Nares Strait Research Articles

Submarine glacial landform distribution in the central Arctic Ocean shelf–slope–basin system

The central Arctic Ocean, including its surrounding seas, extends over an area of c. 9.5×106 km2 of which c. 53% comprises shallow continental shelves (Jakobsson 2002) (Fig. 1a). The surface of this nearly land-locked polar ocean is at present dominated by a perennial sea-ice cover with a maximum extent every year in late February to March and a minimum in early to mid-September (Fig. 1a) (Serreze et al. 2007). Outlet glaciers producing icebergs that drift in the central Arctic Ocean exist on northern Greenland, Ellesmere Island and on islands in the Barents and Kara seas (Diemand 2001) (Fig. 1a). Ice shelves, although substantially smaller than those found in Antarctica, presently exist in some of Greenland's fjords (Rignot & Kanagaratnam 2006), on Severnaya Zemlya (Williams & Dowdeswell 2001) and along the northern coast of Ellesmere Island (Jeffries 1992; Williams & Ferrigno 2012). Existing ice shelves around the Arctic Ocean are primarily formed through accretion of multiyear sea ice and gain their mass from snowfall and/or basal freezing. Fig. 1. ( a ) Bathymetric map of the Arctic Ocean and study areas (red boxes, map from IBCAO v. 3.0). Purple line is mean minimum sea-ice extent (September). Pink line is mean maximum sea-ice extent (March). AGT, Amundsen Gulf Trough; AP, Arlis Plateau; BS, Bering Strait; CP, Chukchi Plateau; CR, Chukchi Rise; FS, Fram Strait; HC, Herald Canyon; LR, Lomonosov Ridge; McT, M'Clure Trough; MJR, Morris Jesup Rise; MT, Mackenzie Trough; MR, Mendeleev Ridge; NS, Nares Strait; StT, St Anna Trough; YP, Yermak Plateau. ( b ) Ice-sheet extent during Last Glacial Maximum (LGM) (from Ehlers & Gibbard 2004; Svendsen et al. 2004; England et al. 2009). LGM topography is from ICE-5G (Peltier 2004). ( c ) Western section of the Canadian Arctic Archipelago with outlines of the main CSTs (black line) and …

Volume and Freshwater Flux Observations from Nares Strait to the West of Greenland at Daily Time Scales from 2003 to 2009

AbstractTime series observations of velocity, salinity, pressure, and ice draft provide estimates of advective fluxes in Nares Strait from 2003 to 2009 at daily to interannual time scales. Velocity and salinity are integrated across the 36-km-wide and 350-m-deep channel for two distinct multiyear periods of sea ice cover. These observations indicate multiyear mean fluxes that range from 0.71 ± 0.09 to 1.03 ± 0.11 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1 = 31 536 km3 yr−1) for volume and from 32 ± 5.7 to 54 ± 9.3 mSv (1 mSv ≡ 103 m3 s−1) for oceanic freshwater relative to a salinity of 34.8 for the first (2003–06) and second (2007–09) periods, respectively. Advection of ice adds another 8 ± 2 mSv or 260 ± 70 km3 yr−1 to the freshwater export. Flux values are larger when the sea ice is mobile all year. About 75% of the oceanic volume and freshwater flux variability is correlated at daily to interannual time scales. Flux variability peaks at a 20-day time scale and correlates strongly with along-channel pressure gradients (r2 = 0.68). The along-channel pressure gradient peaks in early spring when the sea ice is often motionless with higher sea level in the Arctic that drives the generally southward ocean circulation. Local winds contribute only when the sea ice is mobile, when they explain 60% of its variance (r2 = 0.60). Observed annual to interannual change in the duration of motionless sea ice conditions impacts ocean stratification and freshwater flux, while seasonal variations are small.

Modeled ocean circulation in Nares Strait and its dependence on landfast‐ice cover

AbstractTwo simplified ocean simulations are used to study circulation and transport within Nares Strait. The simulations are similar, except that one included a coupled sea ice model that effectively established a landfast ice cover throughout the simulation year. Comparison between the ocean‐only and ocean‐ice simulations reveals a systematic change in the current structure, reminiscent of the seasonal shift under mobile and landfast ice previously observed in Nares Strait. A surface‐intensified jet, which carries low‐salinity water along the strait's centerline, develops within the ocean‐only simulation. The current structure under landfast ice is characterized by a subsurface jet located along the western side with low‐salinity surface water distributed along the eastern side of the strait. Intermediate salinity water is offset to the west in the ice‐ocean simulation relative to the ocean‐only simulation, while high‐salinity water (>34.8) is constrained to recirculations that are located north and south of a sill in Kane Basin. The simulations, combined with an idealized, semianalytical model, suggest that the structural shift is caused by the surface Ekman layer beneath the landfast ice and the associated eastward advection of near‐surface low‐salinity water and westward movement of the jet. Temporal variability in the ocean‐ice simulation is dominated by the remote response to the time‐dependent northern boundary conditions. In contrast, the ocean‐only simulation favors an instability and additionally responds to local surface wind forcing, which enhances the variability within the strait above that imposed at the boundaries.

Initiation of the last ice age in Canada by extreme precipitation resulting from a cascade of oceanic salinity increases

Numerical modeling has failed to confirm the classical Milankovitch hypothesis of initiation of the last ice age by Northern Hemisphere high latitude cooling due to decreasing summer insolation caused by orbital effects. The modeling failed to confirm ice sheet growth even with a widespread layer of glacial ice as an initial condition to embody positive feedback. The failure probably occurred because the initial conditions of the calculation did not include the actual effects of an altered climate in northeastern Canada that brought a sharp cooling to Europe and extreme amounts of precipitation to cloud-covered lands west of Greenland. In the conceptual model proposed here, diminishing orbital summer insolation in northern Africa is causally linked to this regional climate change by a cascade of oceanic salinity changes. The summer cooling in northern Africa weakened the monsoons, reduced the Nile River flow, and increased Mediterranean salinity and outflow at Gibraltar. The salt in the outflow contributes substantially to the salinities of the North Atlantic Drift and the Greenland Sea, to the formation rate of North Atlantic Deep Water (NADW) there, and to the northward flow of the Spitsbergen-Atlantic Current (SAC) that replaces the sinking NADW. When the increasing salt in the Mediterranean outflow made the SAC replacement flow sufficiently strong, the flow penetrated into the polar ocean along the north coast of Greenland. Denser and more saline Atlantic water then replaced the polar water flowing southward into Baffin Bay through the Nares Strait and Lancaster Sound, thus eliminating the stratification in the bay that enables freezing of winter sea ice. Without the southward flow of sea ice out of Baffin Bay, the Labrador Sea became much warmer. The warmer seas west of Greenland then triggered a persistent cyclonic circulation that caused large amounts of precipitation in eastern Canada and a much colder northern Europe. The resulting Canadian erosion yielded a 500yr-long deep-sea sediment record of the ice-free condition. Heavy snowfall started new ice sheet growth on Baffin Island, northern Quebec, Labrador, western Greenland, and the Barents Sea, causing world sea level to fall at a rate of 0.5cmyr-1. The modern increasing salinity of the Mediterranean Sea and extension of SAC flow into the polar ocean are now following the cascade steps toward an ice-free Baffin Bay and possible near term regional climate deterioration.

Multiyear ice replenishment in the Canadian Arctic Archipelago: 1997–2013

AbstractIn the Canadian Arctic Archipelago (CAA), multiyear ice (MYI) replenishment from first‐year ice aging (CAAMYI‐Oct‐1) and Arctic Ocean MYI exchange (CAAMYI‐exchange) contribute to the CAA's relatively heavy sea ice conditions at the end of the summer melt season. We estimate these components using RADARSAT and the Canadian Ice Service Digital Archive and explore processes responsible for interannual variability from 1997 to 2013. CAAMYI‐Oct‐1 (52 ± 36 × 103 km2) provides a larger contribution than CAAMYI‐exchange (13 ± 11 × 103 km2). CAAMYI‐Oct‐1 represents ∼10% of the amount that occurs in the Arctic Ocean. CAAMYI‐exchange represents ∼50% of Nares Strait MYI export to Baffin Bay and ∼12% of Fram Strait MYI export to the Greenland Sea. CAAMYI‐Oct‐1 exhibits dependence on warmer (cooler) summers that increase (decrease) melt evident from strong relationships to surface air temperature (SAT), albedo and total absorbed solar radiation (Qtotal). CAAMYI‐exchange is influenced by summer sea level pressure (SLP) anomalies over the Beaufort Sea and Canadian Basin which shifts the primary source of CAAMYI‐exchange between less obstructed M'Clure Strait (low SLP anomalies) and the more obstructed Queen Elizabeth Islands (high SLP anomalies). Over the 17‐record, appreciable replenishment occurred for most years from 1997 to 2004, reduced replenishment from 2005 to 2012, and large replenishment in 2013. The reduced replenishment period was associated with positive SAT, negative albedo, and positive Qtotal anomalies that facilitated more melt and less CAAMYI‐Oct‐1, together with high SLP anomalies that facilitated less CAAMYI‐exchange. Large replenishment in 2013 was primarily from CAAMYI‐Oct‐1 attributed to strongly negative SAT and Qtotal anomalies and strongly positive albedo that impeded melt.

Abundance of Atlantic walrus in Western Nares Strait, Baffin Bay Stock, during summer

Atlantic walruses (Odobenus rosmarus rosmarus) belonging to the Baffin Bay subpopulation occur year round in the North Water polynya (NOW) between NW Greenland and eastern Ellesmere Island (Canada). They are hunted for subsistence purposes by residents of the Qaanaaq area (NW Greenland) bordering the NOW to the east and by Canadian Inuit at the entrance to Jones Sound in Nunavut. During the open-water period NW Greenland is virtually devoid of walruses which concentrate along eastern and southern Ellesmere Island at this time of the year. To determine the abundance of walruses in the NOW area, aerial surveys were conducted in August of 1999, 2008, and 2009. In July 2009, nine satellite-linked transmitters were deployed in nearby Kane Basin. Surveys on 9 and 20 August 2009 along eastern Ellesmere Island were the most extensive and were augmented with concomitant data on haul-out and at water surface activity from three (1 F, 2 M) of the nine tags that were still functioning. We therefore focus on the 2009 surveys. Walruses were observed on the ice and in water primarily in Buchanan Bay and Princess Marie Bay where the remaining functional tags were located. The Minimum Counted population (MCP) was 571 on 20 August. Adjusting the MCP of walruses on ice for those not hauled out, the estimate of abundance of walruses in the Baffin Bay stock was 1,251(CV=1.00, 95% CI = 1,226) when adjusted by the proportion of tags ‘dry’ at the time of the survey and 1,249 (CV=1.12, 95% CI = 1,370) when adjusted by the average time tags were dry. The surveys did not cover all potential walrus summering habitat along eastern Ellesmere Island and are negatively biased to an unknown degree.

Baffin Island and West Greenland Current Systems in northern Baffin Bay

Temperature, salinity, and direct velocity observations from northern Baffin Bay are presented from a summer 2003 survey. The data reveal interactions between fresh and cold Arctic waters advected southward along Baffin Island and salty and warm Atlantic waters advected northward along western Greenland. Geostrophic currents estimated from hydrography are compared to measured ocean currents above 600m depth. The Baffin Island Current is well constrained by the geostrophic thermal wind relation, but the West Greenland Current is not. Furthermore, both currents are better described as current systems that contain multiple velocity cores and eddies. We describe a surface-intensified Baffin Island Current seaward of the continental slope off Canada and a bottom-intensified West Greenland Current over the continental slope off Greenland. Acoustic Doppler current profiler observations suggest that the West Greenland Current System advected about 3.8±0.27Sv (Sv=106m3s−1) towards the north-west at this time. The most prominent features were a surface intensified coastal current advecting 0.5Sv and a bottom intensified slope current advecting about 2.5Sv in the same direction. Most of this north-westward circulation turned southward in the Baffin Island Current System. The Baffin Island system was transporting 5.1±0.24Sv to the south-east at the time that includes additional contributions from Nares Strait to the north (1.0±0.2Sv) and Lancaster Sound to the east (1.0±0.2Sv). Net freshwater fluxes were 72 and 187mSv for the West Greenland and Baffin Island Currents, respectively. Empirical uncertainty arises from unknown temporal variations at weekly time scales and pertubations introduced by unresolved eddies. Eddies with 10km horizontal and 400m vertical scales were common and recirculated up to 1Sv. Our 2003 observations represent conditions when the North-Atlantic Oscillation index (NAO) was close to zero. Analysis of historical hydrographic data averaged along isobaths during NAO-positive years reveals a baroclinic circulation in Baffin Bay more intense than 2003 with stronger southward flow of fresher Arctic waters along Baffin Island and stronger northward inflow of saltier Atlantic waters along Greenland. During negative NAO years this cyclonic circulation weakens as evidenced by a 1979 synoptic survey of the hydrography along Baffin Island.

Model simulated volume fluxes through the Canadian Arctic Archipelago and Davis Strait: Linking monthly variations to forcing in different seasons

The solution of a 10 year simulation of the Arctic Ocean, produced using a 6 km resolution coupled ocean and sea-ice model, is analyzed to understand the variability, control, and forcing mechanisms of the volume fluxes through the Canadian Arctic Archipelago (CAA) and Davis Strait (DS). The analysis focuses on variability at monthly time scales. Analysis confirms the “control” of volume fluxes through the CAA, proposed in previous studies, by (1) variations of sea surface height (SSH) in the “upstream” regions and the relationship of this control to alongshore wind in the Beaufort Sea and (2) by SSH in the “downstream” region in Baffin Bay that may be related to wind stress in Baffin Bay and the northern Labrador Sea. The effectiveness of these control and forcing mechanisms vary for fluxes through different sections and for different seasons. Variation of the southward flux through DS is directly influenced by fluxes through Nares Strait (NS) and Barrow Strait (BS) in summer, fall, and winter. In spring, variations of the southward and northward fluxes through DS are closely related to each other and correspond to changes in the SSH along pathways of the Irminger Current, and the East and West Greenland Currents.

Interannual changes of the floating ice shelf of Petermann Gletscher, North Greenland, from 2000 to 2012

AbstractPetermann Gletscher, northwest Greenland, drains 4% of the Greenland ice sheet into Nares Strait. Its floating ice shelf retreated from 81 to 48 km in length during two large calving events in 2010 and 2012. We document changes in the three-dimensional ice-shelf structure from 2000 to 2012, using repeated tracks of airborne laser altimetry and ice radio-echo sounding, ICESat laser altimetry and MODIS visible imagery. The recent ice-shelf velocity, measured by tracking surface features between flights in 2010 and 2011, is ~1.25 km a−1, ~15–30% faster than estimates made before 2010. The steady- state along-flow ice divergence represents 6.3 Gta−1mass loss through basal melting (~5Gta−1) and surface melting and sublimation (~1.0Gta−1). Airborne laser altimeter data reveal thinning, both along a thin central channel and on the thicker ambient ice shelf. From 2007 to 2010 the ice shelf thinned by ~5 m a−1, which represents a non-steady mass loss of ~4.1 Gta−1. We suggest that thinning in the basal channels structurally weakened the ice shelf and may have played a role in the recent calving events.

Improvements in LICOM2. Part II: Arctic Circulation

Abstract A known issue of the National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics Climate Ocean Model, version 2 (LICOM2, the standard version) is the use of an artificial island in the Arctic Ocean. The computational instability in the polar region seriously influences the model performance in terms of the Arctic circulation. The above-mentioned instability was originally attributed to the converging zonal grids in the polar region. However, this study finds that better computational stability could be achieved in an improved version of LICOM2 (i.e., LICOM2_imp) after four improvements on implementations of the vertical mixing, mesoscale eddy parameterization, and bottom drag schemes. LICOM2_imp is then able to reduce the aforesaid artificial island to a point (i.e., the North Pole). Two experiments of 650-yr integration by LICOM2_imp are carried out using different bathymetries: Exp IMPV0 with the artificial island (88°–90°N) and IMPV1 with only the single pole. The focus of this paper is on the Arctic circulation. Exp IMPV1 gives a more reasonable distribution of salinity and temperature in the Arctic Ocean, a more accurate location of the center of the Beaufort Gyre, and a better net volume flux of the transpolar drift. With more realistic bathymetry in the Arctic Ocean, the biases of net volume fluxes across the Fram Strait, Barents Sea Opening, and Barents Sea Exit are reduced from 1.71 to 1.56, from 0.23 to 0.10, and from 0.71 to 0.45 Sv (1 Sv ≡ 106 m3 s−1), respectively, closer to the observations. The large biases of the net volume fluxes at the Fram Strait in both experiments may be attributed to the closed Nares Strait and other straits/channels in the Canadian Arctic Archipelago.

Comment on “A new model for the Paleogene motion of Greenland relative to North America: Plate reconstructions of the Davis Strait and Nares Strait regions between Canada and Greenland” by G. N. Oakey and J. A. Chalmers

Comment on “A new model for the Paleogene motion of Greenland relative to North America: Plate reconstructions of the Davis Strait and Nares Strait regions between Canada and Greenland” by G. N. Oakey and J. A. Chalmers

On the waters upstream of Nares Strait, Arctic Ocean, from 1991 to 2012

The Lincoln Sea is a bifurcation point, where waters from the Canadian and Eurasian Basins flow to Nares or Fram Strait. Mechanisms that control which waters are found in the Lincoln Sea, and on its continental shelves, are unknown. Using conductivity–temperature–depth (CTD; from hydrographic and ice-tethered profiler surveys), nutrient, and mooring data with the DRAKKAR global 3-D coupled ocean/sea-ice model, the Lincoln Sea was examined from 1991 to 2012. Although both Pacific and Atlantic waters were observed on the North Ellesmere and North Greenland shelves, Atlantic water was shallower on the North Greenland shelf. Thus, deeper than 125m, water was warmer and saltier on the North Greenland shelf than the North Ellesmere shelf. Three different water types were identified on the North Ellesmere shelf – waters from the Canadian Basin were observed 1992, 1993, 1996, 2005, and 2012, waters from both the Canadian and Eurasian Basins were observed in 2003, 2004, and 2008, and waters with no temperature minima or maxima below the surface mixed layer were observed in 1991, 2006, 2009, and 2010. Mixing with vertical advection speeds of 1×10−4ms−1 were observed on the continental slope and this mixing could cause the disappearance of the temperature maxima. Model results suggest that currents on the North Ellesmere shelf were weak (less than 10cms−1), baroclinic, and directed away from Nares Strait while currents on the North Greenland shelf were stronger (less than 15cms−1), and primarily directed towards Nares Strait. CTD, mooring, and model results suggest that the water advected to Nares Strait is primarily from the North Greenland shelf while water on the North Ellesmere shelf is advected westward.

The rotations opening the Central and Northern Atlantic Ocean: compilation, drift lines, and flow lines (Int J Earth Sci 102:1357–1376)

Strait and marked the Wegener Fault. Figure 1b depicts the present-day geography and geology of the region modified from Dawes (2009, Fig. 9). The mismatch between Ellesmere Island and Greenland in Fig. 1a is immediately apparent from the disruption of the two sedimentary basins—the Mesoproterozoic Thule and Paleozoic Franklinian—that straddle nares Strait. The component of the Thule Basin on Greenland is displaced from that on Ellesmere Island. The regional architecture of the Franklinian Basin depicted in Fig. 1b by cambrian to Devonian markers in Ellesmere Island and Greenland is destroyed and the cambro-Silurian, folded, deep-water trough of the Franklinian Basin on Greenland strikes into Paleoproterozoic gneiss on Ellesmere Island. Other misfits on a more detailed scale are listed by Dawes (2009). In addition, closure of the major seaways flanking Devon Island (Lancaster and Jones Sounds) likewise results in gross mismatches within canadian geology. Similar problems arising from the undoing of harmonious geology mar Greiner and neugebauer’s reconstructions at 84 and 52.65 Ma. Saalmann et al. (2005) described a Paleogene, nEtrending, strike-slip fault zone and later SE-directed thrusting on land in a 100-km-long stretch of the nE Ellesmere Island coastline. They considered this deformation to be a manifestation of the Wegener Transform Fault and plate boundary but admitted that the fault could not be traced farther south through southern nares Strait into Baffin Bay. Greiner and neugebauer have used Saalmann et al.’s findings to support their case for convergence of Greenland and Ellesmere Island and large-scale displacement along the Wegener Fault but fail to acknowledge that these Paleogene tectonic features are of limited regional significance and that, in any event, the amount of strike slip recorded on land is insufficient to account for the separation of Greenland from north America by spreading in Baffin Bay. Greiner and neugebauer (2013) have modeled the opening of the central and northern Atlantic Ocean using a computer program that generates paleogeographic reconstructions based on Euler rotational data, which in turn are derived from magnetic anomalies flanking oceanic spreading ridges. Here, we confine ourselves to a critique of Greiner and neugebauer’s results for the nares Strait—northern Baffin Bay region bordered by Greenland and the eastern canadian High Arctic. Reconstructions at or before 175, 84, and 52.65 Ma are shown in Greiner and neugebauer’s Figures 5, 6, 9, and 10. All these are strictly paleogeographic representations; none shows any surface geological feature. Greiner and neugebauer a priori consider Greenland to be an independent tectonic plate separated from Ellesmere Island—part of the north American plate—by a transform fault, the Wegener Fault, running through nares Strait. They accept the Wegener Fault as a proven structure and overlook abundant evidence that it is hypothetical (Oakey and Damaske 2006; Harrison 2006; Dawes 2009; Hansen et al. 2011; Rasmussen and Dawes 2011). They cite only one reference to geology relevant to their reconstructions, viz. Saalmann et al. (2005), to which we will return below. Figure 1a is a reproduction of part of Greiner and neugebauer’s Fig. 9 (reconstruction before 175 Ma) with four geological provinces shown, as well as their postulated north American plate boundary coinciding with nares

The 2009 North Water anomaly

The North Water (NOW) polynya is an area of ocean between Greenland and Ellesmere Island that does not freeze completely during the winter months. The northern border of the polynya is typically demarked by an ice arch that forms across the narrow head of Smith Sound during winter. Once the ice arch consolidates, winds and current advect ice to the south, allowing the formation of new ice. The ice arch generally breaks down in late spring, at which point floes enter the region from the Arctic Ocean via Nares Strait. In 2009, the Smith Sound ice arch did not consolidate, but another ice arch formed 500 km to the north at the junction of Nares Strait and the Arctic Ocean. This northern ice arch prevented floes from reaching the NOW until 23 July and led to decadal low ice coverage for the region. In July, satellite-derived sea surface temperatures (SSTs) reached 8–10°C, which is approximately 5°C above typical seasonal values. With the introduction of floes into the NOW after 23 July, SSTs began to moderate.

The Canadian Arctic Archipelago throughflow in a multiresolution global model: Model assessment and the driving mechanism of interannual variability

The volume and freshwater transports through the Canadian Arctic Archipelago (CAA) are assessed using the unstructured‐mesh Finite Element Sea ice‐Ocean Model (FESOM) in a global setup with the CAA resolved at 5 km scale. The hindcast simulation realistically represents fluxes through the main gates of the Arctic Ocean and the Arctic sea ice conditions. During the period 1968–2007, the mean volume transports through Lancaster Sound and Nares Strait amount to 0.86 and 0.91 Sv, respectively. The monthly mean volume transport through western Lancaster Sound is highly correlated with the observational estimate (r = 0.81). The seasonal variability of the Lancaster Sound transport is well represented in the model. The simulated mean CAA freshwater export rate is 123 mSv, slightly higher than the observational estimate. The interannual variability of CAA volume transports is determined by sea surface height (SSH) gradients between the Arctic Ocean and northern Baffin Bay. The sea level upstream of Lancaster Sound is mainly determined by that along the Beaufort Sea coast, which can be explained by changes in the wind regimes (cyclonic versus anticyclonic) associated with release or accumulation of freshwater in the Beaufort Gyre. Sea level variations downstream of Lancaster Sound and Nares Strait are connected to SSH variations in the eastern Baffin Bay and in the Labrador Sea, which can be attributed to the variability of ocean‐atmosphere heat fluxes. Both processes upstream and downstream of the CAA are linked with the North Atlantic Oscillation type of atmospheric variability. The local mesh refinement of ∼5 km allows us to investigate the contribution of individual narrow straits to the Parry Channel volume transport. The volume transports through these straits show a very similar variability.

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

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 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 , approximately 13% of the total estimated FW increase in the Arctic in 2008.

Arctic‐scale assessment of satellite passive microwave‐derived snow depth on sea ice using Operation IceBridge airborne data

Snow depth on sea ice (SD) is a key geophysical variable, knowledge of which is critical for calculating the energy and mass balance budgets. Moreover, accurate knowledge of the SD distribution is important to retrieve sea‐ice thicknesses from altimetry data. So far, only space‐based microwave radiometers (e.g., Advanced Microwave Scanning Radiometer for Earth Observing System; AMSR‐E) provide operational SD on seasonal sea‐ice retrievals. A thorough assessment of these retrievals is needed on a large scale and on a variety of sea‐ice types. Our study presents such an assessment on Arctic sea ice using NASA's airborne Operation IceBridge (OIB) SDs, retrieved from radar measurements. Between 2009 and 2011, ∼610 12.5 km satellite grid cells were covered by seasonal sea ice where both satellite SD retrievals and OIB data were available. Using all the available data, the difference between the AMSR‐E product and the averaged OIB snow‐radar‐derived SD is 0.00±0.07 m. Satellite‐derived SD was accurate in the Beaufort Sea and the Canadian Archipelago but underestimated (∼0.07 m) in the Nares Strait. The RMSE between the two products ranges between 0.03 and 0.15 m. The RMSE is less than 0.06 m over a shallow snow cover (<0.20 m), in areas where satellite‐retrieved ice concentrations are higher than 90%, surface smooth, and ice thicker than ∼0.5 m. Locally the AMSR‐E algorithm can significantly underestimate SD. Several regions where the retrievals were less accurate (error >0.10 m) have been identified and related to the presence of either low ice concentration or significant fraction of multiyear ice within the grid cell that has not been flagged.

A new model for the Paleogene motion of Greenland relative to North America: Plate reconstructions of the Davis Strait and Nares Strait regions between Canada and Greenland

A simplified plate kinematic model for the Paleogene motion of Greenland relative to North America has been developed to provide a new framework for modeling the oceanic spreading system in Baffin Bay and the intraplate tectonic development of the Davis Strait and Nares Strait regions of the Arctic. A single Euler rotation pole was calculated for the C13N to C24N Eocene motion of the Greenland Plate relative to North America using spreading centers and fracture zones interpreted from satellite derived gravity data in Baffin Bay combined with fracture zones in Labrador Sea from published sources. A single stage pole is proposed for the C25N to C27N portion of the Paleocene and a short‐lived stage pole was found necessary to accommodate the C24N to C25N interval. This kinematic model has been used to reinterpret published shipborne magnetic profiles in central Baffin Bay to reveal a Paleocene spreading center and limits of both Eocene and Paleocene oceanic crust. Aeromagnetic data over northeastern Baffin Bay have been used to identify a new fracture zone in northern Baffin Bay. Plate reconstructions are presented incorporating constraints on plate boundaries from onshore and offshore geological and geophysical mapping. Within the Davis Strait, Paleocene oceanic crust was emplaced in an elongated rift that was subsequently inverted by approximately 300 km of Eocene transpression along the Ungava Fault Zone. In the Nares Strait Region, a “microplate” scenario is presented to explain the simultaneous formation of the Lancaster Sound Rift Basin and complex deformation within the Eurekan Orogenic Belt.

Geostrophic ocean currents and freshwater fluxes across the Canadian polar shelf via Nares Strait

Geostrophic ocean currents and freshwater fluxes across the Canadian polar shelf via Nares Strait

International Straits and Trans-Arctic Navigation

The Arctic Ocean is increasingly becoming accessible to international shipping as a result of the reduction in Arctic sea ice. Commercial shipping may seek to transit the Arctic Ocean from either the Pacific or Atlantic Ocean and, as a result, the legal regime of straits has significance for trans-Arctic navigation. In this article, current developments in Arctic shipping are assessed and consideration is given to certain Arctic straits that could prove to be pivotal in future Arctic navigation and shipping. These straits include the Bering Strait, Nares Strait, Davis Strait, Fram Strait, and Denmark Strait.