction analysis of sedimentary phosphorus in the ACEX sediments, using the method that we improvped based on the original SEDEX method by Ruttenberg (1992) and Schenau et al. (2000). In our method, phosphorus fractions are divided into five forms; (1) absorbed P, (2) Feoxide-P, (4) carbonate fluorapatite (CFAP) + CaCO3-P + hydroxylapatite (HAP), (4) detrital P, and (5) organic P. Schenau et al. (2000) divided the (3) fraction into non-biological CFAP and biological HAP and CaCO3-P. When the Arctic Ocean was closed and in its warming period, the water mass was most likely stratified and an anaerobic condition would have prevailed where

Can we constrain postglacial sedimentation in the western Arctic Ocean by ramped pyrolysis 14C? A case study from the Chukchi-Alaskan margin.

NASA Astrophysics Data System (ADS)

Suzuki, K.; Yamamoto, M.; Rosenheim, B. E.; Omori, T.; Polyak, L.; Nam, S. I.

2017-12-01

The Arctic Ocean underwent dramatic climate changes in the past. Variations in sea-ice extent and ocean current system in the Arctic cause changes in surface albedo and deep water formation, which have global climatic implications. However, Arctic paleoceanographic studies are lagging behind the other oceans due largely to chronostratigraphic difficulties. One of the reasons for this is a scant presence of material suitable for 14C dating in large areas of the Arctic seafloor. To enable improved age constraints for sediments impoverished in datable material, we apply ramped pyrolysis 14C method (Ramped PyrOx 14C, Rosenheim et al., 2008) to sedimentary records from the Chukchi-Alaska margin recovering Holocene to late-glacial deposits. Samples were divided into five fraction products by gradual heating sedimentary organic carbon from ambient laboratory temperature to 1000°C. The thermographs show a trimodal pattern of organic matter decomposition over temperature, and we consider that CO2 generated at the lowest temperature range was derived from autochthonous organic carbon contemporaneous with sediment deposition, similar to studies in the Antarctic margin and elsewhere. For verification of results, some of the samples treated for ramped pyrolysis 14C were taken from intervals dated earlier by AMS 14C using bivalve mollusks. Ultimately, our results allow a new appraisal of deglacial to Holocene deposition at the Chukchi-Alaska margin with potential to be applied to other regions of the Arctic Ocean.

Diminishing sea ice in the western Arctic Ocean

USGS Publications Warehouse

Stone, R.S.; Belchansky, G.I.; Drobot, Sheldon; Douglas, David C.; Levinson, D.H.; Waple, A.M.

2004-01-01

Since the advent of satellite passive microwave radiometry (1978), variations in sea ice extent and concentration have been carefully monitored from space. An estimated 7.4% decrease in sea ice extent has occurred in the last 25 yr (Johannessen et al. 2004), with recent record minima (e.g., Maslanik et al. 1999; Serreze et al. 2003) accounting for much of the decline. Comparisons between the time series of Arctic sea ice melt dynamics and snowmelt dates at the NOAA–CMDL Barrow Observatory (BRW) reveal intriguing correlations.Melt-onset dates over sea ice (Drobot and Anderson 2001) were cross correlated with the melt-date time series from BRW, and a prominent region of high correlation between snowmelt onset over sea ice and the BRW record of melt dates was approximately aligned with the climatological center of the Beaufort Sea Anticyclone (BSA). The BSA induces anticyclonic ice motion in the region, effectively forcing the Beaufort gyre. A weak gyre caused by a breakdown of the BSA diminishes transport of multiyear ice into this region (Drobot and Maslanik 2003). Similarly, the annual snow cycle at BRW varies with the position and intensity of the BSA (Stone et al. 2002, their Fig. 6). Thus, variations in the BSA appear to have far-reaching effects on the annual accumulation and subsequent melt of snow over a large region of the western Arctic.A dramatic increase in melt season duration (Belchansky et al. 2004) was also observed within the same region of high correlation between onset of melt over the ice pack and snowmelt at BRW (Fig. 5.7). By inference, this suggests linkages between factors that modulate the annual cycle of snow on land and processes that influence melting of snow and ice in the western Arctic Ocean.

Reconstructing Holocene Summer Sea-Ice Conditions in the Central and Western Arctic Ocean: Morphological Variations and Stable Isotope Composition of Neogloboquadrina pachyderma

NASA Astrophysics Data System (ADS)

Asahi, H.; Nam, S. I.; Stein, R. H.; Mackensen, A.; Son, Y. J.

2017-12-01

The usability of planktic foraminiferal census data in Arctic paleoceanography is limited by the predominance of Neogloboquadrina pachyderma (sinistral). Though a potential usability of their morphological variation has been suggested by recent studies, its application is restricted to the central part of the Arctic Ocean. Here we present their regional distribution, using 80 surface sediment samples from the central and the western Arctic Ocean. Among seven morphological variations encountered, distinct presence of "large-sized" N. pachyderma morphotypes at the summer sea-ice edge in the western Arctic demonstrates its strong potential as sea-ice distribution indicator. Based on their regional patterns, we further developed planktic foraminifer (PF)-based transfer functions (TFs) to reconstruct summer surface-water temperature, salinity and sea-ice concentration in the western and central Arctic. The comparison of sea-ice reconstructions by PF-based TF to other pre-existed approaches showed their recognizable advantages/disadvantages: the PF-based approach in the nearby/within heavily ice-covered region, the dinocyst-based approach in the extensively seasonal ice retreat region, and the IP25-based approach with overall reflection over a wide range of sea-ice coverage, which is likely attributed to their (a) taphonomical information-loss, (b) different seasonal production patterns or combination of both. The application of these TFs on a sediment core from Northwind Ridge suggests general warming, freshening, and sea-ice reduction after 6.0 ka. This generally agrees with PF stable isotope records and sea-ice reconstructions from dinocyst-based TF at proximal locations, indicating that the sea-ice behavior at the Northwind Ridge is notably different from the IP25-based sea-ice reconstructions reported from elsewhere in the Arctic Ocean. Lack of regional coverage of PF-based reconstructions hampers further discussion whether the observed inconsistency is simply

CMIP5-based global wave climate projections including the entire Arctic Ocean

NASA Astrophysics Data System (ADS)

Casas-Prat, M.; Wang, X. L.; Swart, N.

2018-03-01

This study presents simulations of the global ocean wave climate corresponding to the surface winds and sea ice concentrations as simulated by five CMIP5 (Coupled Model Intercomparison Project Phase 5) climate models for the historical (1979-2005) and RCP8.5 scenario future (2081-2100) periods. To tackle the numerical complexities associated with the inclusion of the North Pole, the WAVEWATCH III (WW3) wave model was used with a customized unstructured Spherical Multi-Cell grid of ∼100 km offshore and ∼50 km along coastlines. The climate model simulated wind and sea ice data, and the corresponding WW3 simulated wave data, were evaluated against reanalysis and hindcast data. The results show that all the five sets of wave simulations projected lower waves in the North Atlantic, corresponding to decreased surface wind speeds there in the warmer climate. The selected CMIP5 models also consistently projected an increase in the surface wind speed in the Southern Hemisphere (SH) mid-high latitudes, which translates in an increase in the WW3 simulated significant wave height (Hs) there. The higher waves are accompanied with increased peak wave period and increased wave age in the East Pacific and Indian Oceans, and a significant counterclockwise rotation in the mean wave direction in the Southern Oceans. The latter is caused by more intense waves from the SH traveling equatorward and developing into swells. Future wave climate in the Arctic Ocean in summer is projected to be predominantly of mixed sea states, with the climatological mean of September maximum Hs ranging mostly 3-4 m. The new waves approaching Arctic coasts will be less fetch-limited as ice retreats since a predominantly southwards mean wave direction is projected in the surrounding seas.

Dissolved organic matter (DOM) in pore water of Arctic Ocean sediments: linking DOM molecular composition with microbial community structure

NASA Astrophysics Data System (ADS)

Rossel, P. E.; Bienhold, C.; Boetius, A.; Dittmar, T.

2016-02-01

Marine organic matter (OM) that sinks from surface waters to the seafloor is the energy and carbon source for benthic communities. These communities produce dissolved organic matter (DOM) in the process of remineralization, enriching the sediment porewater with fresh DOM compounds. In the Arctic Ocean, primary production is limited by nutrients and light and is thus strongly influenced by sea ice cover. Ice cover is expected to further decrease due to global warming, which may have important consequences for primary production and the quantity and quality of OM exported to the seafloor. This study focused on: 1) the molecular composition of the DOM in sediment pore waters of the deep Eurasian Arctic basins, 2) whether there is any relation between Arctic Ocean ice cover and DOM composition and 3) whether the DOM composition correlates with microbial community structure. Molecular data, obtained via 15 Tesla Fourier transform ion cyclotron resonance mass spectrometry, were statistically correlated with environmental parameters. The productive ice margin stations showed higher abundances of molecular formulae of peptides, unsaturated aliphatics and saturated fatty acids. This molecular trend is indicative of fresh OM and phytodetritus deposition, compared to the northernmost, ice-covered stations which had stronger aromatic signals. Benthic bacterial community structure, as assessed with the fingerprinting method ARISA, was significantly correlated with DOM molecular composition. Further analyses using Illumina next-generation sequencing will enable the taxonomic identification of specific bacterial groups and their interdependence with DOM compounds. This study contributes to the understanding of the coupling between Arctic Ocean productivity and its depositional regime, and provides first insights into potential links between microbial community structure and DOM molecular composition in Arctic sediments

Airborne surveys in the Arctic and Antarctic for geophysics, sea-ice thickness, and CryoSat validation

NASA Astrophysics Data System (ADS)

Forsberg, R.; Olesen, A. V.; Hvidegaard, S.; Skourup, H.

2010-12-01

Airborne laser and radar measurements over the Greenland ice sheet, Svalbard, and adjacent parts of the Arctic Ocean have been carried out by DTU-Space in a number of recent Danish/Greenlandic and European project campaigns, with the purpose to monitor ice sheet and sea-ice changes, support of Greenland societal needs (oil exploration and hydropower), and support of CryoSat pre-launch calibration and validation campaigns. The Arctic campaigns have been done using a Twin-Otter aircraft, carrying laser scanners and various radars. Since 2009 a new program of long-range gravity and magnetic surveys have been initiated using a Basler DC3 aircraft for large-scale surveys in the Arctic Ocean and Antarctica, with the 2010 cooperative Danish-Argentinean-Chilean-US ICEGRAV survey of the Antarctic Peninsula additionally including a UTIG 60 MHz ice-penetrating radar. In the paper we outline the recent and upcoming airborne survey activities, outline the usefulness of the airborne data for satellite validation (CryoSat and GOCE), and give examples of measurements and comparisons to satellite and in-situ data.

Ship accessibility predictions for the Arctic Ocean based on IPCC CO2 emission scenarios

NASA Astrophysics Data System (ADS)

Oh, Jai-Ho; Woo, Sumin; Yang, Sin-Il

2017-02-01

Changes in the extent of Arctic sea ice, which have resulted from climate change, offer new opportunities to use the Northern Sea Route (NSR) and Northwest Passage (NWP) for shipping. However, choosing to navigate the Arctic Ocean remains challenging due to the limited accessibility of ships and the balance between economic gain and potential risk. As a result, more precise and detailed information on both weather and sea ice change in the Arctic are required. In this study, a high-resolution global AGCM was used to provide detailed information on the extent and thickness of Arctic sea ice. For this simulation, we have simulated the AMIP-type simulation for the present-day climate during 31 years from 1979 to 2009 with observed SST and Sea Ice concentration. For the future climate projection, we have performed the historical climate during 1979-2005 and subsequently the future climate projection during 2010-2099 with mean of four CMIP5 models due to the two Representative Concentration Pathway scenarios (RCP 8.5 and RCP 4.5). First, the AMIP-type simulation was evaluated by comparison with observations from the Hadley Centre sea-ice and Sea Surface Temperature (HadlSST) dataset. The model reflects the maximum (in March) and minimum (in September) sea ice extent and annual cycle. Based on this validation, the future sea ice extents show the decreasing trend for both the maximum and minimum seasons and RCP 8.5 shows more sharply decreasing patterns of sea ice than RCP 4.5. Under both scenarios, ships classified as Polar Class (PC) 3 and Open-Water (OW) were predicted to have the largest and smallest number of ship-accessible days (in any given year) for the NSR and NWP, respectively. Based on the RCP 8.5 scenario, the projections suggest that after 2070, PC3 and PC6 vessels will have year-round access across to the Arctic Ocean. In contrast, OW vessels will continue to have a seasonal handicap, inhibiting their ability to pass through the NSR and NWP.

Sea Ice Pressure Ridge Height Distributions for the Arctic Ocean in Winter, Just Prior to Melt

NASA Astrophysics Data System (ADS)

Duncan, K.; Farrell, S. L.; Richter-Menge, J.; Hutchings, J.; Dominguez, R.; Connor, L. N.

2016-12-01

Pressure ridges are one of the most dominant morphological features of the Arctic sea ice pack. An impediment to navigation, pressure ridges are also of climatological interest since they impact the mass, energy and momentum transfer budgets for the Arctic Ocean. Understanding the regional and seasonal distributions of ridge sail heights, and their variability, is important for quantifying total sea ice mass, and for improved treatment of sea ice dynamics in high-resolution numerical models. Observations of sail heights from airborne and ship-based platforms have been documented in previous studies, however studies with both high spatial and temporal resolution, across multiple regions of the Arctic, are only recently possible with the advent of dedicated airborne surveys of the Arctic Ocean. In this study we present results from the high-resolution Digital Mapping System (DMS), flown as part of NASA's Operation IceBridge missions. We use DMS imagery to calculate ridge sail heights, derived from the shadows they cast combined with the solar elevation angle and the known pixel size of each image. Our analyses describe sea ice conditions at the end of winter, during the months of March and April, over a period spanning seven years, from 2010 to 2016. The high spatial resolution (0.1m) and temporal extent (seven years) of the DMS data set provides, for the first time, the full sail-height distributions of both first-year and multi-year sea ice. We present the inter-annual variability in sail height distributions for both the Central Arctic and the Beaufort and Chukchi Seas. We validate our results via comparison with spatially coincident high-resolution SAR imagery and airborne laser altimeter elevations.

Patterns of Seasonal Heat Uptake and Release Over the Arctic Ocean Between 1979-2016

NASA Astrophysics Data System (ADS)

Helmberger, M. N.; Serreze, M. C.

2017-12-01

As the Arctic Ocean loses its sea ice cover, there is a stronger oceanic heat gain from the surface fluxes throughout the spring and summer; ultimately meaning that there is more energy to transfer out of the ocean to the atmosphere and outer space in the autumn and winter. Recent work has shown that the increased oceanic heat content at the end of summer in turn delays autumn ice growth, with implications for marine shipping and other economic activities. Some of the autumn and winter heat loss to the atmosphere is represented by evaporation, which increases the atmospheric water vapor content, and there is growing evidence that this is contributing to increases in regional precipitation. However, depending on patterns of seasonal sea ice retreat and weather conditions, the spring-summer heat uptake and autumn-winter heat loss can be highly variable from year to year and regionally. Here, we examine how the seasonality in upper ocean heat uptake and release has evolved over the past 37 years and the relationships between this seasonal heat gain and loss and the evolution of sea ice cover. We determine which regions have seen the largest increases in total seasonal heat uptake and how variable this uptake can be. Has the timing at which the Arctic Ocean (either as a whole or by region) transitions from an atmospheric energy sink to an atmospheric energy source (or from a source to a sink) appreciably changed? What changes have been observed in the seasonal rates of seasonal heat uptake and release? To begin answering these questions, use is made of surface fluxes from the ERA-Interim reanalysis and satellite-derived sea ice extent spanning the period 1979 through the present. Results from ERA-Interim will be compared to those from other reanalyses and satellite-derived flux estimates.

Under-ice turbulent microstructure and upper ocean vertical fluxes in the Makarov and Eurasian basins, Arctic Ocean, during late spring and late summer / autumn in 2015

NASA Astrophysics Data System (ADS)

Rabe, Benjamin; Janout, Markus; Graupner, Rainer; Hoelemann, Jens; Hampe, Hendrik; Hoppmann, Mario; Horn, Myriel; Juhls, Bennet; Korhonen, Meri; Nikolopoulos, Anna; Pisarev, Sergey; Randelhoff, Achim; Savy, Jean-Philippe; Villacieros Robineau, Nicolas

2017-04-01

The Arctic Ocean is generally assumed to be fairly quiescent when compared to many other oceans. The sea-ice cover, a strong halocline and a shallow, cold mixed-layer prevents much of the ocean to be affected by atmospheric conditions and properties of the ocean mixed-layer. In turn, the mixed-layer and the sea-ice is largely isolated from the warm layer of Atlantic origin below by the lower halocline. Yet, the content of heat, freshwater and biologically important nutrients differs strongly between these different layers. Hence, it is crucial to be able to estimate vertical fluxes of salt, heat and nutrients to understand variability in the upper Arctic Ocean and the sea-ice, including the ecosystem. Yet, it is difficult to obtain direct flux measurements, and estimates are sparse. We present several sets of under-ice turbulent microstructure profiles in the Eurasian and Makarov Basin of the Arctic Ocean from two expeditions, in 2015. These cover melt during late spring north of Svalbard and freeze-up during late summer / autumn across the Eurasian and Makarov basins. Our results are presented against a background of the anomalously warm atmospheric conditions during summer 2015 followed by unusually low temperatures in September. 4 - 24 h averages of the measurements generally show elevated dissipation rates at the base of the mixed-layer. We found highest levels of dissipation near the Eurasian continental slope and smaller peaks in the profiles where Bering Sea Summer Water (sBSW) lead to additional stratification within the upper halocline in the Makarov Basin. The elevated levels of dissipation associated with sBSW and the base of the mixed-layer were associated with the relatively low levels of vertical eddy diffusivity. We discuss these findings in the light of the anomalous conditions in the upper ocean, sea-ice and the atmosphere during 2015 and present estimates of vertical fluxes of heat, salt and other dissolved substances measured in water samples.

Depositional History of the Western Amundsen Basin, Arctic Ocean, and Implications for Neogene Climate and Oceanographic Conditions

NASA Astrophysics Data System (ADS)

Hopper, J. R.; Castro, C. F.; Knutz, P. C.; Funck, T.

2017-12-01

Seismic reflection data collected in the western Amundsen Basin as part of the Law of the Sea program for the Kingdom of Denmark show a uniform and continuous cover of sediments over oceanic basement. An interpretation of seismic facies units shows that the depositional history of the basin reflects changing tectonic, climatic, and oceanographic conditions throughout the Cenozoic. In this contribution, the Miocene to present history is summarized. Two distinct changes in the depositional environment are proposed, first in response to the development of a deep water connection between the Arctic and North Atlantic, and the second in response to the onset of perennial sea ice cover in the Arctic. In the early to mid-Miocene, a buildup of contourite deposits indicates a distinct change in sedimentation that is particularly well developed near the flank of the Lomonosov Ridge. It is suggested that this is a response to the opening of the Fram Strait and the establishment of geostrophic bottom currents that flowed from the Laptev Sea towards Greenland. These deposits are overlain by a seismic facies unit characterized by buried channels and erosional features. These include prominent basinward levee systems that suggest a channel morphology maintained by overbank deposition of muddy sediments carried by suspension currents periodically spilling over the channel pathway. These deposits indicate a change to a much higher energy environment that is proposed to be a response to brine formation associated with the onset of perennial sea ice cover in the Arctic Ocean. This interpretation implies that the development of extensive sea ice cover results in a significant change in the energy environment of the ocean that is reflected in the depositional and erosional patterns observed. The lack of similar high energy erosional features and the presence of contourite deposits throughout most of the Miocene may indicate the Arctic Ocean was relatively ice-free until the very latest

Remote sensing estimation of terrestrially derived colored dissolved organic matterinput to the Arctic Ocean

NASA Astrophysics Data System (ADS)

Li, J.; Yu, Q.; Tian, Y. Q.

2017-12-01

The DOC flux from land to the Arctic Ocean has remarkable implication on the carbon cycle, biogeochemical & ecological processes in the Arctic. This lateral carbon flux is required to be monitored with high spatial & temporal resolution. However, the current studies in the Arctic regions were obstructed by the factors of the low spatial coverages. The remote sensing could provide an alternative bio-optical approach to field sampling for DOC dynamics monitoring through the observation of the colored dissolved organic matter (CDOM). The DOC and CDOM were found highly correlated based on the analysis of the field sampling data from the Arctic-GRO. These provide the solid foundation of the remote sensing observation. In this study, six major Arctic Rivers (Yukon, Kolyma, Lena, Mackenzie, Ob', Yenisey) were selected to derive the CDOM dynamics along four years. Our newly developed SBOP algorithm was applied to the large Landsat-8 OLI image data (nearly 100 images) for getting the high spatial resolution results. The SBOP algorithm is the first approach developing for the Shallow Water Bio-optical properties estimation. The CDOM absorption derived from the satellite images were verified with the field sampling results with high accuracy (R2 = 0.87). The distinct CDOM dynamics were found in different Rivers. The CDOM absorptions were found highly related to the hydrological activities and the terrestrially environmental dynamics. Our study helps to build the reliable system for studying the carbon cycle at Arctic regions.

Levoglucosan indicates high levels of biomass burning aerosols over oceans from the Arctic to Antarctic

PubMed Central

Hu, Qi-Hou; Xie, Zhou-Qing; Wang, Xin-Ming; Kang, Hui; Zhang, Pengfei

2013-01-01

Biomass burning is known to affect air quality, global carbon cycle, and climate. However, the extent to which biomass burning gases/aerosols are present on a global scale, especially in the marine atmosphere, is poorly understood. Here we report the molecular tracer levoglucosan concentrations in marine air from the Arctic Ocean through the North and South Pacific Ocean to Antarctica during burning season. Levoglucosan was found to be present in all regions at ng/m3 levels with the highest atmospheric loadings present in the mid-latitudes (30°–60° N and S), intermediate loadings in the Arctic, and lowest loadings in the Antarctic and equatorial latitudes. As a whole, levoglucosan concentrations in the Southern Hemisphere were comparable to those in the Northern Hemisphere. Biomass burning has a significant impact on atmospheric Hg and water-soluble organic carbon (WSOC) from pole-to-pole, with more contribution to WSOC in the Northern Hemisphere than in the Southern Hemisphere. PMID:24176935

Levoglucosan indicates high levels of biomass burning aerosols over oceans from the Arctic to Antarctic.

PubMed

Hu, Qi-Hou; Xie, Zhou-Qing; Wang, Xin-Ming; Kang, Hui; Zhang, Pengfei

2013-11-01

Biomass burning is known to affect air quality, global carbon cycle, and climate. However, the extent to which biomass burning gases/aerosols are present on a global scale, especially in the marine atmosphere, is poorly understood. Here we report the molecular tracer levoglucosan concentrations in marine air from the Arctic Ocean through the North and South Pacific Ocean to Antarctica during burning season. Levoglucosan was found to be present in all regions at ng/m(3) levels with the highest atmospheric loadings present in the mid-latitudes (30°-60° N and S), intermediate loadings in the Arctic, and lowest loadings in the Antarctic and equatorial latitudes. As a whole, levoglucosan concentrations in the Southern Hemisphere were comparable to those in the Northern Hemisphere. Biomass burning has a significant impact on atmospheric Hg and water-soluble organic carbon (WSOC) from pole-to-pole, with more contribution to WSOC in the Northern Hemisphere than in the Southern Hemisphere.

Greater role for Atlantic inflows on sea-ice loss in the Eurasian Basin of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Polyakov, Igor V.; Pnyushkov, Andrey V.; Alkire, Matthew B.; Ashik, Igor M.; Baumann, Till M.; Carmack, Eddy C.; Goszczko, Ilona; Guthrie, John; Ivanov, Vladimir V.; Kanzow, Torsten; Krishfield, Richard; Kwok, Ronald; Sundfjord, Arild; Morison, James; Rember, Robert; Yulin, Alexander

2017-04-01

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 the 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.

Investigating the role of wind in generating surface currents over the slope area of the Laptev Sea, Arctic Ocean

NASA Astrophysics Data System (ADS)

Patteson, R. N.

2017-12-01

Mixing mechanisms of the Arctic Ocean have profound impacts on sea ice, global ocean dynamics, and arctic communities. This project used a two-year long time series of ocean current velocities collected from eight moorings located on the Eurasian basin, as well as ERA-interim wind data, to compare and assess relationships between current and wind velocities at different depths. Determining the strength of these correlations will further scientific understanding of the degree to which wind influences mixing, with implications for heat flux, diffusion, and sea ice changes. Using statistical analysis, I calculated whether a significant relationship between wind velocity and ocean currents existed beginning at the surface level ( 50m) .The final correlation values, ranging from R = 0.11 to R = 0.28, indicated a weak relationship between wind velocity and ocean currents at the surface for all eight mooring sites. The results for the surface depth imply that correlation likely decreases with increasing depths, and thus further testing of deeper depth levels was unnecessary. This finding suggests that there is another dominant factor at play in the ocean; we postulate that topography exerts a significant influence on subsurface mixing. This study highlights the need for further research of the different mechanisms and their importance in influencing the dynamic structure of the ocean.

Pathways of PFOA to the Arctic: variabilities and contributions of oceanic currents and atmospheric transport and chemistry sources

NASA Astrophysics Data System (ADS)

Stemmler, I.; Lammel, G.

2010-10-01

Perfluorooctanoic acid (PFOA) and other perfluorinated compounds are industrial chemicals in use for decades which resist degradation in the environment and seem to accumulate in polar regions. Transport of PFOA was modeled using a spatially resolved global multicompartment model including fully coupled three-dimensional ocean and atmosphere general circulation models, and two-dimensional top soil, vegetation surfaces, and sea ice compartments. In addition to primary emissions, the formation of PFOA in the atmosphere from degradation of 8:2 fluorotelomer alcohol was included as a PFOA source. Oceanic transport, delivered 14.8±5.0 (8-23) t a-1 to the Arctic, strongly influenced by changes in water transport, which determined its interannual variability. This pathway constituted the dominant source of PFOA to the Arctic. Formation of PFOA in the atmosphere led to episodic transport events (timescale of days) into the Arctic with small spatial extent. Deposition in the polar region was found to be dominated by wet deposition over land, and shows maxima in boreal winter. The total atmospheric deposition of PFOA in the Arctic in the 1990s was ≈1 t a-1, much higher than previously estimated, and is dominated by primary emissions rather than secondary formation.

Pathways of PFOA to the Arctic: variabilities and contributions of oceanic currents and atmospheric transport and chemistry sources

NASA Astrophysics Data System (ADS)

Stemmler, I.; Lammel, G.

2010-05-01

Perfluorooctanoic acid (PFOA) and other perfluorinated compounds are industrial chemicals in use since decades which resist degradation in the environment and seem to accumulate in polar regions. Transport of PFOA was modeled using a spatially resolved global multicompartment model including fully coupled three-dimensional ocean and atmosphere general circulation models, and two-dimensional top soil, vegetation surfaces, and sea ice compartments. In addition to primary emissions, the formation of PFOA in the atmosphere from degradation of 8:2 fluorotelomer alcohol was included as a PFOA source. Oceanic transport, delivered 14.8±5.0 (8-23) t a-1 to the Arctic, strongly influenced by changes in water transport, which determined its interannual variability. This pathway constituted the dominant source of PFOA to the Arctic. Formation of PFOA in the atmosphere lead to episodic transport events (timescale of days) into the Arctic with small spatial extent. Deposition in the polar region was found to be dominated by wet deposition over land, and shows maxima in boreal winter. The total atmospheric deposition of PFOA in the Arctic in the 1990s was ≍1 t a-1, much higher than previously estimated, and is dominated by primary emissions rather than secondarily formed.

Planktic foraminifer census data from Northwind Ridge Core 5, Arctic Ocean

USGS Publications Warehouse

Foley, Kevin M.; Poore, Richard Z.

1991-01-01

The U.S. Geological Survey recovered 9 piston cores from the Northwind Ridge in the Canada Basin of the Arctic Ocean from a cruise of the USCGC Polar Star during 1988. Preliminary analysis of the cores suggests sediments deposited on Northwind Ridge preserve a detailed record of glacial and interglacial cycles for the last few hundred-thousand to one million years. This report includes quantitative data on foraminifers and selected sediment size-fraction data in samples from Northwind Ridge core PI-88AR P5.

Impacts of Siberian biomass burning on organic aerosols over the North Pacific Ocean and the Arctic: primary and secondary organic tracers.

PubMed

Ding, Xiang; Wang, Xinming; Xie, Zhouqing; Zhang, Zhou; Sun, Liguang

2013-04-02

During the 2003 Chinese Arctic Research Expedition (CHINARE2003) from the Bohai Sea to the high Arctic (37°N-80°N), filter-based particle samples were collected and analyzed for tracers of primary and secondary organic aerosols (SOA) as well as water-soluble organic carbon (WSOC). Biomass burning (BB) tracer levoglucosan had comparatively much higher summertime average levels (476 ± 367 pg/m(3)) during our cruise due to the influence of intense forest fires then in Siberia. On the basis of 5-day back trajectories, samples with air masses passing through Siberia had organic tracers 1.3-4.4 times of those with air masses transporting only over the oceans, suggesting substantial contribution of continental emissions to organic aerosols in the marine atmosphere. SOA tracers from anthropogenic aromatics were negligible or not detected, while those from biogenic terpenenoids were ubiquitously observed with the sum of SOA tracers from isoprene (623 ± 414 pg/m(3)) 1 order of magnitude higher than that from monoterpenes (63 ± 49 pg/m(3)). 2-Methylglyceric acid as a product of isoprene oxidation under high-NOx conditions was dominant among SOA tracers, implying that these BSOA tracers were not formed over the oceans but mainly transported from the adjacent Siberia where a high-NOx environment could be induced by intense forest fires. The carbon fractions shared by biogenic SOA tracers and levoglucosan in WSOC in our ocean samples were 1-2 orders of magnitude lower than those previously reported in continental samples, BB emissions or chamber simulation samples, largely due to the chemical evolution of organic tracers during transport. As a result of the much faster decline in levels of organic tracers than that of WSOC during transport, the trace-based approach, which could well reconstruct WSOC using biogenic SOA and BB tracers for continental samples, only explained ∼4% of measured WSOC during our expedition if the same tracer-WSOC or tracer-SOC relationships were

Quaternary Sea-ice history in the Arctic Ocean based on a new Ostracode sea-ice proxy

USGS Publications Warehouse

Cronin, T. M.; Gemery, L.; Briggs, W.M.; Jakobsson, M.; Polyak, L.; Brouwers, E.M.

2010-01-01

Paleo-sea-ice history in the Arctic Ocean was reconstructed using the sea-ice dwelling ostracode Acetabulastoma arcticum from late Quaternary sediments from the Mendeleyev, Lomonosov, and Gakkel Ridges, the Morris Jesup Rise and the Yermak Plateau. Results suggest intermittently high levels of perennial sea ice in the central Arctic Ocean during Marine Isotope Stage (MIS) 3 (25-45 ka), minimal sea ice during the last deglacial (16-11 ka) and early Holocene thermal maximum (11-5 ka) and increasing sea ice during the mid-to-late Holocene (5-0 ka). Sediment core records from the Iceland and Rockall Plateaus show that perennial sea ice existed in these regions only during glacial intervals MIS 2, 4, and 6. These results show that sea ice exhibits complex temporal and spatial variability during different climatic regimes and that the development of modern perennial sea ice may be a relatively recent phenomenon. ?? 2010.

Quaternary ostracode and foraminiferal biostratigraphy and paleoceanography in the western Arctic Ocean

USGS Publications Warehouse

Cronin, Thomas M.; DeNinno, Lauren H.; Polyak, L.V.; Caverly, Emma K.; Poore, Richard; Brenner, Alec R.; Rodriguez-Lazaro, J.; Marzen, R.E.

2014-01-01

The stratigraphic distributions of ostracodes and selected calcareous benthic and planktic foraminiferal species were studied in sediment cores from ~ 700 to 2700 m water depth on the Northwind, Mendeleev, and Lomonosov Ridges in the western Arctic Ocean. Microfaunal records in most cores cover mid- to late Quaternary sediments deposited in the last ~ 600 ka, with one record covering the last ~ 1.5 Ma. Results show a progressive faunal turnover during the mid-Pleistocene transition (MPT, ~ 1.2 to 0.7 Ma) and around the mid-Brunhes event (MBE, ~ 0.4 Ma) reflecting major changes in Arctic Ocean temperature, circulation and sea-ice cover. The observed MPT shift is characterized by the extinction of species that today inhabit the sea-ice free subpolar North Atlantic and/or seasonally sea-ice free Nordic Seas (Echinocythereis sp., Rockalliacf. enigmatica, Krithe cf. aquilonia, Pterygocythereis vannieuwenhuisei). After a very warm interglacial during marine isotope stage (MIS) 11 dominated by the temperate planktic foraminifer Turborotalita egelida, the MBE experienced a shift to polar assemblages characteristic of predominantly perennial Arctic sea-ice cover during the interglacial and interstadial periods of the last 300 ka. These include the planktic foraminifera Neogloboquadrina pachyderma, the sea-ice dwelling ostracodeAcetabulastoma arcticum and associated benthic taxa Pseudocythere caudata,Pedicythere neofluitans, and Polycope spp. Several species can be used as biostratigraphic markers of specific intervals such as ostracodes Rabilimis mirabilis — MIS 5 and P. vannieuwenhuisei extinction after MIS 11, and foraminiferal abundance zones Bulimina aculeata — late MIS 5 and Bolivina arctica — MIS 5-11.

Anomalous circulation in the Pacific sector of the Arctic Ocean in July-December 2008

NASA Astrophysics Data System (ADS)

Panteleev, G.; Francis, O. P.; Yaremchuk, M.; Zhang, J.; Kulakov, M.; Onat, Y.

2017-12-01

Variability of the mean summer-fall ocean state in the Pacific Sector of the Arctic Ocean (PSAO) is studied using a dynamically constrained synthesis (4Dvar) of historical in situ observations collected during 1972 to 2008. Specifically, the oceanic response to the cyclonic (1989-1996) and anticyclonic (1972-1978, 1997-2006) phases o f the Arctic Ocean Oscillation (AOO) is assessed for the purpose of quantitatively comparing the 2008 circulation pattern that followed the 2007 ice cover minimum.It is shown that the PSAO circulation during July-December of 2008 was characterized by a pronounced negative Sea Surface Height (SSH) anomaly along theEurasian shelf break, which caused a significant decline of the transport in the Atlantic Water (AW) inflow region into the PSAO and increased the sea level difference betweenthe Bering and Chukchi Seas. This anomaly could be one of the reasons for the observed amplification of the Bering Strait transport carrying fresh Pacific Waters into the PSAO. Largrangian analysis of the optimized solution suggests that the freshwater (FW) accumulation in the Beaufort Gyre has a negligible contribution from the East Siberian Sea and is likely caused by the enhanced FW export from the region north of the Canadian Archipelago/Greenland.The inverse modeling results are confirmed by validation against independent altimetry observations and in situ velocity data from NABOS moorings. It is also shown that presented results are in significantly better agreement with the data than the output of the PIOMAS model run utilized as a first guess solution for the 4dVar analysis.

Evolution of the Arctic-North Atlantic and the Western Tethys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ziegler, P.A.

1988-01-01

This volume provides an overview of the late Paleozoic to recent geological evolution of the continents and shelves bordering the North Atlantic Ocean, the Norwegian-Greenland Sea, the Arctic Ocean, and the Mediterranean Sea. The evolution of these seas has been the subject of many studies and compilations, which discuss the evolution of oceanic basins on the basis of their magnetic sea-floor anomalies. The volume presented combines this information with geological data from the adjacent shelf and onshore areas. It retraces the evolution of sedimentary basins developed during the rifting phases that preceded the opening of these oceans and highlights themore » scope of the associated intra-plate phenomena. The author presents a reconstruction of the late Paleozoic and early Mesozoic development of Europe, northernmost Africa and northeastern North America-Greenland and discusses the different orogenic cycles that accompanied the stepwise assembly of Pangea and the early rifting phases heralding its break-up.« less

Aerosol composition and sources in the central Arctic Ocean during ASCOS

NASA Astrophysics Data System (ADS)

Chang, R. Y.-W.; Leck, C.; Graus, M.; Müller, M.; Paatero, J.; Burkhart, J. F.; Stohl, A.; Orr, L. H.; Hayden, K.; Li, S.-M.; Hansel, A.; Tjernström, M.; Leaitch, W. R.; Abbatt, J. P. D.

2011-10-01

Measurements of submicron aerosol chemical composition were made over the central Arctic Ocean from 5 August to 8 September 2008 as a part of the Arctic Summer Cloud Ocean Study (ASCOS) using an aerosol mass spectrometer (AMS). The median levels of sulphate and organics for the entire study were 0.051 and 0.055 μ g m-3, respectively. Positive matrix factorisation was performed on the entire mass spectral time series and this enabled marine biogenic and continental sources of particles to be separated. These factors accounted for 33% and 36% of the sampled ambient aerosol mass, respectively, and they were both predominantly composed of sulphate, with 47% of the sulphate apportioned to marine biogenic sources and 48% to continental sources, by mass. Within the marine biogenic factor, the ratio of methane sulphonate to sulphate was 0.25 ± 0.02, consistent with values reported in the literature. The organic component of the continental factor was more oxidised than that of the marine biogenic factor, suggesting that it had a longer photochemical lifetime than the organics in the marine biogenic factor. The remaining ambient aerosol mass was apportioned to an organic-rich factor that could have arisen from a combination of marine and continental sources. In particular, given that the factor does not correlate with common tracers of continental influence, we cannot rule out that the organic factor arises from a primary marine source.

Proving and Improving Wave Models in the Arctic Ocean and its MIZ

DTIC Science & Technology

2015-09-30

in the central Arctic Ocean (Hunkins, 1966); in the Antarctic MIZ, Weddell Sea, slightly larger values were reported ranging from 1.6 × 10-2 m2 s-1...unprecedented spatial resolution. Such vast fields of pancake ice have traditionally only been associated with the advancing Antarctic MIZ, and, on a smaller...achieved in an MIZ dominated by large waves. Data on the break-up of a large tabular iceberg by swell, measured in Baffin Bay, were published

Petroleum prospectivity of the Canada Basin, Arctic Ocean

USGS Publications Warehouse

Grantz, A.; Hart, P.E.

2011-01-01

Reconnaissance seismic reflection data indicate that Canada Basin is a remnant of the Amerasia Basin of the Arctic Ocean that lies south of the Alpha-Mendeleev Large Igneous Province, which was constructed on the northern part of the Amerasia Basin between about 127 and 89-75 Ma. Canada Basin is filled with Early Jurassic to Holocene detritus from the Mackenzie River system, which drains the northern third of interior North America, with sizable contributions from Alaska and Northwest Canada. Except for the absence of a salt- and shale-bearing mobile substrate Canada Basin is analogous to the Mississippi Delta and the western Gulf of Mexico. Canada Basin contains about 7 to >14 km of sediment beneath the Mackenzie Prodelta on the southeast, 6 to 7 km of sediment beneath the abyssal plain on the west, and roughly 5 or 6 million cubic km of sediment. About three fourths of the basin fill generates low amplitude seismic reflections, interpreted to represent hemiplegic deposits, and a fourth of the fill generates interbedded lenses to extensive layers of moderate to high amplitude reflections interpreted to represent unconfined turbidite and amalgamated channel deposits. Extrapolation from Arctic Alaska and Northwest Canada suggests that three fourths of the section in Canada Basin may contain intervals of hydrocarbon source rocks and the apparent age of the basin suggests that it contains three of the six stratigraphic intervals that together provided >90?? of the World's discovered reserves of oil and gas.. Worldwide heat flow averages suggest that about two thirds of Canada Basin lies in the oil or gas window. At least five types of structural or stratigraphic features of local to regional occurrence offer exploration targets in Canada Basin. These consist of 1) a belt of late Eocene to Miocene shale-cored detachment folds containing with at least two anticlines that are capped by beds with bright spots, 2) numerous moderate to high amplitude reflection packets

The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the Thermohaline Circulation

PubMed Central

Cózar, Andrés; Martí, Elisa; Duarte, Carlos M.; García-de-Lomas, Juan; van Sebille, Erik; Ballatore, Thomas J.; Eguíluz, Victor M.; González-Gordillo, J. Ignacio; Pedrotti, Maria L.; Echevarría, Fidel; Troublè, Romain; Irigoien, Xabier

2017-01-01

The subtropical ocean gyres are recognized as great marine accummulation zones of floating plastic debris; however, the possibility of plastic accumulation at polar latitudes has been overlooked because of the lack of nearby pollution sources. In the present study, the Arctic Ocean was extensively sampled for floating plastic debris from the Tara Oceans circumpolar expedition. Although plastic debris was scarce or absent in most of the Arctic waters, it reached high concentrations (hundreds of thousands of pieces per square kilometer) in the northernmost and easternmost areas of the Greenland and Barents seas. The fragmentation and typology of the plastic suggested an abundant presence of aged debris that originated from distant sources. This hypothesis was corroborated by the relatively high ratios of marine surface plastic to local pollution sources. Surface circulation models and field data showed that the poleward branch of the Thermohaline Circulation transfers floating debris from the North Atlantic to the Greenland and Barents seas, which would be a dead end for this plastic conveyor belt. Given the limited surface transport of the plastic that accumulated here and the mechanisms acting for the downward transport, the seafloor beneath this Arctic sector is hypothesized as an important sink of plastic debris. PMID:28439534

The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the Thermohaline Circulation.

PubMed

Cózar, Andrés; Martí, Elisa; Duarte, Carlos M; García-de-Lomas, Juan; van Sebille, Erik; Ballatore, Thomas J; Eguíluz, Victor M; González-Gordillo, J Ignacio; Pedrotti, Maria L; Echevarría, Fidel; Troublè, Romain; Irigoien, Xabier

2017-04-01

The subtropical ocean gyres are recognized as great marine accummulation zones of floating plastic debris; however, the possibility of plastic accumulation at polar latitudes has been overlooked because of the lack of nearby pollution sources. In the present study, the Arctic Ocean was extensively sampled for floating plastic debris from the Tara Oceans circumpolar expedition. Although plastic debris was scarce or absent in most of the Arctic waters, it reached high concentrations (hundreds of thousands of pieces per square kilometer) in the northernmost and easternmost areas of the Greenland and Barents seas. The fragmentation and typology of the plastic suggested an abundant presence of aged debris that originated from distant sources. This hypothesis was corroborated by the relatively high ratios of marine surface plastic to local pollution sources. Surface circulation models and field data showed that the poleward branch of the Thermohaline Circulation transfers floating debris from the North Atlantic to the Greenland and Barents seas, which would be a dead end for this plastic conveyor belt. Given the limited surface transport of the plastic that accumulated here and the mechanisms acting for the downward transport, the seafloor beneath this Arctic sector is hypothesized as an important sink of plastic debris.

Digital depth horizon compilations of the Alaskan North Slope and adjacent Arctic regions

USGS Publications Warehouse

Saltus, Richard W.; Bird, Kenneth J.

2003-01-01

Data have been digitized and combined to create four detailed depth horizon grids spanning the Alaskan North Slope and adjacent offshore areas. These map horizon compilations were created to aid in petroleum system modeling and related studies. Topography/bathymetry is extracted from a recent Arctic compilation of global onshore DEM and satellite altimetry and ship soundings offshore. The Lower Cretaceous Unconformity (LCU), the top of the Triassic Shublik Formation, and the pre-Carboniferous acoustic basement horizon grids are created from numerous seismic studies, drill hole information, and interpolation. These horizons were selected because they mark critical times in the geologic evolution of the region as it relates to petroleum. The various horizons clearly show the major tectonic elements of this region including the Brooks Range, Colville Trough, Barrow Arch, Hanna Trough, Chukchi Platform, Nuwuk Basin, Kaktovik Basin, and Canada Basin. The gridded data are available in a variety of data formats for use in regional studies.

The melting sea ice of Arctic polar cap in the summer solstice month and the role of ocean

NASA Astrophysics Data System (ADS)

Lee, S.; Yi, Y.

2014-12-01

The Arctic sea ice is becoming smaller and thinner than climatological standard normal and more fragmented in the early summer. We investigated the widely changing Arctic sea ice using the daily sea ice concentration data. Sea ice data is generated from brightness temperature data derived from the sensors: Defense Meteorological Satellite Program (DMSP)-F13 Special Sensor Microwave/Imagers (SSM/Is), the DMSP-F17 Special Sensor Microwave Imager/Sounder (SSMIS) and the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) instrument on the NASA Earth Observing System (EOS) Aqua satellite. We tried to figure out appearance of arctic sea ice melting region of polar cap from the data of passive microwave sensors. It is hard to explain polar sea ice melting only by atmosphere effects like surface air temperature or wind. Thus, our hypothesis explaining this phenomenon is that the heat from deep undersea in Arctic Ocean ridges and the hydrothermal vents might be contributing to the melting of Arctic sea ice.

Freshwater and polynya components of the shelf-derived Arctic Ocean halocline in summer 2007 identified by stable oxygen isotopes

NASA Astrophysics Data System (ADS)

Bauch, D.; Rutgers van der Loeff, M.; Andersen, N.; Torres-Valdes, S.; Bakker, K.; Abrahamsen, E.

2011-12-01

With the aim of determining the origin of freshwater in the halocline, fractions of river water and sea-ice meltwater (or brine influence from sea-ice formation) in the upper 150 m were quantified by a combination of salinity and δ18O and nutrients in the Eurasian basins and the Makarov Basin. Our study indicates which layers of the Arctic Ocean halocline are primarily influenced by sea-ice formation in coastal polynyas and which are primarily influenced by sea-ice formation over the open ocean. With the ongoing changes in sea-ice coverage in the Arctic Ocean it can be expected that these processes will change in the immediate future and that the relative contributions to the halocline will change accordingly. Within the Eurasian Basin a west to east oriented front between net melting and production of sea-ice is observed. Outside the Atlantic regime dominated by net sea-ice melting, a pronounced layer influenced by brines released during sea-ice formation is present at about 30 to 50 m water depth with a maximum over the Lomonosov Ridge. The geographically distinct definition of this maximum demonstrates the rapid release and transport of signals from the shelf regions in discrete pulses within the Transpolar Drift. We use the ratio of sea-ice derived brine influence and river water to link the maximum in brine influence within the Transpolar Drift with a pulse of shelf waters from the Laptev Sea likely released in summer 2005. For a distinction of Atlantic and Pacific-derived contributions the initial phosphate corrected for mineralization with oxygen (PO*) and alternatively the nitrate to phosphate ratio (N/P) in each sample were used. While PO*-based assessments systematically underestimate the contribution of Pacific-derived waters, N/P-based calculations overestimate Pacific-derived waters within the Transpolar Drift due to denitrification in bottom sediments of the Laptev Sea. The extent of Pacific-derived water in the Arctic Ocean was approximately limited

Impact of Northern Hemisphere polar gateways on the Arctic Ocean climate during the latest Cretaceous as simulated by an Earth System Model.

NASA Astrophysics Data System (ADS)

Niezgodzki, Igor; Knorr, Gregor; Lohmann, Gerrit; Tyszka, Jarosław

2017-04-01

Using the Earth System Model COSMOS, we simulate the Late Cretaceous climate with different gateway configurations in the Arctic Ocean region under constant CO2 level of 1120 ppm (4 x pre-industrial). Based on the Maastrichtian paleogeography, we modify gateway configurations in the Arctic region according to different scenarios recorded from the Campanian - Maastrichtian ( 83-66 Ma). Our simulation with the Greenland-Norwegian Sea even as deep as 1.5 km in the Campanian produces consistent salinities in the Greenland-Norwegian Sea and in the surface Arctic Ocean, with the proxy-based salinity reconstructions. Towards the end of the Maastrichtian the gateway became shallower but didn't close entirely before the K-Pg boundary. During entire interval, the simulated salinity in the Arctic Ocean was well stratified, in agreement with the data. The surface ocean became progressively fresher, starting from the moderately brackish conditions in the Campanian to the (almost) freshwater conditions around the K-Pg boundary. Arctic gateways configuration changes cannot reproduce cooling trends as reconstructed by the proxy data during the Campanian - Maastrichtian interval. Our additional sensitivity tests with the different CO2 levels (1-6 x pre-industrial) and fixed (Maastrichtian) paleogeography show that a doubling of atmospheric CO2 concentration from 560 ppm to 1120 ppm results in an increase in the zonal mean surface air temperature in the polar regions by as high as 10°C. This suggests that the CO2 level decline, rather than gateway configuration changes, was responsible for the cooling trend toward the end of the Maastrichtian. The research was supported from the grant of the National Science Center in Poland based on the decision DEC-2012/07/N/ST10/03419.

Source- and degradation-diagnostic of colloidal organic matter exported by rivers across the Eurasian Arctic margin

NASA Astrophysics Data System (ADS)

Karlsson, Emma; Gelting, Johan; Tesi, Tommaso; van Dongen, Bart; Kruså, Martin; Vonk, Jorien; Sanchez-Garcia, Laura; Semiletov, Igor; Charkin, Alexander; Dudarev, Oleg; Gustafsson, Örjan

2013-04-01

Both models and in-situ observations indicate that the Arctic watersheds will experience a significant increase in temperature, resulting in higher runoff and remobilization of the vast carbon reservoirs currently held stable under frozen conditions. However, the sources and degradability of the dissolved organic carbon (DOC) released to this aquatic land-ocean conduit in high latitude regions is still poorly constrained. For example, there is a particular lack in our understanding of the fate of the DOC once it enters the Arctic Ocean. This study therefore investigated the compositional changes of the organic colloidal material along the Arctic land-ocean continuum. Large-volume samples of high-molecular weight DOC (colloids) were isolated as part of the International Siberian Shelf Study 2008 (ISSS-08) using 1000 D cross-flow ultrafiltration outside the mouths of Arctic rivers Ob, Yenisey, Lena, Indigirka and Kolyma as well as on the adjacent continental shelf seas Laptev Sea and the East Siberian Sea. The colloidal fraction was characterized by both bulk isotope parameters (δ13C and Δ14C) and with macromolecular biomarkers such as free lipids (n-alkanes, n-alkanoic acids, n-alkanols) and CuO reaction products (lignin phenols, cutin derived-products, protein and lipid products). In this presentation we will focus on regional differences between contrasting watersheds characterized by different climate and vegetation as well as permafrost conditions. Particular emphasis will be placed on origin, degradation, and dilution of the terrigenous colloidal material during its transport from land to the ocean. Finally, the comparison between the dissolved and particulate fractions will also be presented to highlight differences and similarities between these two pools of aquatic carbon.

The large-scale freshwater cycle of the Arctic

NASA Astrophysics Data System (ADS)

Serreze, Mark C.; Barrett, Andrew P.; Slater, Andrew G.; Woodgate, Rebecca A.; Aagaard, Knut; Lammers, Richard B.; Steele, Michael; Moritz, Richard; Meredith, Michael; Lee, Craig M.

2006-11-01

This paper synthesizes our understanding of the Arctic's large-scale freshwater cycle. It combines terrestrial and oceanic observations with insights gained from the ERA-40 reanalysis and land surface and ice-ocean models. Annual mean freshwater input to the Arctic Ocean is dominated by river discharge (38%), inflow through Bering Strait (30%), and net precipitation (24%). Total freshwater export from the Arctic Ocean to the North Atlantic is dominated by transports through the Canadian Arctic Archipelago (35%) and via Fram Strait as liquid (26%) and sea ice (25%). All terms are computed relative to a reference salinity of 34.8. Compared to earlier estimates, our budget features larger import of freshwater through Bering Strait and larger liquid phase export through Fram Strait. While there is no reason to expect a steady state, error analysis indicates that the difference between annual mean oceanic inflows and outflows (˜8% of the total inflow) is indistinguishable from zero. Freshwater in the Arctic Ocean has a mean residence time of about a decade. This is understood in that annual freshwater input, while large (˜8500 km3), is an order of magnitude smaller than oceanic freshwater storage of ˜84,000 km3. Freshwater in the atmosphere, as water vapor, has a residence time of about a week. Seasonality in Arctic Ocean freshwater storage is nevertheless highly uncertain, reflecting both sparse hydrographic data and insufficient information on sea ice volume. Uncertainties mask seasonal storage changes forced by freshwater fluxes. Of flux terms with sufficient data for analysis, Fram Strait ice outflow shows the largest interannual variability.

Alkenone-based reconstructions show four-phase Holocene temperature history for Arctic Svalbard

NASA Astrophysics Data System (ADS)

van der Bilt, W. G. M.; D'Andrea, W. J.; Bakke, J.; Balascio, N.; Werner, J.; Bradley, R. S.

2016-12-01

Situated at the crossroads of global oceanic and atmospheric circulation patterns, the Arctic is a key component of Earth`s climate system. Amplified by sea-ice feedbacks, even modest shifts in regional heat budget drive large climate responses. This is highlighted by the dramatic response of the Arctic to global warming. Assessing the signature of underlying forcings require paleoclimate records, allowing us to expand our knowledge beyond the short instrumental period and contextualize ongoing warming. However, such data are scarce and sparse in the Arctic, limiting our ability to address these issues. We present two quantitative Holocene-length summer temperature reconstructions from the Arctic Svalbard archipelago. Temperature estimates are based on alkenone unsaturation ratios measured on sediment cores from two lakes. Our data reveal a dynamic Holocene temperature history, with reconstructed lake water temperatures spanning a range of 6-8 °C, and characterized by four phases. The Early Holocene was marked by an early ( 10.5 ka cal. BP) onset of insolation-driven Hypsithermal conditions, likely compounded by strengthening oceanic heat transport. This warm interval was interrupted by cooling between 10.5-8.3 ka cal. BP that we attribute to cooling effects from the melting Northern Hemisphere ice sheets. Temperatures declined throughout the Middle Holocene, following a gradual trend that was accentuated by two cooling steps between 7.8-7 ka cal. BP and 4.4-3.5 ka cal. BP. These transitions coincide with a strengthening influence of Arctic water and sea-ice in the adjacent eastern Fram Strait. During the Late Holocene (past 4 ka), temperature change decoupled from the still-declining insolation, and fluctuated around cold mean conditions. This study improves our understanding of Arctic climate dynamics by demonstrating that Holocene Svalbard temperatures were governed by an alternation of forcing mechanism.

Paleogene blackshales in the central Arctic Ocean and paleoenvironment: Anoxia vs. high primary production vs. terrigenous input

NASA Astrophysics Data System (ADS)

Stein, R.; Weller, P.; Boucsein, B.

2006-12-01

During IODP Expedition 302 (Arctic Ocean Coring Experiment ACEX), the first scientific drilling campaign in the permantly ice-covered central Arctic Ocean on Lomonosov Ridge, a 430 m thick sequence of upper Cretaceaous to Quaternary sediments has been drilled. Here we present detailed organic carbon (OC) records from the entire ca. 200 m thick, upper Paleocene to middle Eocene blackshale-type section of the ACEX drill sites, characterized by OC contents of about 1 to 6%. Based on a multi-proxy organic geochemical approach (hydrogen indices, C/N and C/S ratios, stable carbon isotopes, biomarkers, and maceral composition), organic-carbon sources and paleoenvironmental conditions were reconstructed. The late Paleocene interval is characterized by oxic conditions and a predominance of reworked terrigenous OC. In contrast, euxinic "Black Sea-type" conditions favorable for the preservation of labile aquatic (marine algae-type) OC occur throughout the upper part of the early Eocene and the middle Eocene, explained by salinity stratification due to freshwater discharge. The superimposed short-term ("Milankovitch-type") variability in amount and composition of OC is related to changes in primary production and terrigenous input. Prominent early Eocene events of algae-type OC preservation coincide with global 13C events such as the Paleocene- Eocece Thermal Maximum (PETM) and Elmo events. During Eocene times of anoxia, OC accumulation rates were 5-20 times higher than modern ones. Whereas very low organic carbon accumulation rates of about 0.005 gC cm-2 ky-1 are typical for the modern (Holocene) central Arctic Ocean on Lomonosov Ridge, values of up to 0.1-0.15 gC cm-2 ky-1 were calculated for the Eocene ACEX section. Because major part of the OC deposited during Eocene times is of aquatic (marine) origin and the OC deposited during Holocene times is almost entirely of terrigenous origin, the difference between the modern and Eocene situation becomes even more drastic when

Empirical ocean color algorithms and bio-optical properties of the western coastal waters of Svalbard, Arctic

NASA Astrophysics Data System (ADS)

Son, Young-Sun; Kim, Hyun-cheol

2018-05-01

Chlorophyll (Chl) concentration is one of the key indicators identifying changes in the Arctic marine ecosystem. However, current Chl algorithms are not accurate in the Arctic Ocean due to different bio-optical properties from those in the lower latitude oceans. In this study, we evaluated the current Chl algorithms and analyzed the cause of the error in the western coastal waters of Svalbard, which are known to be sensitive to climate change. The NASA standard algorithms showed to overestimate the Chl concentration in the region. This was due to the high non-algal particles (NAP) absorption and colored dissolved organic matter (CDOM) variability at the blue wavelength. In addition, at lower Chl concentrations (0.1-0.3 mg m-3), chlorophyll-specific absorption coefficients were ∼2.3 times higher than those of other Arctic oceans. This was another reason for the overestimation of Chl concentration. OC4 algorithm-based regionally tuned-Svalbard Chl (SC4) algorithm for retrieving more accurate Chl estimates reduced the mean absolute percentage difference (APD) error from 215% to 49%, the mean relative percentage difference (RPD) error from 212% to 16%, and the normalized root mean square (RMS) error from 211% to 68%. This region has abundant suspended matter due to the melting of tidal glaciers. We evaluated the performance of total suspended matter (TSM) algorithms. Previous published TSM algorithms generally overestimated the TSM concentration in this region. The Svalbard TSM-single band algorithm for low TSM range (ST-SB-L) decreased the APD and RPD errors by 52% and 14%, respectively, but the RMS error still remained high (105%).

Pelagic Nitrogen Cycle Observations In The Arctic Ocean - How Might They Change In Response To Ocean Acidification?

NASA Astrophysics Data System (ADS)

Clark, D. R.; Rees, A.; Brown, I.; Al-Moosawi, L.; Cripps, G.

2016-02-01

Phytoplankton forms the base of marine food webs by assimilating nutrients and generating biomass that supports higher trophic levels. Conversely, marine heterotrophs degrade organic matter produced by phytoplankton and recycle nutrients, maintaining food web integrity. We investigated the assimilation and regeneration of dissolved inorganic nitrogen (DIN) at stations located in the Arctic Ocean. In addition, we measured the concentration of nitrous oxide, a by-product of N-regeneration (specifically nitrification) and a climatically active gas. Measurements demonstrated the simultaneous regeneration and assimilation of ammonium, nitrite and nitrate at open ocean, ice-edge and within-ice locations. Ammonium was regenerated and assimilated within the range 0.2-4.5 nmol·L-1·h-1 and 0.5-24.8 nmol·L-1·h-1 respectively. Nitrite was regenerated and assimilated within the range 0.1-9.2 nmol·L-1·h-1 and 0.0-6.9 nmol·L-1·h-1 respectively. Nitrate was regenerated and assimilated within the range 0.3-372.7 nmol·L-1·h-1 and 0.1-48.3 nmol·L-1·h-1 respectively. Results indicated that the ice-edge was associated with enhanced DIN assimilation. The concentration of nitrous oxide (<100m) averaged 11.8±2.2 nmol·L-1, which was approximately 15% higher than measured in the European shelf seas and most likely related only to temperature. In separate experiments, the influence of ocean acidification (OA) upon nitrogen cycle processes was investigated. The carbonate system of photic zone seawater (depth <10m) was modified to achieve a range of PCO2 concentrations using bioassay experiments. Preliminary results indicated that NH4+ oxidation and the concentration of nitrous oxide did not respond in a clear or consistent way to OA treatments. In contrast, the regeneration of NH4+ increased in response to elevated PCO2. The bacterial degradation of organic matter may be enhanced in the Arctic Ocean in response to OA, potentially modifying DIN pool composition and concentration

Contemporary Arctic Sea Level

NASA Astrophysics Data System (ADS)

Cazenave, A. A.

2017-12-01

During recent decades, the Arctic region has warmed at a rate about twice the rest of the globe. Sea ice melting is increasing and the Greenland ice sheet is losing mass at an accelerated rate. Arctic warming, decrease in the sea ice cover and fresh water input to the Arctic ocean may eventually impact the Arctic sea level. In this presentation, we review our current knowledge of contemporary Arctic sea level changes. Until the beginning of the 1990s, Arctic sea level variations were essentially deduced from tide gauges located along the Russian and Norwegian coastlines. Since then, high inclination satellite altimetry missions have allowed measuring sea level over a large portion of the Arctic Ocean (up to 80 degree north). Measuring sea level in the Arctic by satellite altimetry is challenging because the presence of sea ice cover limits the full capacity of this technique. However adapted processing of raw altimetric measurements significantly increases the number of valid data, hence the data coverage, from which regional sea level variations can be extracted. Over the altimetry era, positive trend patterns are observed over the Beaufort Gyre and along the east coast of Greenland, while negative trends are reported along the Siberian shelf. On average over the Arctic region covered by satellite altimetry, the rate of sea level rise since 1992 is slightly less than the global mea sea level rate (of about 3 mm per year). On the other hand, the interannual variability is quite significant. Space gravimetry data from the GRACE mission and ocean reanalyses provide information on the mass and steric contributions to sea level, hence on the sea level budget. Budget studies show that regional sea level trends over the Beaufort Gyre and along the eastern coast of Greenland, are essentially due to salinity changes. However, in terms of regional average, the net steric component contributes little to the observed sea level trend. The sea level budget in the Arctic

Meltwater and precipitation runoff to the North Atlantic, Arctic, and Gulf of Mexico from the Laurentide Ice Sheet and adjacent regions during the Younger Dryas

NASA Astrophysics Data System (ADS)

Teller, James T.

1990-12-01

Runoff from North America may have played a significant role in ocean circulation and climate change during the last deglaciation. Because the driving force behind such changes may have been related to salinity of the north flowing Atlantic Ocean conveyor circulation, it is critical to know the volume, timing, and location of fresh water entering the North Atlantic from the melting Laurentide Ice Sheet. During the Younger Dryas cold episode, 11,000-10,000 years B.P., there was a two-fold increase in the volume of meltwater plus precipitation runoff, to more than 1700 km³ yr-1, flowing through the St. Lawrence valley to the North Atlantic, mainly because retreating ice allowed the glacial Lake Agassiz basin to drain eastward into the Great Lakes at this time. There was a corresponding decline in discharge from Lake Agassiz through the Mississippi River to the Gulf of Mexico. Runoff to the Arctic Ocean also increased at about the beginning of the Younger Dryas, from 740 to 900 km³ yr-1, because of the capture of what is now the headwater region of the Mackenzie River watershed. This, in combination with rising sea level and warming climate, may have increased the amount of pack ice reaching the North Atlantic through the Norwegian Sea from the Arctic Ocean. At 10,000 years B.P., eastward overflow from the western interior of North America was blocked by advancing ice, again forcing overflow to the Gulf of Mexico and, possibly, to the northwest into the Arctic Ocean. Although total runoff to the oceans from all regions draining from the Laurentide Ice Sheet did not vary substantially between 12,000 and 9000 years B.P., if discharge to the Gulf of Mexico is excluded, fresh water reaching the North Atlantic averaged 4000 km³ yr-1 during the Younger Dryas, in contrast to 2870 km³ yr-1 just before this cold episode and 3440 km³ yr-1 just after it.

Role of Greenland meltwater in the changing Arctic

NASA Astrophysics Data System (ADS)

Dukhovskoy, Dmitry; Proshutinsky, Andrey; Timmermans, Mary-Louise; Myers, Paul; Platov, Gennady; Bamber, Jonathan; Curry, Beth; Somavilla, Raquel

2016-04-01

Observational data show that the Arctic ocean-ice-atmosphere system has been changing over the last two decades. Arctic change is manifest in the atypical behavior of the climate indices in the 21st century. Before the 2000s, these indices characterized the quasi-decadal variability of the Arctic climate related to different circulation regimes. Between 1948 and 1996, the Arctic atmospheric circulation alternated between anticyclonic circulation regimes and cyclonic circulation regimes with a period of 10-15 years. Since 1997, however, the Arctic has been dominated by an anticyclonic regime. Previous studies indicate that in the 20th century, freshwater and heat exchange between the Arctic Ocean and the sub-Arctic seas were self-regulated and their interactions were realized via quasi-decadal climate oscillations. What physical processes in the Arctic Ocean - sub-Arctic ocean-ice-atmosphere system are responsible for the observed changes in Arctic climate variability? The presented work is motivated by our hypothesis that in the 21st century, these quasi-decadal oscillations have been interrupted as a result of an additional freshwater source associated with Greenland Ice Sheet melt. Accelerating since the early 1990s, the Greenland Ice Sheet mass loss exerts a significant impact on thermohaline processes in the sub-Arctic seas. Surplus Greenland freshwater, the amount of which is about a third of the freshwater volume fluxed into the region during the 1970s Great Salinity Anomaly event, can spread and accumulate in the sub-Arctic seas influencing convective processes there. It is not clear, however, whether Greenland freshwater can propagate into the interior convective regions in the Labrador Sea and the Nordic Seas. In order to investigate the fate and pathways of Greenland freshwater in the sub-Arctic seas and to determine how and at what rate Greenland freshwater propagates into the convective regions, several numerical experiments using a passive tracer to

An Intensified Arctic Water Cycle? Trend Analysis of the Arctic System Freshwater Cycle: Observations and Expectations

NASA Astrophysics Data System (ADS)

Rawlins, M. A.; Adam, J. C.; Vorosmarty, C. J.; Serreze, M. C.; Hinzman, L. D.; Holland, M.; Shiklomanov, A.

2007-12-01

It is expected that a warming climate will be attended by an intensification of the global hydrological cycle. While there are signs of positive trends in several hydrological quantities emerging at the global scale, the scope, character, and quantitative significance of these changes are not well established. In particular, long-term increases in river discharge across Arctic Eurasia are assumed to represent such an intensification and have received considerable attention. Yet, no change in long-term annual precipitation across the region can be related with the discharge trend. Given linkages and feedbacks between the arctic and global climate systems, a more complete understanding of observed changes across northern high latitudes is needed. We present a working definition of an accelerated or intensified hydrological cycle and a synthesis of long-term (nominally 50 years) trends in observed freshwater stocks and fluxes across the arctic land-atmosphere-ocean system. Trend and significance measures from observed data are described alongside expectations of intensification based on GCM simulations of contemporary and future climate. Our domain of interest includes the terrestrial arctic drainage (including all of Alaska and drainage to Hudson Bay), the Arctic Ocean, and the atmosphere over the land and ocean domains. For the terrestrial Arctic, time series of spatial averages which are derived from station data and atmospheric reanalysis are available. Reconstructed data sets are used for quantities such as Arctic Ocean ice and liquid freshwater transports. Study goals include a comprehensive survey of past changes in freshwater across the pan-arctic and a set of benchmarks for expected changes based on an ensemble of GCM simulations, and identification of potential mechanistic linkages which may be examined with contemporary remote sensing data sets.

No maternal or direct effects of ocean acidification on egg hatching in the Arctic copepod Calanus glacialis.

PubMed

Thor, Peter; Vermandele, Fanny; Carignan, Marie-Helene; Jacque, Sarah; Calosi, Piero

2018-01-01

Widespread ocean acidification (OA) is transforming the chemistry of the global ocean and the Arctic is recognised as the region where this transformation will occur at the fastest rate. Moreover, many Arctic species are considered less capable of tolerating OA due to their lower capacity for acid-base regulation. This inability may put severe restraints on many fundamental functions, such as growth and reproductive investments, which ultimately may result in reduced fitness. However, maternal effects may alleviate severe effects on the offspring rendering them more tolerant to OA. In a highly replicated experiment we studied maternal and direct effects of OA predicted for the Arctic shelf seas on egg hatching time and success in the keystone copepod species Calanus glacialis. We incubated females at present day conditions (pHT 8.0) and year 2100 extreme conditions (pHT 7.5) during oogenesis and subsequently reciprocally transplanted laid eggs between these two conditions. Statistical tests showed no effects of maternal or direct exposure to OA at this level. We hypothesise that C. glacialis may be physiologically adapted to egg production at low pH since oogenesis can also take place at conditions of potentially low haemolymph pH of the mother during hibernation in the deep.

Variability of the Arctic Basin Oceanographic Fields

DTIC Science & Technology

1996-02-01

the model a very sophisticated turbulence closure scheme. 9. Imitation of the CO2 doubling We parameterized the " greenhouse " effect by changing the...of the Arctic Ocean. A more realistic model of the Arctic Ocean circulation was obtained, and an estimation of the impact of the greenhouse effect on... greenhouse effect is in freshening of the upper Arctic Basin. Although some shortcomings of the model still exist (an unrealistic high coefficient of

Implications of sea-ice biogeochemistry for oceanic production and emissions of dimethyl sulfide in the Arctic

NASA Astrophysics Data System (ADS)

Hayashida, Hakase; Steiner, Nadja; Monahan, Adam; Galindo, Virginie; Lizotte, Martine; Levasseur, Maurice

2017-06-01

Sea ice represents an additional oceanic source of the climatically active gas dimethyl sulfide (DMS) for the Arctic atmosphere. To what extent this source contributes to the dynamics of summertime Arctic clouds is, however, not known due to scarcity of field measurements. In this study, we developed a coupled sea ice-ocean ecosystem-sulfur cycle model to investigate the potential impact of bottom-ice DMS and its precursor dimethylsulfoniopropionate (DMSP) on the oceanic production and emissions of DMS in the Arctic. The results of the 1-D model simulation were compared with field data collected during May and June of 2010 in Resolute Passage. Our results reproduced the accumulation of DMS and DMSP in the bottom ice during the development of an ice algal bloom. The release of these sulfur species took place predominantly during the earlier phase of the melt period, resulting in an increase of DMS and DMSP in the underlying water column prior to the onset of an under-ice phytoplankton bloom. Production and removal rates of processes considered in the model are analyzed to identify the processes dominating the budgets of DMS and DMSP both in the bottom ice and the underlying water column. When openings in the ice were taken into account, the simulated sea-air DMS flux during the melt period was dominated by episodic spikes of up to 8.1 µmol m-2 d-1. Further model simulations were conducted to assess the effects of the incorporation of sea-ice biogeochemistry on DMS production and emissions, as well as the sensitivity of our results to changes of uncertain model parameters of the sea-ice sulfur cycle. The results highlight the importance of taking into account both the sea-ice sulfur cycle and ecosystem in the flux estimates of oceanic DMS near the ice margins and identify key uncertainties in processes and rates that should be better constrained by new observations.

Arctic Climate and Atmospheric Planetary Waves

NASA Technical Reports Server (NTRS)

Cavalieri, D. J.; Haekkinen, S.

2000-01-01

Analysis of a fifty-year record (1946-1995) of monthly-averaged sea level pressure data provides a link between the phases of planetary-scale sea level pressure waves and Arctic Ocean and ice variability. Results of this analysis show: (1) a breakdown of the dominant wave I pattern in the late 1960's, (2) shifts in the mean phase of waves 1 and 2 since this breakdown, (3) an eastward shift in the phases of both waves 1 and 2 during the years of simulated cyclonic Arctic Ocean circulation relative to their phases during the years of anticyclonic circulation, (4) a strong decadal variability of wave phase associated with simulated Arctic Ocean circulation changes. Finally, the Arctic atmospheric circulation patterns that emerge when waves 1 and 2 are in their extreme eastern and western positions suggest an alternative approach to determine significant forcing patterns of sea ice and high-latitude variability.

Jellies under ice: ROV observations from the Arctic 2005 hidden ocean expedition

NASA Astrophysics Data System (ADS)

Raskoff, K. A.; Hopcroft, R. R.; Kosobokova, K. N.; Purcell, J. E.; Youngbluth, M.

2010-01-01

In order to provide a baseline understanding of gelatinous zooplankton biodiversity and distribution in the rapidly changing Arctic Ocean, 12 stations were sampled across the Canada Basin, Northwind Ridge, and Chukchi Plateau with detailed deep-water ROV observations and multinet tows down to 3000 m. The complex, multi-origin water layers of the Arctic Ocean provided the backdrop for examining the vertical and horizontal distributions of the poorly understood meso and bathypelagic gelatinous taxa. Over 50 different gelatinous taxa were observed across the stations, with cnidarians being the most common group. Medusae accounted for 60% of all observations, siphonophores for 24%, larvaceans for 10%, ctenophores for 5%, and numerous interesting and rarer taxa constituted the remaining 1% of observations. Several new species were found and many major range extensions were observed. Both the vertical and horizontal distribution of species appear to be linked to water mass characteristics, as well as bottom topography and geographic location within the study area. Shallow slope and ridge areas around the Canada Basin and Chukchi Plateau appear to harbor substantially lower gelatinous zooplankton biomass and diversity than the deeper locations. Shallow stations not only show reduced abundance, but also different relative abundance of the major taxa, where the shallow water stations are dominated by large numbers of siphonophores and ctenophores, the deep stations are dominated by medusae. Taxonomic issues and ecological observations of several important species are discussed, aided by the live collection of many undamaged and fragile species.

Development of pan-Arctic database for river chemistry

USGS Publications Warehouse

McClelland, J.W.; Holmes, R.M.; Peterson, B.J.; Amon, R.; Brabets, T.; Cooper, L.; Gibson, J.; Gordeev, V.V.; Guay, C.; Milburn, D.; Staples, R.; Raymond, P.A.; Shiklomanov, I.; Striegl, Robert G.; Zhulidov, A.; Gurtovaya, T.; Zimov, S.

2008-01-01

More than 10% of all continental runoff flows into the Arctic Ocean. This runoff is a dominant feature of the Arctic Ocean with respect to water column structure and circulation. Yet understanding of the chemical characteristics of runoff from the pan-Arctic watershed is surprisingly limited. The Pan- Arctic River Transport of Nutrients, Organic Matter, and Suspended Sediments ( PARTNERS) project was initiated in 2002 to help remedy this deficit, and an extraordinary data set has emerged over the past few years as a result of the effort. This data set is publicly available through the Cooperative Arctic Data and Information Service (CADIS) of the Arctic Observing Network (AON). Details about data access are provided below.

Sensitivity to ocean acidification parallels natural pCO2 gradients experienced by Arctic copepods under winter sea ice

PubMed Central

Lewis, Ceri N.; Brown, Kristina A.; Edwards, Laura A.; Cooper, Glenn; Findlay, Helen S.

2013-01-01

The Arctic Ocean already experiences areas of low pH and high CO2, and it is expected to be most rapidly affected by future ocean acidification (OA). Copepods comprise the dominant Arctic zooplankton; hence, their responses to OA have important implications for Arctic ecosystems, yet there is little data on their current under-ice winter ecology on which to base future monitoring or make predictions about climate-induced change. Here, we report results from Arctic under-ice investigations of copepod natural distributions associated with late-winter carbonate chemistry environmental data and their response to manipulated pCO2 conditions (OA exposures). Our data reveal that species and life stage sensitivities to manipulated OA conditions were correlated with their vertical migration behavior and with their natural exposures to different pCO2 ranges. Vertically migrating adult Calanus spp. crossed a pCO2 range of >140 μatm daily and showed only minor responses to manipulated high CO2. Oithona similis, which remained in the surface waters and experienced a pCO2 range of <75 μatm, showed significantly reduced adult and nauplii survival in high CO2 experiments. These results support the relatively untested hypothesis that the natural range of pCO2 experienced by an organism determines its sensitivity to future OA and highlight that the globally important copepod species, Oithona spp., may be more sensitive to future high pCO2 conditions compared with the more widely studied larger copepods. PMID:24297880

Oil and Gas Development in the Arctic Ocean -- Understanding the Legal and Regulatory Framework

DTIC Science & Technology

2008-09-01

by the U.S. Department of Commerce, National Oceanic Atmospheric Administration, National Marine Fisheries Service (NMFS), and the U.S. Department of...in the Arctic Slope Region.60 To the present day, native communities continue to argue that "their continued social, cultural, and economic well...sound levels from seismic and drilling operations. The hunt for the Bowhead is central to some native cultures.62 Native Alaskan communities have argued

Fast Response of the Tropics to an Abrupt Loss of Arctic Sea Ice via Ocean Dynamics

NASA Astrophysics Data System (ADS)

Wang, Kun; Deser, Clara; Sun, Lantao; Tomas, Robert A.

2018-05-01

The role of ocean dynamics in the transient adjustment of the coupled climate system to an abrupt loss of Arctic sea ice is investigated using experiments with Community Climate System Model version 4 in two configurations: a thermodynamic slab mixed layer ocean and a full-depth ocean that includes both dynamics and thermodynamics. Ocean dynamics produce a distinct sea surface temperature warming maximum in the eastern equatorial Pacific, accompanied by an equatorward intensification of the Intertropical Convergence Zone and Hadley Circulation. These tropical responses are established within 25 years of ice loss and contrast markedly with the quasi-steady antisymmetric coupled response in the slab-ocean configuration. A heat budget analysis reveals the importance of anomalous vertical advection tied to a monotonic temperature increase below 200 m for the equatorial sea surface temperature warming maximum in the fully coupled model. Ocean dynamics also rapidly modify the midlatitude atmospheric response to sea ice loss.

An Assessment of State-of-the-Art Mean Sea Surface and Geoid Models of the Arctic Ocean: Implications for Sea Ice Freeboard Retrieval

NASA Astrophysics Data System (ADS)

Skourup, Henriette; Farrell, Sinéad Louise; Hendricks, Stefan; Ricker, Robert; Armitage, Thomas W. K.; Ridout, Andy; Andersen, Ole Baltazar; Haas, Christian; Baker, Steven

2017-11-01

State-of-the-art Arctic Ocean mean sea surface (MSS) models and global geoid models (GGMs) are used to support sea ice freeboard estimation from satellite altimeters, as well as in oceanographic studies such as mapping sea level anomalies and mean dynamic ocean topography. However, errors in a given model in the high-frequency domain, primarily due to unresolved gravity features, can result in errors in the estimated along-track freeboard. These errors are exacerbated in areas with a sparse lead distribution in consolidated ice pack conditions. Additionally model errors can impact ocean geostrophic currents, derived from satellite altimeter data, while remaining biases in these models may impact longer-term, multisensor oceanographic time series of sea level change in the Arctic. This study focuses on an assessment of five state-of-the-art Arctic MSS models (UCL13/04 and DTU15/13/10) and a commonly used GGM (EGM2008). We describe errors due to unresolved gravity features, intersatellite biases, and remaining satellite orbit errors, and their impact on the derivation of sea ice freeboard. The latest MSS models, incorporating CryoSat-2 sea surface height measurements, show improved definition of gravity features, such as the Gakkel Ridge. The standard deviation between models ranges 0.03-0.25 m. The impact of remaining MSS/GGM errors on freeboard retrieval can reach several decimeters in parts of the Arctic. While the maximum observed freeboard difference found in the central Arctic was 0.59 m (UCL13 MSS minus EGM2008 GGM), the standard deviation in freeboard differences is 0.03-0.06 m.

Long-Term Observations of Atmospheric CO2, O3 and BrO over the Transitioning Arctic Ocean Pack-ice: The O-Buoy Chemical Network

NASA Astrophysics Data System (ADS)

Matrai, P.

2016-02-01

Autonomous, sea ice-tethered O-Buoys have been deployed (2009-2016) across the Arctic sea ice for long-term atmospheric measurements (http://www.o-buoy.org). O-Buoys (15) provide in-situ concentrations of three sentinel atmospheric chemicals, ozone, CO2 and BrO, as well as meteorological parameters and imagery, over the frozen ocean. O-Buoys were designed to transmit daily data over a period of 2 years while deployed in sea ice, as part of automated ice-drifting stations that include snow/ice measurement systems (e.g. Ice Mass Balance buoys) and oceanographic measurements (e.g. Ice Tethered Profilers). Seasonal changes in Arctic atmospheric chemistry are influenced by changes in the characteristics and presence of the sea ice vs. open water as well as air mass trajectories, especially during the winter-spring and summer-fall transitions when sea ice is melting and freezing, respectively. The O-Buoy Chemical Network provides the unique opportunity to observe these transition periods in real-time with high temporal resolution, and to compare them with those collected on land-based monitoring stations located. Due to the logistical challenges of measurements over the Arctic Ocean region, most long term, in-situ observations of atmospheric chemistry have been made at coastal or island sites around the periphery of the Arctic Ocean, leaving large spatial and temporal gaps that O-Buoys overcome. Advances in floatation, communications, power management, and sensor hardware have been made to overcome the challenges of diminished Arctic sea ice. O-Buoy data provide insights into enhanced seasonal, interannual and spatial variability in atmospheric composition, atmospheric boundary layer control on the amount of halogen activation, enhancement of the atmospheric CO2 signal over the more variable and porous pack ice, and to develop an integrated picture of the coupled ocean/ice/atmosphere system. As part of the Arctic Observing Network, we provide data to the community (www.aoncadis.org).

Synthesis of integrated primary production in the Arctic Ocean: II. In situ and remotely sensed estimates

NASA Astrophysics Data System (ADS)

Hill, Victoria J.; Matrai, Patricia A.; Olson, Elise; Suttles, S.; Steele, Mike; Codispoti, L. A.; Zimmerman, Richard C.

2013-03-01

Recent warming of surface waters, accompanied by reduced ice thickness and extent may have significant consequences for climate-driven changes of primary production (PP) in the Arctic Ocean (AO). However, it has been difficult to obtain a robust benchmark estimate of pan-Arctic PP necessary for evaluating change. This paper provides an estimate of pan-Arctic PP prior to significant warming from a synthetic analysis of the ARCSS-PP database of in situ measurements collected from 1954 to 2007 and estimates derived from satellite-based observations from 1998 to 2007. Vertical profiles of in situ chlorophyll a (Chl a) and PP revealed persistent subsurface peaks in biomass and PP throughout the AO during most of the summer period. This was contradictory with the commonly assumed exponential decrease in PP with depth on which prior satellite-derived estimates were based. As remotely sensed Chl a was not a good predictor of integrated water column Chl a, accurate satellite-based modeling of vertically integrated primary production (IPPsat), requires knowledge of the subsurface distribution of phytoplankton, coincident with the remotely sensed ocean color measurements. We developed an alternative approach to modeling PP from satellite observations by incorporating climatological information on the depths of the euphotic zone and the mixed layer that control the distribution of phytoplankton that significantly improved the fidelity of satellite derived PP to in situ observations. The annual IPP of the Arctic Ocean combining both in situ and satellite based estimates was calculated here to be a minimum of 466 ± 94 Tg C yr-1 and a maximum of 993 ± 94 Tg C yr-1, when corrected for subsurface production. Inflow shelf seas account for 75% of annual IPP, while the central basin and Beaufort northern sea were the regions with the lowest annual integrated productivity, due to persistently stratified, oligotrophic and ice-covered conditions. Although the expansion of summertime

Secondary organic aerosols over oceans via oxidation of isoprene and monoterpenes from Arctic to Antarctic.

PubMed

Hu, Qi-Hou; Xie, Zhou-Qing; Wang, Xin-Ming; Kang, Hui; He, Quan-Fu; Zhang, Pengfei

2013-01-01

Isoprene and monoterpenes are important precursors of secondary organic aerosols (SOA) in continents. However, their contributions to aerosols over oceans are still inconclusive. Here we analyzed SOA tracers from isoprene and monoterpenes in aerosol samples collected over oceans during the Chinese Arctic and Antarctic Research Expeditions. Combined with literature reports elsewhere, we found that the dominant tracers are the oxidation products of isoprene. The concentrations of tracers varied considerably. The mean average values were approximately one order of magnitude higher in the Northern Hemisphere than in the Southern Hemisphere. High values were generally observed in coastal regions. This phenomenon was ascribed to the outflow influence from continental sources. High levels of isoprene could emit from oceans and consequently have a significant impact on marine SOA as inferred from isoprene SOA during phytoplankton blooms, which may abruptly increase up to 95 ng/m³ in the boundary layer over remote oceans.

NABOS-II Observational Program in the Arctic Ocean: New Perspectives and New Challenges

NASA Astrophysics Data System (ADS)

Ivanov, V.; Polyakov, I.; Ashik, I. M.; Pnyushkov, A.; Alkire, M. B.; Repina, I.; Alexeev, V. A.; Waddington, I.; Kanzow, T.; Goszczko, I.; Rember, R.; Artamonov, A.

2016-02-01

NABOS-II observational program was launched in 2013 on the basis of new knowledge obtained during NABOS (=Nansen and Amundsen Basins Observations System) project back in 2000s. Up to now two large scale expeditions in the Eurasian sector of the Arctic Ocean were carried out in framework of NABOS-II: in 2013 and in 2015. These field studies were conducted by International Arctic Research Center (IARC) University of Alaska Fairbanks, USA in partnership with Arctic and Antarctic Research Institute (AARI) St.Petersburg Russia. The main goal of the NABOS-II project is to provide quantitative assessment of circulation and water mass transformation along the principal pathways transporting water from the Nordic Seas to the Arctic Basin under conditions of substantially reduced summer ice cover. Reduced sea ice causes changes in the water column and in the overlying atmosphere. Documenting of these changes was the main target of the NABOS-II cruises. The scope of this goal and the opportunities of extended scientific research in the Arctic, provided during NABOS expeditions, encouraged scientific institutions from the USA, Europe and Asia to raise funds, contribute to the cruise program and to send their personnel to expeditions, thus giving them a true multidisciplinary status. The ambitious mission of collecting a two year long time series of hydrographic data at 6 moorings along 126E meridian from the upper slope (250 m depth) to the deep basin (3900 m depth) in the Laptev Sea was successfully accomplished in 2015. The collected data are truly unique, since they shed new light on the structure and spatio-temporal variability of water properties and transports in the Lapev Sea, which is the key region for understanding of interaction between Atlantic water branches. This presentation describes preliminary results of performed analysis.

NABOS-II Observational Program in the Arctic Ocean: New Perspectives and new Challenges

NASA Astrophysics Data System (ADS)

Ivanov, Vladimir; Polyakov, Igor; Ashik, Igor; Pnyushkov, Andrey; Alkire, Matthew; Repina, Irina; Alexeev, Vladimir; Waddington, Ian; Kanzow, Torsten; Rember, Robert; Artamonov, Alexander; Goszczko, Ilona

2016-04-01

NABOS-II observational program was launched in 2013 on the basis of new knowledge obtained during NABOS (=Nansen and Amundsen Basins Observations System) project back in 2000s. Up to now two large scale expeditions in the Eurasian sector of the Arctic Ocean were carried out in framework of NABOS-II: in 2013 and in 2015. These field studies were conducted by International Arctic Research Center (IARC) University of Alaska Fairbanks, USA in partnership with Arctic and Antarctic Research Institute (AARI) St.Petersburg Russia. The main goal of the NABOS-II project is to provide quantitative assessment of circulation and water mass transformation along the principal pathways transporting water from the Nordic Seas to the Arctic Basin under conditions of substantially reduced summer ice cover. Reduced sea ice causes changes in the water column and in the overlying atmosphere. Documenting of these changes was the main target of the NABOS-II cruises. The scope of this goal and the opportunities of extended scientific research in the Arctic, provided during NABOS expeditions, encouraged scientific institutions from the USA, Europe and Asia to raise funds, contribute to the cruise program and to send their personnel to expeditions, thus giving them a true multidisciplinary status. The ambitious mission of collecting a two year long time series of hydrographic data at 6 moorings along 126E meridian from the upper slope (250 m depth) to the deep basin (3900 m depth) in the Laptev Sea was successfully accomplished in 2015. The collected data are truly unique, since they shed new light on the structure and spatio-temporal variability of water properties and transports in the Lapev Sea, which is the key region for understanding of interaction between Atlantic water branches. This presentation describes preliminary results of performed analysis.

Circum-arctic plate accretion - Isolating part of a pacific plate to form the nucleus of the Arctic Basin

USGS Publications Warehouse

Churkin, M.; Trexler, J.H.

1980-01-01

A mosaic of large lithospheric plates rims the Arctic Ocean Basin, and foldbelts between these plates contain numerous allochthonous microplates. A new model for continental drift and microplate accretion proposes that prior to the late Mesozoic the Kula plate extended from the Pacific into the Arctic. By a process of circumpolar drift and microplate accretion, fragments of the Pacific basin, including parts of the Kula plate, were cut off and isolated in the Arctic Ocean, the Yukon-Koyukuk basin in Alaska, and the Bering Sea. ?? 1980.

Sea ice thermohaline dynamics and biogeochemistry in the Arctic Ocean: Empirical and model results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duarte, Pedro; Meyer, Amelie; Olsen, Lasse M.

Here, large changes in the sea ice regime of the Arctic Ocean have occurred over the last decades justifying the development of models to forecast sea ice physics and biogeochemistry. The main goal of this study is to evaluate the performance of the Los Alamos Sea Ice Model (CICE) to simulate physical and biogeochemical properties at time scales of a few weeks and to use the model to analyze ice algal bloom dynamics in different types of ice. Ocean and atmospheric forcing data and observations of the evolution of the sea ice properties collected from 18 April to 4 Junemore » 2015, during the Norwegian young sea ICE expedition, were used to test the CICE model. Our results show the following: (i) model performance is reasonable for sea ice thickness and bulk salinity; good for vertically resolved temperature, vertically averaged Chl a concentrations, and standing stocks; and poor for vertically resolved Chl a concentrations. (ii) Improving current knowledge about nutrient exchanges, ice algal recruitment, and motion is critical to improve sea ice biogeochemical modeling. (iii) Ice algae may bloom despite some degree of basal melting. (iv) Ice algal motility driven by gradients in limiting factors is a plausible mechanism to explain their vertical distribution. (v) Different ice algal bloom and net primary production (NPP) patterns were identified in the ice types studied, suggesting that ice algal maximal growth rates will increase, while sea ice vertically integrated NPP and biomass will decrease as a result of the predictable increase in the area covered by refrozen leads in the Arctic Ocean.« less

Sea ice thermohaline dynamics and biogeochemistry in the Arctic Ocean: Empirical and model results

DOE PAGES

Duarte, Pedro; Meyer, Amelie; Olsen, Lasse M.; ...

2017-06-08

Here, large changes in the sea ice regime of the Arctic Ocean have occurred over the last decades justifying the development of models to forecast sea ice physics and biogeochemistry. The main goal of this study is to evaluate the performance of the Los Alamos Sea Ice Model (CICE) to simulate physical and biogeochemical properties at time scales of a few weeks and to use the model to analyze ice algal bloom dynamics in different types of ice. Ocean and atmospheric forcing data and observations of the evolution of the sea ice properties collected from 18 April to 4 Junemore » 2015, during the Norwegian young sea ICE expedition, were used to test the CICE model. Our results show the following: (i) model performance is reasonable for sea ice thickness and bulk salinity; good for vertically resolved temperature, vertically averaged Chl a concentrations, and standing stocks; and poor for vertically resolved Chl a concentrations. (ii) Improving current knowledge about nutrient exchanges, ice algal recruitment, and motion is critical to improve sea ice biogeochemical modeling. (iii) Ice algae may bloom despite some degree of basal melting. (iv) Ice algal motility driven by gradients in limiting factors is a plausible mechanism to explain their vertical distribution. (v) Different ice algal bloom and net primary production (NPP) patterns were identified in the ice types studied, suggesting that ice algal maximal growth rates will increase, while sea ice vertically integrated NPP and biomass will decrease as a result of the predictable increase in the area covered by refrozen leads in the Arctic Ocean.« less

Sea ice thermohaline dynamics and biogeochemistry in the Arctic Ocean: Empirical and model results

NASA Astrophysics Data System (ADS)

Duarte, Pedro; Meyer, Amelie; Olsen, Lasse M.; Kauko, Hanna M.; Assmy, Philipp; Rösel, Anja; Itkin, Polona; Hudson, Stephen R.; Granskog, Mats A.; Gerland, Sebastian; Sundfjord, Arild; Steen, Harald; Hop, Haakon; Cohen, Lana; Peterson, Algot K.; Jeffery, Nicole; Elliott, Scott M.; Hunke, Elizabeth C.; Turner, Adrian K.

2017-07-01

Large changes in the sea ice regime of the Arctic Ocean have occurred over the last decades justifying the development of models to forecast sea ice physics and biogeochemistry. The main goal of this study is to evaluate the performance of the Los Alamos Sea Ice Model (CICE) to simulate physical and biogeochemical properties at time scales of a few weeks and to use the model to analyze ice algal bloom dynamics in different types of ice. Ocean and atmospheric forcing data and observations of the evolution of the sea ice properties collected from 18 April to 4 June 2015, during the Norwegian young sea ICE expedition, were used to test the CICE model. Our results show the following: (i) model performance is reasonable for sea ice thickness and bulk salinity; good for vertically resolved temperature, vertically averaged Chl a concentrations, and standing stocks; and poor for vertically resolved Chl a concentrations. (ii) Improving current knowledge about nutrient exchanges, ice algal recruitment, and motion is critical to improve sea ice biogeochemical modeling. (iii) Ice algae may bloom despite some degree of basal melting. (iv) Ice algal motility driven by gradients in limiting factors is a plausible mechanism to explain their vertical distribution. (v) Different ice algal bloom and net primary production (NPP) patterns were identified in the ice types studied, suggesting that ice algal maximal growth rates will increase, while sea ice vertically integrated NPP and biomass will decrease as a result of the predictable increase in the area covered by refrozen leads in the Arctic Ocean.

K-Rich Basaltic Sources beneath Ultraslow Spreading Central Lena Trough in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Ling, X.; Snow, J. E.; Li, Y.

2016-12-01

Magma sources fundamentally influence accretion processes at ultraslow spreading ridges. Potassium enriched Mid-Ocean Ridge Basalt (K-MORB) was dredged from the central Lena Trough (CLT) in the Arctic Ocean (Nauret et al., 2011). Its geochemical signatures indicate a heterogeneous mantle source with probable garnet present under low pressure. To explore the basaltic mantle sources beneath the study area, multiple models are carried out predicting melting sources and melting P-T conditions in this study. P-T conditions are estimated by the experimental derived thermobarometer from Hoang and Flower (1998). Batch melting model and major element model (AlphaMELTs) are used to calculate the heterogeneous mantle sources. The modeling suggests phlogopite is the dominant H2O-K bearing mineral in the magma source. 5% partial melting of phlogopite and amphibole mixing with depleted mantle (DM) melt is consistent with the incompatible element pattern of CLT basalt. P-T estimation shows 1198-1212oC/4-7kbar as the possible melting condition for CLT basalt. Whereas the chemical composition of north Lena Trough (NLT) basalt is similar to N-MORB, and the P-T estimation corresponds to 1300oC normal mantle adiabat. The CLT basalt bulk composition is of mixture of 40% of the K-MORB endmember and an N-MORB-like endmember similar to NLT basalt. Therefore the binary mixing of the two endmembers exists in the CLT region. This kind of mixing infers to the tectonic evolution of the region, which is simultaneous to the Arctic Ocean opening.

An Ocean Basin of Dirt? Using Molecular Biomarkers and Radiocarbon to Identify Organic Carbon Sources and their Preservation in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Harvey, H.; Belicka, L. L.

2005-12-01

In the modern Arctic Ocean, primary production in waters over the broad continental shelves and under ice contributes an estimated 250 Mt/yr of POC to Arctic waters. The delivery of terrestrial material from large rivers, ice transport and through coastal erosion adds at least an additional 12 Mt/yr of POC. Although the marine organic carbon signal in Arctic Ocean exceeds that of terrestrial carbon by an order or magnitude or more, recent evidence suggests that this balance is not maintained and significant fractions of terrestrial carbon is preserved in sediments. Using an integrated approach combining lipid biomarkers and radiocarbon dating in particles and sediments, the process of organic carbon recycling and historical changes in its sources and preservation has been examined. A suite of lipid biomarkers in particles and sediments of western Arctic shelves and basins were measured and principle components analysis (PCA) used to allow a robust comparison among the 120+ individual compounds to assign organic sources and relative inputs. Offshore particles from the chlorophyll maximum contained abundant algal markers (e.g. 20:5 and 22:6 FAMEs), low concentrations of terrestrial markers (amyrins and 24-ethylcholest-5-en-3b-ol), and reflected modern 14C values. Particles present in deeper halocline waters also reflect marine production, but a portion of older, terrestrial carbon accompanies the sinking of the spring bloom. Surface and deeper sediments of basins contain older organic carbon and low concentrations of algal biomarkers, suggesting that marine carbon produced in surface waters is rapidly recycled. Taken together, these observations suggest that marine derived organic matter produced in shallow waters fuels carbon cycling, but relatively small amounts are preserved in sediments. As a result, the organic carbon preserved in sediments contrasts sharply to that typically observed in lower latitudes, with an increasing terrestrial signature with distance

The Need and Opportunity for an Integrated Research, Development and Testing Station in the Alaskan High Arctic

NASA Astrophysics Data System (ADS)

Hardesty, J. O.; Ivey, M.; Helsel, F.; Dexheimer, D.; Cahill, C. F.; Bendure, A.; Lucero, D. A.; Roesler, E. L.

2016-12-01

This presentation will make the case for development of a permanent integrated research and testing station at Oliktok Point, Alaska; taking advantage of existing assets and infrastructure, controlled airspace, an active UAS program and local partnerships. Arctic research stations provide critical monitoring and research on climate change for conditions and trends in the Arctic. The US Chair of the Arctic Council has increased awareness of gaps in our understanding of Artic systems, scarce monitoring, lack of infrastructure and readiness for emergency response. Less sea ice brings competition for commercial shipping and resource extraction. Search and rescue, pollution mitigation and safe navigation need real-time, wide-area monitoring to respond to events. Multi-national responses for international traffic will drive a greater security presence to protect citizens and sovereign interests. To address research and technology gaps, there is a national need for a High Arctic Station with an approach that partners stakeholders from science, safety and security to develop comprehensive solutions. The Station should offer year-round use, logistic support and access to varied ecological settings; phased adaptation to changing needs; and support testing of technologies such as multiple autonomous platforms, renewable energies and microgrids, and sensors in Arctic settings. We propose an Arctic Station at Oliktok Point, Alaska. Combined with the Toolik Field Station and Barrow Environmental Observatory, they form a US network of Arctic Stations. An Oliktok Point Station can provide complementary and unique assets that include: ocean access, and coastal and terrestrial systems; road access; controlled airspaces on land and ocean; nearby air facilities, medical and logistic support; atmospheric observations from an adjacent ARM facility; connections to Barrow and Toolik; fiber-optic communications; University of Alaska Fairbanks UAS Test Facility partnership; and an airstrip

Using the Environmental Intelligence Framework to Address Arctic Issues: A Case Study of Alaskan Fisheries and Ocean Acidification

NASA Astrophysics Data System (ADS)

Mathis, J. T.; Osborne, E.; Bamzai, A. S.; Starkweather, S.

2017-12-01

Profound environmental change in the Arctic region is driving an urgent need for faster and more efficient knowledge creation and delivery for residents of the Arctic as well as stakeholders around the globe. The overarching issues at play include environmental stewardship, community health and cultural survival. To effectively address these issues, the Interagency Arctic Research Policy Committee (IAPRC) recently established the Environmental Intelligence Collaboration Team (EICT) that integrates observing capabilities, modelling efforts and data management. Since its inception, the EICT has been working to create pathways to environmental knowledge that sustains end-to-end integration of research across the linked steps of data integration, environmental observing, predictive modelling, assessing responsiveness to stakeholder needs and ultimately providing decision support. The EICT is currently focusing on the carbon-climate aspect of environmental knowledge and identifing specific decision-making needs to meet policy goals for topics such as carbon emissions from permafrost thaw, increasing wildfire frequency and ocean acidification. As a case study, we applied the Environmental Intelligence framework to understanding the effects of ocean acidification in southern Alaska where there are critical commercial and subsistence fisheries. The results of this work revealed that there is currently a 5-month window of optimal growing conditions at a hatchery facility for many juvenile shellfish although that window is expected to close by 2040. The outcome of this work relates directly to fisheries management decisions and identifies the need for continued Environmental Intelligence collection to monitor and mitigate ocean acidification in the Alaskan region.

An analysis of the carbon balance of the Arctic Basin from 1997 to 2006

Treesearch

A.D. McGuire; D.J. Hayes; D.W. Kicklighter; M. Manizza; Q. Zhuang; M. Chen; M.J. Follows; K.R. Gurney; J.W. McClelland; J.M. Melillo; B.J. Peterson; R.G. Prinn

2010-01-01

This study used several model-based tools to analyze the dynamics of the Arctic Basin between 1997 and 2006 as a linked system of land-ocean-atmosphere C exchange. The analysis estimates that terrestrial areas of the Arctic Basin lost 62.9 Tg C yr-1 and that the Arctic Ocean gained 94.1 Tg C yr-1. Arctic lands and oceans...

A tale of two basins: An integrated physical and biological perspective of the deep Arctic Ocean

NASA Astrophysics Data System (ADS)

Bluhm, B. A.; Kosobokova, K. N.; Carmack, E. C.

2015-12-01

domains have vertical stratification that constrains the transfer of nutrients to the surface layer (euphotic zone), thus leading to their oligotrophic state, particularly in the more strongly stratified Pacific Arctic where, despite high nutrient values in the inflow, convective reset of surface layer nutrients by haline convection in winter is virtually absent. First and multi-year sea ice drastically alters albedo and insulates the underlying water column from extreme winter heat loss while its mechanical properties (thickness, concentration, roughness, etc.) greatly affect the efficiency of momentum transfer from the wind to the underlying water. Biologically, sea ice algal growth in the basins is proportionally almost equal to or exceeding phytoplankton production, and is a habitat and transport platform for sympagic (ice-associated) fauna. Owing to nutrient limitation due to strong stratification and light limitation due to snow and ice cover and extreme sun angle, primary production in the two basin domains is very low compared to the adjacent shelves. Severe nutrient limitation and complete euphotic zone drawdown in the AB favors small phytoplankton, a ubiquitous deep chlorophyll maximum layer, a low f-ratio of new to recycled carbon fixation, and a low energy food web. In contrast, nutrients persist -albeit in low levels- in the western EB, even in summer, suggesting light limitation, heavy grazing or both. The higher stocks of nutrients in the EB are more conducive to marginal ice blooms than in the AB. The large-scale ocean currents (NHTC and ACBC) import substantial expatriate, not locally reproducing zooplankton biomass especially from the adjoining subarctic Atlantic (primarily Calanus finmarchicus), but also from the Pacific (e.g., Pseudocalanus spp., Neocalanus spp. and Metridia pacifica). These advective inputs serve both as source of food to resident pelagic and benthic biota within the basins, and as potential grazers exerting top down control on

Amplified Arctic warming by phytoplankton under greenhouse warming.

PubMed

Park, Jong-Yeon; Kug, Jong-Seong; Bader, Jürgen; Rolph, Rebecca; Kwon, Minho

2015-05-12

Phytoplankton have attracted increasing attention in climate science due to their impacts on climate systems. A new generation of climate models can now provide estimates of future climate change, considering the biological feedbacks through the development of the coupled physical-ecosystem model. Here we present the geophysical impact of phytoplankton, which is often overlooked in future climate projections. A suite of future warming experiments using a fully coupled ocean-atmosphere model that interacts with a marine ecosystem model reveals that the future phytoplankton change influenced by greenhouse warming can amplify Arctic surface warming considerably. The warming-induced sea ice melting and the corresponding increase in shortwave radiation penetrating into the ocean both result in a longer phytoplankton growing season in the Arctic. In turn, the increase in Arctic phytoplankton warms the ocean surface layer through direct biological heating, triggering additional positive feedbacks in the Arctic, and consequently intensifying the Arctic warming further. Our results establish the presence of marine phytoplankton as an important potential driver of the future Arctic climate changes.

Downscaling ocean conditions with application to the Gulf of Maine, Scotian Shelf and adjacent deep ocean

NASA Astrophysics Data System (ADS)

Katavouta, Anna; Thompson, Keith

2017-04-01

A high resolution regional model (1/36 degree) of the Gulf of Maine, Scotian Shelf and adjacent deep ocean (GoMSS) is developed to downscale ocean conditions from an existing global operational system. First, predictions from the regional GoMSS model in a one-way nesting set up are evaluated using observations from multiple sources including satellite-borne sensors of surface temperature and sea level, CTDs, Argo floats and moored current meters. It is shown that on the shelf, the regional model predicts more realistic fields than the global system because it has higher resolution and includes tides that are absent from the global system. However, in deep water the regional model misplaces deep ocean eddies and meanders associated with the Gulf Stream. This is because of unrealistic internally generated variability (associated with the one-way nesting set up) that leads to decoupling of the regional model from the global system in the deep water. To overcome this problem, the large scales (length scales > 90 km) of the regional model are spectrally nudged towards the global system fields. This leads to more realistic predictions off the shelf. Wavenumber spectra show that even though spectral nudging constrains the large scales, it does not suppress the variability on small scales; on the contrary, it favours the formation of eddies with length scales below the cut-off wavelength of the spectral nudging.

Structural-tectonic zoning of the Arctic

NASA Astrophysics Data System (ADS)

Petrov, Oleg; Sobolev, Nikolay; Morozov, Andrey; Shokalsky, Sergey; Kashubin, Sergey; Grikurov, Garrik; Tolmacheva, Tatiana; Rekant, Pavel; Petrov, Evgeny

2017-04-01

Structural-tectonic zoning of the Arctic is based on the processing of geological and geophysical data and bottom sampling materials produced within the project "Atlas of Geological Maps of the Circumpolar Arctic." Zoning of the Arctic territories has been conducted taking into account the Earth's crust types, age of consolidated basement, and features of geological structure of the sedimentary cover. Developed legend for the zoning scheme incorporates five main groups of elements: continental and oceanic crust, folded platform covers, accretion-collision systems, and provinces of continental cover basalts. An important feature of the structural-tectonic zoning scheme is designation of continental crust in the central regions of the Arctic Ocean, the existence of which is assumed on the basis of numerous geological data. It has been found that most of the Arctic region has continental crust with the exception of the Eurasian Basin and the central part of the Canada Basin, which are characterized by oceanic crust type. Thickness of continental crust from seismic data varies widely: from 30-32 km on the Mendeleev Rise to 18-20 km on the Lomonosov Ridge, decreasing to 8-10 km in rift structures of the Podvodnikov-Makarov Basin at the expense of reduction of the upper granite layer. New data confirm similar basement structure on the western and eastern continental margins of the Eurasian oceanic basin. South to north, areas of Neoproterozoic (Baikalian) and Paleozoic (Ellesmerian) folding are successively distinguished. Neoproterozoic foldbelt is observed in Central Taimyr (Byrranga Mountains). Continuation of this belt in the eastern part of the Arctic is Novosibirsk-Chukchi fold system. Ellesmerian orogen incorporates the northernmost areas of Taimyr and Severnaya Zemlya, wherefrom it can be traced to the Geofizikov Spur of the Lomonosov Ridge and further across the De Long Archipelago and North Chukchi Basin to the north of Alaska Peninsula and in the Beaufort Sea

An Array of Ice-Based Observatories for Arctic Studies

NASA Astrophysics Data System (ADS)

Plueddemann, A.; Proshutinsky, A.; Toole, J.; Ashjian, C.; Krishfield, R.; Carmack, E.; Dethloff, K.; Fahrbach, E.; Gascard, J.; Perovich, D.; Pryamikov, S.

2004-12-01

The Arctic Ocean's role in global climate - while now widely appreciated - remains poorly understood. Lack of information about key processes within the oceanic, cryospheric, biologic, atmospheric and geologic disciplines will continue to impede physical understanding, model validation, and climate prediction until a practical observing system is designed and implemented. Requirements, challenges and recommendations for Ice-Based Observatories (IBO?s) for the Arctic Ocean were formulated by workshop participants of an international workshop entitled "Arctic Observing Based on Ice-Tethered Platforms" held at the Woods Hole Oceanographic Institution in Woods Hole, Massachusetts, USA, June 28-30, 2004. The principal conclusion from the workshop was that practical, cost-effective and proven IBO designs presently exist, can be readily extended to provide interdisciplinary observations, and should be implemented expeditiously as part of a coordinated Arctic observing system. Ice-based instrument systems are a proven means of acquiring unattended high quality air, ice, and ocean data from the central Arctic during all seasons. Arctic Change is ongoing and measurements need to begin now. An array of approximately 25-30 IBO units maintained throughout the Arctic Ocean is envisioned to observe the annual and interannual variations of the polar atmosphere-ice-ocean environment. An international body will be required to coordinate the various national programs (eliminate overlap, insure no data holes) and insure compatibility of data and their widespread distribution. A long-term, internationally coordinated logistics plan should be implemented as an essential complement to scientific and technical plans for an IBO array. The 25 years of IABP drift trajectories, existing data climatologies and available numerical simulations should be exploited to derive insight to optimal array design, deployment strategies, sampling intervals, and expected performance of an IBO array. IBO

Giant caldera in the Arctic Ocean: Evidence of the catastrophic eruptive event.

PubMed

Piskarev, Alexey; Elkina, Daria

2017-04-10

A giant caldera located in the eastern segment of the Gakkel Ridge could be firstly seen on the bathymetric map of the Arctic Ocean published in 1999. In 2014, seismic and multibeam echosounding data were acquired at the location. The caldera is 80 km long, 40 km wide and 1.2 km deep. The total volume of ejected volcanic material is estimated as no less than 3000 km 3 placing it into the same category with the largest Quaternary calderas (Yellowstone and Toba). Time of the eruption is estimated as ~1.1 Ma. Thin layers of the volcanic material related to the eruption had been identified in sedimentary cores located about 1000 km away from the Gakkel Ridge. The Gakkel Ridge Caldera is the single example of a supervolcano in the rift zone of the Mid-Oceanic Ridge System.

Giant caldera in the Arctic Ocean: Evidence of the catastrophic eruptive event

PubMed Central

Piskarev, Alexey; Elkina, Daria

2017-01-01

A giant caldera located in the eastern segment of the Gakkel Ridge could be firstly seen on the bathymetric map of the Arctic Ocean published in 1999. In 2014, seismic and multibeam echosounding data were acquired at the location. The caldera is 80 km long, 40 km wide and 1.2 km deep. The total volume of ejected volcanic material is estimated as no less than 3000 km3 placing it into the same category with the largest Quaternary calderas (Yellowstone and Toba). Time of the eruption is estimated as ~1.1 Ma. Thin layers of the volcanic material related to the eruption had been identified in sedimentary cores located about 1000 km away from the Gakkel Ridge. The Gakkel Ridge Caldera is the single example of a supervolcano in the rift zone of the Mid-Oceanic Ridge System. PMID:28393928

Climate sensitivity to Arctic seaway restriction during the early Paleogene

NASA Astrophysics Data System (ADS)

Roberts, Christopher D.; LeGrande, Allegra N.; Tripati, Aradhna K.

2009-09-01

The opening and closing of ocean gateways affects the global distribution of heat, salt, and moisture, potentially driving climatic change on regional to global scales. Between 65 and 45 million years ago (Ma), during the early Paleogene, exchange between the Arctic and global oceans occurred through two narrow and shallow seaways, the Greenland-Norway seaway and the Turgai Strait. Sediments from the Arctic Ocean suggest that, during this interval, the surface ocean was warm, brackish, and episodically enabled the freshwater fern Azolla to bloom. The precise mechanisms responsible for the development of these conditions in the Paleogene Arctic remain uncertain. Here we show results from an isotope-enabled, atmosphere-ocean general circulation model, which indicate that Northern Hemisphere climate would have been very sensitive to the degree of oceanic exchange through the Arctic seaways. We also present modelled estimates of seawater and calcite δ18O for the Paleogene. By restricting these seaways, we simulate freshening of the surface Arctic Ocean to ~ 6 psu and warming of sea-surface temperatures by 2 °C in the North Atlantic and 5-10 °C in the Labrador Sea. Our results may help explain the occurrence of low-salinity tolerant taxa in the Arctic Ocean during the Eocene and provide a mechanism for enhanced warmth in the north western Atlantic. We propose that the formation of a volcanic land-bridge between Greenland and Europe could have caused increased ocean convection and warming of intermediate waters in the Atlantic. If true, this result is consistent with the theory that bathymetry changes may have caused thermal destabilisation of methane clathrates and supports a tectonic trigger hypothesis for the Paleocene Eocene Thermal Maximum (PETM).

Does the Arctic Amplification peak this decade?

NASA Astrophysics Data System (ADS)

Martin, Torge; Haine, Thomas W. N.

2017-04-01

Temperatures rise faster in the Arctic than on global average, a phenomenon known as Arctic Amplification. While this is well established from observations and model simulations, projections of future climate (here: RCP8.5) with models of the Coupled Model Intercomparison Project phase 5 (CMIP5) also indicate that the Arctic Amplification has a maximum. We show this by means of an Arctic Amplification factor (AAF), which we define as the ratio of Arctic mean to global mean surface air temperature (SAT) anomalies. The SAT anomalies are referenced to the period 1960-1980 and smoothed by a 30-year running mean. For October, the multi-model ensemble-mean AAF reaches a maximum in 2017. The maximum moves however to later years as Arctic winter progresses: for the autumn mean SAT (September to November) the maximum AAF is found in 2028 and for winter (December to February) in 2060. Arctic Amplification is driven, amongst others, by the ice-albedo feedback (IAF) as part of the more general surface albedo feedback (involving clouds, snow cover, vegetation changes) and temperature effects (Planck and lapse-rate feedbacks). We note that sea ice retreat and the associated warming of the summer Arctic Ocean are not only an integral part of the IAF but are also involved in the other drivers. In the CMIP5 simulations, the timing of the AAF maximum coincides with the period of fastest ice retreat for the respective month. Presence of at least some sea ice is crucial for the IAF to be effective because of the contrast in surface albedo between ice and open water and the need to turn ocean warming into ice melt. Once large areas of the Arctic Ocean are ice-free, the IAF should be less effective. We thus hypothesize that the ice retreat significantly affects AAF variability and forces a decline of its magnitude after at least half of the Arctic Ocean is ice-free and the ice cover becomes basically seasonal.

Loss of sea ice in the Arctic.

PubMed

Perovich, Donald K; Richter-Menge, Jacqueline A

2009-01-01

The Arctic sea ice cover is in decline. The areal extent of the ice cover has been decreasing for the past few decades at an accelerating rate. Evidence also points to a decrease in sea ice thickness and a reduction in the amount of thicker perennial sea ice. A general global warming trend has made the ice cover more vulnerable to natural fluctuations in atmospheric and oceanic forcing. The observed reduction in Arctic sea ice is a consequence of both thermodynamic and dynamic processes, including such factors as preconditioning of the ice cover, overall warming trends, changes in cloud coverage, shifts in atmospheric circulation patterns, increased export of older ice out of the Arctic, advection of ocean heat from the Pacific and North Atlantic, enhanced solar heating of the ocean, and the ice-albedo feedback. The diminishing Arctic sea ice is creating social, political, economic, and ecological challenges.

Simulating the natural variability of the freshwater budget of the Arctic ocean from the mid to late Holocene using LOVECLIM

NASA Astrophysics Data System (ADS)

Davies, F. J.; Goosse, H.; Renssen, H.

2012-04-01

The influence of freshwater on the long term climatic variability of the Arctic region is currently of significant interest. Alterations to the natural variability of the oceanic, terrestrial and atmospheric sources of freshwater to the Arctic ocean, caused by anthropogenic induced warming, are likely to have far reaching effects on oceanic processes and climate. A number of these changes are already observable, such as an intensification of the hydrological cycle, a 7% increase in Eurasian river runoff (1936-1999), a 9% reduction of sea-ice extent per decade (1979-2006), a 120km northward migration of permafrost in Northern Canada (1968-1994), and air temperatures 6°C warmer, in parts, from 2007 to 2010, when compared to the 1958-1996 average. All of these changes add another layer of complexity to understanding the role of the freshwater budget, and this makes it difficult to say with any certainty how these future changes will impact freshwater fluxes of the Arctic gateways, such as the Bering Strait, Fram Strait, Canadian Arctic Archipelago and the Barents Sea inflow. Despite these difficulties, there have been studies that have integrated the available data, from both in situ measurements and modelling studies, and used this as a basis to form a picture of the current freshwater budget, and then project upon these hypotheses for the future (Holland et al., 2007). However, one particular aspect of these future projections that is lacking is the accountability of how much future variance is attributable to both natural variability and anthropogenic influences. Here we present results of a mid to late (6-0ka) Holocene transient simulation, using the earth model of intermediate complexity, LOVECLIM (Goosse et al., 2010). The model is forced with orbital and greenhouse gas forcings appropriate for the time period. The results will highlight the natural variability of the oceanic, terrestrial and atmospheric components of the freshwater budget, over decadal and

Alkenone-based reconstructions reveal four-phase Holocene temperature evolution for High Arctic Svalbard

NASA Astrophysics Data System (ADS)

van der Bilt, Willem G. M.; D'Andrea, William J.; Bakke, Jostein; Balascio, Nicholas L.; Werner, Johannes P.; Gjerde, Marthe; Bradley, Raymond S.

2018-03-01

Situated at the crossroads of major oceanic and atmospheric circulation patterns, the Arctic is a key component of Earth's climate system. Compounded by sea-ice feedbacks, even modest shifts in the region's heat budget drive large climate responses. This is highlighted by the observed amplified response of the Arctic to global warming. Assessing the imprint and signature of underlying forcing mechanisms require paleoclimate records, allowing us to expand our knowledge beyond the short instrumental period and contextualize ongoing warming. However, such datasets are scarce and sparse in the Arctic, limiting our ability to address these issues. Here, we present two quantitative Holocene-length paleotemperature records from the High Arctic Svalbard archipelago, situated in the climatically sensitive Arctic North Atlantic. Temperature estimates are based on U37K unsaturation ratios from sediment cores of two lakes. Our data reveal a dynamic Holocene temperature evolution, with reconstructed summer lake water temperatures spanning a range of ∼6-8 °C, and characterized by four phases. The Early Holocene was marked by an early onset (∼10.5 ka cal. BP) of insolation-driven Hypsithermal conditions, likely compounded by strengthening oceanic heat transport. This warm interval was interrupted by cooling between ∼10.5-8.3 ka cal. BP that we attribute to cooling effects from the melting Northern Hemisphere ice sheets. Temperatures declined throughout the Middle Holocene, following a gradual trend that was accentuated by two cooling steps between ∼7.8-7 ka cal. BP and around ∼4.4-4.3 ka cal. BP. These transitions coincide with a strengthening influence of Arctic water and sea-ice in the adjacent Fram Strait. During the Late Holocene (past 4 ka), temperature change decoupled from the still-declining insolation, and fluctuated around comparatively cold mean conditions. By showing that Holocene Svalbard temperatures were governed by an alternation of forcings, this study

Utilizing chromophoric dissolved organic matter measurements to derive export and reactivity of dissolved organic carbon exported to the Arctic Ocean: A case study of the Yukon River, Alaska