Atlantic waters in the western arctic ocean
Download 2.02 Mb.
|
- Navigate this page:
- 2. PROPOSED WORK 2.1 Hypotheses
- Properties: H1
- Processes of Exchange: H1
- 2.2 Data sets and methods
- HYDROGRAPHIC/TRACER DATA MOORING DATA Historical
- Ongoing
- 2.3 Regional case studies 2.3a The Chukchi and Beaufort slopes and the interior Canada Basin
- Processes of exchange
- Shear zone north of the Alaskan Coast
- 2.3b The Chukchi Borderland and the Northwind Ridge
- Northwind Ridge enigma
- 2.3c The Makarov Basin and the Lincoln Sea
- (middle)
- Properties and processes
- 2.4 Pan-basin issues and overarching aims
- 2.5 Data products and archiving
- 2.7 Task distribution and time line Year 1
- 2.8. Timeliness and transformative potential
- 3. PRIOR WORK
- Education and Outreach
Theoretical advances: Recent work suggests two main candidates for the driving mechanism of the AW. Nazarenko et al., [1998] suggest eddy-topography interactions (the “Neptune” effect [Holloway, 1987; Polyakov, 2001]) is a dominant forcing, and obtain strongly topographically steered flows when using “Neptune” as a subgrid scale parameterization in an arctic primitive equation model. Nost and Isachsen [2003] propose instead the dominant driving is potential vorticity (PV) forcing along f/H contours (f is the Coriolis parameter, H is the ocean depth), which in polar regions dominantly follow H since f varies little. Some f/H contours are closed within the various arctic basins. Some circumnavigate the Arctic and are only completed in the Nordic Seas. This suggests that wind forcing in the Nordic Seas may drive the AW circulation in the Arctic. Building on results from a simple barotropic PV model [Yang, 2005], Karcher et al., [2007], consider the PV forcing of a density layer and, using a full primitive equation model, conclude the Barents Sea inflow through the St. Anna Trough is the critical forcing for AW circulation in the Arctic, although within the Canadian Basin local surface forcing (and the transfer of PV flux vertically) is equally (if not more) important and thus can determine the circulation of the interior Canadian Basin. Throughout the analysis, we will work closely with theoreticians (especially Holloway and Nost) and modelers, to seek insight from their results in the observations and to ensure that our data products are suitable for theory/model validation. For example, Nost’s work already produces the testable hypothesis that the core of the current will be found over f/H contours that exit through the Fram Strait, and that within the Canadian Basin, there is a cyclonic boundary flow and a weaker anticyclonic interior flow, and both Nost’s and Karcher’s studies suggest changes in the interior and boundary circulation under different regimes of the atmospheric Beaufort Gyre (strong and weak). 2. PROPOSED WORK 2.1 Hypotheses Our major goal is an observationally-based study of Atlantic Waters (AWs) in the Canadian Basin of the Arctic over the last two decades. Specifically, we will test the following hypotheses: Pathways: H1: The main circulation of AW is a cyclonic boundary current, following topographic pathways around the periphery of the Canadian Basin and along the major ridges. Outside the boundary current, flows are weak and variable. The basins contain AW eddies, fewer in number than Pacific Water eddies. H2: Canada Basin interior flow is anticyclonic, an extension of the surface Beaufort Gyre (thus north of Alaska, the interior flow is opposite to the boundary current). Makarov Basin interior flow is variable. Properties: H1: The boundary current is a strongly topographically steered, coherent current, equivalent barotropic in vertical structure, and is found over a set range of depth contours. H2: The boundary current velocities are a few cm/s and circulation within the Canadian Basin is ~ 2 Sv. (1 Sv=106m3/s). There are two main pathways - one circumnavigating the Canadian Basin, and one (smaller in volume) circumnavigating the Makarov Basin. Processes of Exchange: H1: The dominant exchange process between the boundary current and the interior is via double-diffusive interleaving. This exchange is a significant fraction of the boundary current flow and occurs along the length of the boundary current. A smaller role is played by eddies shed from the boundary current at specific locations (e.g., the north end of the Northwind Ridge). H2: Exchange with shelf waters is primarily though uplifting of AWs along topographic slopes and irregularities. Ventilation of the AWs by dense plumes of shelf-waters is much smaller. Our overarching aims are to describe and quantify circulation pathways and physical properties of AW throughout the Canadian Basin, and interactions between the boundary current and the interior flow. 2.2 Data sets and methods We propose to collate and collectively analyze historic observational data (hydrographic, chemistry, mooring, and drifting buoy data) from the Canadian Basin of the Arctic Ocean (see Table 1 for examples). The work has several initial regional focuses described below. The temporal focus is ~ 2 decades - the late 1980s to 2007, i.e., the start of International Polar Year (IPY) since these years (a) cover the conditions preceding and the transition to 1990s FSBW warming arrival in the western Arctic; and (b) have significant data so far uncollated or exploited. This work precedes the analysis of IPY data since preliminary work shows there is sufficient information in these decades to illuminate the issues discussed above, and thus provide valuable (urgent) guidance for the implementation of the Arctic Observing Network targeted for 2009, and (by providing a comprehensive historic background) will aid analysis of IPY data. Table 1: Examples of key modern data sets and models to be used in this study, with brief geographical and temporal description. All data are either publicly accessible or available to us via established collaborators. One product of our study will be a website listing all hydrographic data from the Canadian Basin, with links to publicly available data sets and contact information for non-public data sets.
Hydrographic sections are typically repeated only once a year. Thus aside from mooring data (which can address hourly to annual variability), we will concentrate on interannual variability. The baroclinic Rossby radius, frequently upheld as the necessary spatial resolution, is ~ 5-10 km in the Arctic. Variability on these space scales is observed over steep topography [e.g., Figure 4 of Woodgate et al., 2007], and observations from the Lomonosov Ridge and the Chukchi Borderland [Woodgate et al., 2001; Woodgate et al., 2007] suggest the width of the boundary current is several Rossby radii, order 50-100 km. Over the deep basins however, water properties vary on much longer (100-1000 kms) lengthscales, indeed one of the remarkable properties of the zigzags is their coherence across 1000s of km of the Arctic Ocean [Carmack et al., 1998]. Thus, we seek data sets with high spatial resolution over topography, but accept lower spatial resolution over the basins. Modern observations (e.g., CBL, SBI, and others) have the necessary high resolution surveys over the slopes. The SCICEX data are lower spatial resolution (~ 30 km), good for the basins, and adequate some purposes over the slopes if the structure of the zigzags are used to indicate whether the observation is in the core of the current. (Even if S data are low quality as in some SCICEX data, the zigzag form is evident just from T data, Figure 7.) Where possible, we will identify eddies from anomalous T-S and density values, and be alert to aliasing issues when data separation is large. Note, however, that although Pacific Water eddies are common in the Canadian Basin, AW eddies are (to date) far less frequently observed [D'Asaro, 1988; Woodgate et al., 2001]. We focus initially on regional studies, and then expand the work to a pan-basin perspective. For each region, we will use any available mooring data to study flow direction relative to local topography, using the best available topography, likely ship-survey data or IBCAO. (Frequently the principle axis of velocity variability aligns with topography, and we will use this as a proxy if topography is poorly known.) We will study along-slope and across slope velocity, and vertical structure of the flow. We will quantify variability as compared to the annual (or record length) mean, and check for statistically significant correlations with local wind or surface stress (using NCEP reanalysis data and fields from the UW Arctic Ocean model [Zhang, pers.comm.]). We will quantify tides and internal waves by standard techniques, and quantify eddy properties (e.g., rotation, magnitude) from T-S and velocity data, using e.g., hodographs [Foldvik et al., 1988; Woodgate et al., 2001; Lilly et al., 2003]. T-S variations over the mooring period (especially if combined with concurrent hydrographic data) also often indicate dominant physical processes such as mixing (straight lines in T-S space) or diffusive decay (smoothing in T-S space) [see e.g., Woodgate et al., 2001]. Using hydrographic data, we will map the T-maximum (FSBW) in the region and look for propagation of signals over multiple years. We will chart the heat content of both FSBW and BSBW. We will use zigzag structure to infer position within the boundary current, and newer and older water properties, and use the fingerprinting techniques to infer pathways [Woodgate et al., 2007]. We will use T-S analysis to suggest dominant physical processes (as per the mooring data). Using these analyses and any available tracer data (especially CFCs, oxygen and nutrients), we will bound the width and isobath range of the boundary current, and, with multiple years of data, estimate advection speeds. We will use hydrographic data to compute geostrophic velocity profiles, and where possible reference against layers of known motion (e.g., mooring data), and estimate volume transports and quantify exchanges. We will work closely with key arctic observationalists, theoreticians, and modelers. The hydrographic and mooring analyses are in collaboration with Ed Carmack, Fiona McLaughlin, and Koji Shimada. Interactions with theoreticians Greg Holloway and Ole Anders Nost will help guide required diagnostics from this study. We will also liaise closely with AOMIP modelers, to ensure the results are suitable for model verification. Finally, we will make results available to those planning the AON. 2.3 Regional case studies 2.3a The Chukchi and Beaufort slopes and the interior Canada Basin We will address first the important questions: (a) what is the interior AW circulation of the Canada Basin? and (b) what is the structure of the boundary current in the Canada Basin? These are urgent issues for model and theory development and for AON (for example, is the eastern Beaufort CABOS array sufficient for Canada Basin boundary current observations?). Pathways: To answer these questions, our first approach is the analysis of an underutilized set of moorings from the Beaufort slope and the central and eastern Canada Basin from the late 1980s and the 1990s (red dots in Figure 5, left panel). Preliminary studies of these data suggest an eastward boundary current over the slope and a weak flow in the basin, dominated by eddy features. Surprisingly, in the basin the simple record mean suggests a cyclonic interior flow, contrary to theoretical and some modeling expectations. We will study boundary current and interior flow properties as described above, using eddy analyses (such as hodographs) to ensure mean field is not contaminated by eddies. The 3 moorings of the Beaufort Gyre Project and the CABOS array also measure velocity, T and S in the AWs, and their results will be combined with this analysis. F  igure 5: (Left) Canada Basin mooring sites.
Beaufort Slope 1986-1988 & Central Beaufort 1990-1997, (red) 2-5 moorings a year (unpublished). CABOS, 2001-2007, 1 mooring a year (green). BGEP, 2003-present, 3-4 moorings a year (yellow). SBI 2002-2004 (8-9 mooring per year (cyan). (Right) Example of Canada Basin hydrographic (CTD/XCTD) station coverage (Oden, SCICEX, AOS, Polarstern, SHEBA, JOIS, NPEO, CBL, JWACS, BGEP, SBI, SW, Iceshelf, Melling, PolarStar) colored by year – black=pre-1991; red=1991-1995; magenta=1996-1997; blue=1998-2002; cyan=2003; green=2004-2005; yellow=2006-2007. Mooring locations marked as black dots with colored centers. Other relevant data sets (not shown) include Larsen, Mirai, Snowdragon, NOAA, Healy05Crossing, and drifting buoy data (e.g., IOEB, JCAD). Topography schematic, contoured at 500m. Note exact repeat lines are hidden by this representation. The mooring analysis will be combined with analysis of hydrographic data (Figure 5). From the large number of hydrographic sections extending north into the basin (including key repeat stations at ~ 150W and 140W), we will map progression over the last decades of the FSBW T-maximum, and FSBW and BSBW heat content, to assess advection of the FSBW warming (and possibly BSBW properties). Key to the slope analysis is to recognize which part of the boundary current is being sampled, and to address this we will examine tracer data (especially CFCs) and zigzag structure, using mapping techniques to infer boundary current pathways as described above [Woodgate et al., 2007]. When station coverage is sufficient, we will compute geostrophic velocities from CTD sections, referencing to mooring or buoy data where available or educated estimates of levels of known motion. Dynamic height calculations favor an anticyclonic AW circulation in the central Canadian Basin, similar to the surface anticylonic Beaufort Gyre [Worthington, 1959], but with a cyclonic eastward boundary flow over the Chukchi slope [Newton and Coachman, 1974]. Using data from several years, we will test these conclusions and study interannual variability. Since theories suggest that surface forcing influences the internal circulation, we will test for statistically significant correlations between in our inferred circulation and interannual variability in surface wind and surface stress. Properties: Published results (discussed above) suggest the boundary current structure over the Beaufort slope may differ significantly from that in the Eurasian and Makarov Basin. This may be due to different dominant physics (e.g. surface stress or lateral mixing) or sampling issues (e.g., are these data all from the same part of the boundary current?). Firstly, we will quantify flow structure in the mooring data available from the Beaufort Sea slope at several different locations (Figure 5). Secondly, from the hydrographic and mooring analysis, we will bound the isobath range of the boundary current, and assess how/if it varies interannually. We will use these results to assess which portion of the boundary current is being sampled by the mooring data. We anticipate this will yield information about the across-flow variability of the velocity structure of the boundary current. We will compare this across-flow variability to that found in geostrophic calculations. Our goal is to define the vertical structure of the boundary current, its isobath range and its horizontal width at key locations. This information is vital for AON to ensure that mooring sites will convey useful information about the boundary current variability and flow. Processes of exchange: We hypothesize 3 main processes of exchange – double diffusive intrusions, eddy transfer, and (to the shelf) slope upwelling. Firstly, we will map the spreading of zigzag structures into the basin over several years. If the zigzags were propagating perpendicular to the boundary current as per theory [McDougall, 1985], then assuming no flow in the interior, a repeat across-slope section may estimate spreading velocity. However, we hypothesize the interior flow is non-zero, and thus likely it advects zigzags either with or contrary to the boundary current. If so, the spreading patterns of zigzags may yield some indication of interior flow direction. For example, if the interior flow is cylonic and stronger than the boundary current, zigzags in the basin will progress around the gyre faster than those in the boundary current. If, however, the interior flow is anticyclonic (or cyclonic but slower than the boundary current), the basin zigzags will progress slower than the boundary current zigzags. Also, the zigzags are always a combination of boundary current and interior water, and the clear form of the zigzags in Figure 3 is likely a result of the interaction of two previously smooth T-S profiles. Thus, if zigzags structures are advected either with, or against the boundary current, subsequent double diffusive interaction with the boundary current could result in very complex structures. Although only qualitative, this type of analysis may suggest quantitative assessments. We will catalogue properties of AW eddies found in the mooring, CTD, and buoy data. Although eddies are formed by instabilities in Pacific Water flow entering the Arctic from the Chukchi Sea [D'Asaro, 1988; Pickart et al., 2005], given the low energy of the AW boundary current the most likely region of formation of AW eddies is the sharp topography of the northern Northwind Ridge. We will use T-S/tracer properties of eddies to seek possible regions of origin. Finally, we will use mooring and hydrographic data to assess shelf-slope exchange. Upwelling and mixing is known to occur along the Chukchi slope [Woodgate et al., 2005a] and along the Beaufort slope [Carmack and Kulikov, 1998] and is suggested to explain the slow propagation of the FSBW warming along the Beaufort slope [Shimada et al., 2004]. Ventilation of AW may also occur by plumes of dense shelf polynya waters [Aagaard et al., 1981; Weingartner et al., 1998]. Resultant T-S (and tracers) distinguishes these processes – polynya ventilation cools the upper AWs, whereas mixing forms warmer waters at those salinities [Woodgate et al., 2005a]. From T-S and tracer data over the slopes and deeper basin, we will use these methods to estimate the relative importance and ubiquity of these processes. Shear zone north of the Alaskan Coast: If the hypothesis of an interior flow contrary to the boundary current is correct, there must exist a (likely weak) velocity shear zone in the southern Beaufort Sea. Such a zone would have implications for mixing, exchange and relevance to ecosystems. Thus, seeking evidence of such a zone and defining its properties (e.g., permanence, depth range, surface expression, etc) is a possibly transformational aspect of our research. 2.3b The Chukchi Borderland and the Northwind Ridge Pathways: The Chukchi Borderland (CBL), a complex region of topographic ridges and abyssal plains consisting of the Siberian end of the Mendeleev Ridge, the Chukchi Rise, and the Northwind Ridge, offers many distinct routes to a topographically steered boundary current. For example the shallower part of the current may hug the continental slope south of the Chukchi Rise (and thus be involved in shelf processes), the deeper part may have to circumnavigate the Mendeleev Ridge, the Chukchi Rise and the Northwind Ridge, a substantially longer route. The dominant pathway will determine transit times and transformations of AW in this region. Propagation of the FSBW T-maximum, zigzags, and tracer data suggest the AW boundary current crosses the Mendeleev Ridge (likely in the north where the ridge is least distinct) and loops around the Chukchi Rise [Shimada et al., 2004; Woodgate et al., 2007]. Yet, data also suggest other pathways – e.g., along the east side of the Chukchi Rise [Woodgate et al., 2007], or a shortcut at ~ 76N south of the Chukchi Rise [McLaughlin et al., 2004]. Curiously, this second pathway is absent in 2002, suggesting (hitherto unexpected) variability in AW boundary current pathways. Another enigma is the unexpected delay for the FSBW warming to traverse the Northwind Ridge south to the Chukchi Slope [Shimada et al., 2004]. To resolve these pathway issues, we will first extend the CBL2002 analysis of T-S, zigzags and tracers [Woodgate et al., 2007] to include other 2002 data (JWACS, NOAA, Mirai) to study pathways along the Northwind Ridge and Chukchi Rise. We will also compute geostrophic velocities, and reference them where possible to current meters, buoy data, or educated estimates of levels of known motion. Having mapped structures in 2002, we will extend the analysis to other years, to ascertain how pathways vary interannually. Data coverage in this region in 2004 (Mirai, JWACS, NOAA) is similar to 2002, and SCICEX data coverage is particularly relevant between 1995 and 2000 (Figure 6). F  igure 6: Example of Mendeleev Ridge and Chukchi Borderland (CTD/XCTD) station coverage (data sources and exclusions as per Figure 5) colored by year – black=pre-1991; red=1991-1995; magenta=1996-1997; blue=1998-2002; cyan=2003; green=2004-2005; yellow=2006-2007. Topography schematic, contoured at 500m. Note exact repeat lines (e.g., the SCICEX repeats at ~ 150W) are hidden by this representation.
Properties: These data sets will also be used to determine the isobath range of the boundary current, and combined with mooring and buoy data will investigate other flow properties, such as along/across slope, variability, presence of eddies, and vertical structure. By considering the speed of advection of the FSBW warming, and the volume of new FSBW and BSBW found on each section, we will rank the importance of the various pathways, considering also interannual variability. Where possible, we will also make estimates of volume transports. A line of 3 CBL moorings west of the Chukchi Rise [Woodgate et al., 2003] show the eastward-flowing boundary current, but also an intriguing inshore counter flow, which we will compare to tracer measurements and T-S and geostrophic calculations from section data in other years. Processes of exchange: Again, we aim to estimate losses from the boundary current due to double diffusive processes, eddy shedding, and shelf-interactions. The repeat SCICEX sections off the north end of the Northwind Ridge [e.g., Figure 6 above and Figure 2 of Woodgate et al., 2007] show the T-maximum and the zigzags further north away from the slope every year. Are these features being advected parallel to the boundary current or are they caused by intrusions propagating perpendicular to the boundary current as suggested by theory [McDougall, 1985]? The key to distinguishing these processes is the properties of the non-boundary current part of the zigzag – if the zigzags are locally formed, then the waters intruding into the boundary current are local; if the zigzags are advected with/parallel to the boundary current, all parts of the zigzag are of distant origin. We will use T-S and tracer (especially dissolved oxygen) data to distinguish between these possibilities. If (as we suspect), the results prove intrusions moving perpendicular to the boundary current, we will use the interannual change in extent to assess spreading speed away from the boundary current, and (with depth data) quantify the volume lost from the boundary current, per unit length (see also below). We will also seek eddies in the offshore data in this region (and in the Canadian Basin), and, using tracer data, make estimates of the volume of water shed by eddies from the boundary current. Finally, we will identify T-S characteristics of shelf-slope interactions to assess the ubiquity of upwelling and mixing or polynya ventilation in this region. In 2002 [Woodgate et al., 2005a], upwelling and mixing dominated the upper AW layers in the CBL region. We will ascertain if this is true in other years. Northwind Ridge enigma: If the volume of boundary current water lost (either by intrusions or eddies) north of the Chukchi Rise is large, this may explain why the FSBW T-maximum is so slow to propagate along the Northwind Ridge – i.e., the warming signal is eroded before it reaches the ridge. Alternatively, the boundary current may have taken a different dominant route (via the east side of the Chukchi Rise) – a possibility tested above. A third option is that the Northwind Ridge current is variable, and if coverage is sufficient, we will test this with drifting buoy data. 2.3c The Makarov Basin and the Lincoln Sea Our final, most explorative, regional focus is the Makarov Basin. Old, short-term (days) current meter data from the Siberian end suggest a topography following current [Newton and Coachman, 1974], and stronger flows over topography are inferred from bottom nepheloid layers [Hunkins et al., 1969]. There is a large collection of recent, uncollated data from this region (e.g., Figure 7), including at least 7 years of SCICEX crossings (1993-2000), 3 major hydrographic cruises (Oden, AOS, Healy), aircraft stations (2000-present), and drifting buoy data. Hydrography and tracers suggest the basin is slowly ventilated from the south, with possibly cyclonic flow around the basin [Swift et al., 1997; Smethie et al., 2000; Kikuchi et al., 2005]. Yet, to date, remarkably little has been published and important facts lie unreported in these data – e.g., the SCICEX repeats show the FSBW warming entered the mid Makarov Basin between 1995 and 1998 (Figure 7, unpublished). A detailed analysis will very likely yield pathway and spreading rate information. 
Figure 7: (Left) Sample of Makarov (CTD/XCTD) station coverage (data sources and exclusions as per Figure 5) colored by year – red=1991-1995; magenta=1996-1997; blue=1998-2002; cyan=2003; green=2004-2005; yellow=2006-2007. Topography schematic, contoured at 500m. Note exact repeat lines are hidden by this representation. Black dots mark moorings at the Siberian end of ridge. Small black dots are historic, short-term bottom measurements [Newton and Coachman, 1974]. T-S diagram (middle) and T-profiles with depth (right) for the SCICEX repeat-XCTD (black=1993, east of later stations; blue=1995; green=1998; yellow=1999, red=2000) at ~ 85N on the Mendeleev Ridge northern flank (black oval on left panel). The FSBW warming arrives at this section between 1995 and 1998. Poor salinity data masks structure in T-S space, however the zigzags are evident in the T-profiles. Pathways: Zigzag analysis particularly exciting in this region, since this new technique extracts more meaning from the older datasets, can compensate for poor S data, and can be used to place the sparser modern data of airborne surveys (e.g., NPEO and SW) into proper context (e.g., are they measuring the boundary current or the interior?). As in the other regions, we will map FSBW and BSBW properties using T-S and zigzags, and available tracer data. We will use the remarkably good SCICEX coverage to track the pathways of the FSBW warming as it enters the Makarov, study the isobath range of the boundary current, and at least bound spreading rates. We will compare our results to hypothesized pathways (e.g., northward flow along the Mendeleev Ridge, and leakage through gaps in the Lomonosov Ridge) and the older, short-term current measurements that exist. Properties and processes: Techniques explained and developed in the other regional analysis will be used here also. The SCICEX data coverage is sufficient to elucidate if the AWs are concentrated in a topography-following boundary current, as elsewhere. We will compute geostrophic shear from quality hydrographic data. We will catalog any eddies found in the many basin crossings, and compare eddy occurrence per unit track length with other parts of the western Arctic, to estimate relative eddy abundance in the different basins. 2.4 Pan-basin issues and overarching aims The final, overarching goal of our work is to bring together the regional results into a pan-Basin view of AWs in the western Arctic. Central themes are (a) defining differences and similarities between the AW flow in different regions, including basic flow structure (speed, transport, isobath range, vertical structure, variability); and (b) quantifying processes of boundary current to interior and boundary current to shelf exchange, including their relative importance. A simple volume budget is informative. The AW input to the western Arctic estimated from moorings is ~ 2 Sv [Woodgate et al., 2001]. A Makaov Basin slope mooring (same reference) measured 2-3, ~ 1000 m deep eddies in 1 year. Assuming a 10 km radius (based on the Rossby radius), spawning 3 eddies a year is a loss from the boundary current ~ 0.03 Sv. This suggests that (in volume) eddy loss from the boundary current is small, but this estimate must be updated in light of results of eddy abundance in the western Arctic. In contrast, a simple estimate suggests double diffusive transfer is sizeable. Assuming a zigzag layer thickness of 400 m (and thus ~ 200 m outgoing intrusions), a 2 mm/s lateral spreading [Walsh and Carmack, 2003] is equivalent to 0.04 Sv per 100 km of boundary current. The boundary current traverses 1000s of km (Lomonosov Ridge to the Mendeleev Ridge is ~ 1200 km; Mendeleev Ridge to the south of the Northwind ridge is ~ 600 km by a shallow slope route and ~ 1400 km via north of the Chukchi Rise). Thus, the double diffusive exchange over these distances (say 2000 km) is ~ 0.8 Sv, a sizeable portion of the estimated boundary current, and perhaps an order of magnitude larger than eddy exchange. Our analysis of eddies, double diffusive spreading rates, and the ubiquity of zigzags will test if such simple estimates correctly represent observed boundary current-interior exchange. In this concluding phase we will work closely with modelers and theoreticians to define key features of the AW circulation which are essential for model and theory verification. Our results will provide input to AON planning, for example suggesting locations and depth ranges for moorings or CTD surveys, or indicating important processes requiring further study. As this work concludes, we will reach out to European colleagues working on the boundary current in the Eurasian Basin, for a pan-arctic overview of AWs in the Arctic. 2.5 Data products and archiving This project requires the assembly of a large number of various arctic data sets. In recent years, the number of data sets has grown significantly. Although the NODC (National Oceanographic Data Center) World Ocean Database 2005 holds archives of many arctic data, there are 1-2 year delays between data being submitted and being publicly accessible. Similarly, the data collection at the Arctic System Science Data Coordination Center (ADCC) is also incomplete. Moreover, these data centers do not provide easy visualization of data – it is usually necessary to extract the data before a researcher can test its relevance to their work. Thus, we will make part of our project, the building of a publicly accessible web-catalogue of international hydrographic data sets from the Canadian Basin in the last two decades. Primarily the site will be a listing, by year, of all data sets collected, including a brief description of the data and a link to a data source. If the data are public, we will also include a link to the data and some basic schematics (e.g., maps, T-S sections, T-S plots) to indicate to potential users the value of the data set. Collation of data for the Beaufort Gyre region has been done by the Beaufort Gyre Exploration Project. We will extend the coverage of that collection to the entire Canadian Basin, including the Chukchi Borderland, and the Makarov Basin. We will also include mooring data information and plots. We will attempt to cover all data sets (except the large Russian database, which is not generally publicly available) in the last two decades up to 2007, the start of the latest International Polar Year (IPY). We will not include IPY data, since they are to be catalogued extensively elsewhere. We will check our data holdings with NODC and archive any data we rescue which are not in their collections. We will encourage (and, if requested, aid) other investigators who are kind enough to share unpublished data to submit their data to NODC. This collation is intended as a tool for our research and for the work of other arctic investigators, and will complement (not duplicate) the permanent data archives. By providing basic data plots, it will simplify access to real data for those unfamiliar with arctic data and/or observational oceanographic data visualization techniques. It also has a secondary (short-term) use, as it will provide a publicly available listing of arctic datasets submitted to national archives but not yet released. In accordance with NSF policy, we will archive our collection of data listings at ADCC (or the NSF-chosen arctic data archive) in a timely manner, including a preliminary version early in the research and a complete version at the end of the research. 2.6 Outreach There are four outreach components to our project, aimed at the arctic (and sub-arctic) research community; the student community; local schools and colleges; and the general public. Our contributions to the research community are (a) to provide an observationally-based description of the western Arctic AW circulation over the last two decades, and (b) to create a “one-stop” website of hydrographic data from the Canadian Basin (as described above). The collation of data will allow easy comparison to model and theory results. We will also provide a quantified description of the flow structure (e.g., boundary current width, vertical structure, etc.) to test and suggest theoretical approaches. Thus, our results will advance the research of arctic observationalists, modelers, and theoreticians working on an understanding the AW circulation. During the project, we will collaborate closely with two leaders in arctic circulation theory, Greg Holloway and Ole Anders Nost. (Both have independent funding for this work.) Furthermore, our analysis will elucidate gaps in our knowledge, and thus guide planning for the evolving Arctic Observing Network (AON). Without the proposed synthesis, initial years of AON will proceed without guidance from the large archives of recent arctic data. Our work contributes to goals of SEARCH (Study of Environmental Arctic CHange) and ISAC (International Study on Arctic Change). Our project includes funds for one graduate student, to be supervised jointly by Woodgate and Rhines of the University of Washington (UW), the latter at no cost to this proposal. Although primarily focusing on analysis of observational data, the student will also gain experience of theoretical and modeling approaches to an oceanographic problem, and be trained to bridge the traditional gaps between observationalists, modelers, and theoreticians. (Although now focused on observations, Woodgate did her thesis work on data assimilation, combining modeling and theoretical approaches.) Project results will be brought to other UW students, via an interdisciplinary arctic course taught jointly by Woodgate and Deming at UW’s School of Oceanography, and via interactions with UW’s Program on Climate Change, a pan-departmental interdisciplinary teaching and research program of which Woodgate is a Board member. The project will also support the PI and the graduate student in outreach events at local schools and colleges, bringing an understanding of the Arctic, oceanography, and climate change to Seattle K-12 schools and Seattle’s Shoreline Community College. When in Alaska for other field work projects, Woodgate will extend this K-12 outreach to local arctic communities. Finally, in addition to a publicly accessible website, we will involve the general public in our research via a focused arctic circulation “Spinning around the Arctic” exhibit at the Polar Science Weekend, a collaborative venture with the Pacific Science Center, Seattle’s major science museum. This exhibit will include examples of conservation of angular momentum and vorticity (e.g., a volunteer on a spinning chair, and experiments with rotating objects on turntables) to illustrate the possible large-scale driving of arctic circulation. 2.7 Task distribution and time line Year 1: - collate data sets; set up website; submit meta data to data archive; analyze and publish (with collaborators) results from the Chukchi/Beaufort slopes and Beaufort Sea; provide input to AON planning and IPY analysis. Year 2:- analyze and publish (with collaborators) Chukchi Borderland and Northwind Ridge results; compare observational results with theoretical and modeling predictions; provide input to AON planning and IPY analysis. Year 3: - analyze and publish Makarov Basin results; archive rescued data; publish pan-basin synthesis of AW in the Canadian Basin; define key regions for future Canadian Basin measurements, based on combined observations, theoretical, and modeling results. All Years:- maintain close dialog with theoreticians/modelers; outreach in Seattle schools and community colleges, and at the Polar Science Weekend at Seattle’s Pacific Science Center. Woodgate is responsible for project coordination. She will take the lead on data collation and analysis, the website, interactions with collaborators (Carmack, McLaughlin, Shimada, Holloway, Nost), publication of results, and primary supervision of the graduate student. Graduate student, while completing course work in the first years, will assist in data collation and analysis, and play a key role in the Polar Science Weekend outreach. In years 2 and 3, s/he will take the lead on a subproject that suits their growing research interests, be they strongly observational (e.g., analysis of Makarov Basin results) or more interdisciplinary (e.g., comparison of observations with predictions from modeling or theory). Programmer (Runciman) will assist with all computational aspects, data collation and visualization, and the website. She will also take the lead in archiving rescued data. 2.8. Timeliness and transformative potential In recent years, there has been little active research on the Atlantic Waters of the western Arctic, despite their pan-arctic impacts and global connections, and an order of magnitude increase in available data. Our proposed work is very timely, since this lack of knowledge of the circulation and exchanges of AW is now hindering advances in related arctic and global theoretical and modeling studies and leaves us poorly situated to implement an efficient arctic observing system, or predict future scenarios in the Arctic Ocean. The work has transformative potential, since it bridges the traditional gaps between observationalists, modelers and theoreticians, to build an observationally-based, but theoretically underpinned understanding of a key part of the Arctic climate system. 3. PRIOR WORK: OPP-0117480: “Collaborative Research: The Influence of the Mendeleev Ridge and Chukchi Borderland on the Large-scale Circulation of the Arctic Ocean”; $431K; PI: Woodgate, Co-PIs: Aagaard, Smethie, Swift, Falkner; 11/2001 – 12/2004. Science: This project, based on 2002 CBL field work [Woodgate et al., 2003], studies the effects of the complex topography of the Mendeleev Ridge and Chukchi Borderland on the large-scale circulation of the Arctic. This region is an “Arctic Crossroads” where the warmer, saltier, cyclonically flowing, topographically-steered Atlantic-origin waters [Woodgate et al., 2001] encounter the colder, fresher, nutrient-rich Pacific waters exiting the Chukchi Sea [Woodgate et al., 2005a; Woodgate et al., 2005b]. The fate of these waters is important for local and regional ocean conditions, ice-cover and ecosystems, and global ocean climate. Project results elucidate processes of shelf-basin exchange. We find that a major part of arctic halocline ventilation is due to Atlantic Water upwelling and diapycnal mixing over the northern Chukchi Shelf/Slope [Woodgate et al., 2005a]. Using oxygen structure, we trace shelf waters across the Arctic Ocean [Falkner et al., 2005]. By using information hidden in thermohaline intrusions, our work also describes the boundary current pathways through the Mendeleev Ridge and Chukchi Borderland, and documents water mass changes in the Atlantic Water layers [Woodgate et al., 2007]. Education and Outreach: The research has resulted in one MSc thesis [Balster, 2003] and an undergraduate research project [Grimes, 2002]. Through classroom visits, and a teacher’s cruise diary (psc.apl.washington.edu/CBLteacher.html), over 3000 individuals, including school-classes across the country, experienced both the Arctic and leading edge oceanographic research. Woodgate – Atlantic Waters in the Western Arctic Project Description : Directory: rebecca rebecca -> Education 2005 Masters of Fine Art, California Institute of the Arts, Valencia, Los Angeles, usa. 2002 Honors year, Bachelor of Fine Arts, The Victorian College of the Arts, Melbourne, aus. 2001 Bachelor of Fine Arts, Photography Major, V rebecca -> Irina Khasin, Legal Counsel and Secretary rebecca -> Education Ph. D. American Studies, University of Maryland, College Park, 2010 Fields: humor studies, performance studies, visual/popular culture, women’s history, cultural studies and studies in race/ethnicity, gender, disability rebecca -> The Unbelievable Truth Download 2.02 Mb. Share with your friends:
|