Beaufort-Chukchi Seas Research Articles

Arctic precipitation recycling and hydrologic budget changes in response to sea ice loss

With a declining sea ice cover, atmospheric moisture and precipitation in the Arctic increases because of the potential for increased evaporation, especially at the regional scale. We quantify the impact of sea ice decline on increasing atmospheric moisture availability from a locally-derived Arctic Ocean source. Between 1950 and 2019, Arctic precipitation recycling has increased from a predominant remote moisture source of 42% to a locally-driven cycle of more than 53% at a rate of 1.3% per decade. While there are almost no significant recycling trends in the summer months in any region, cold-season recycling increases are strongest in the Beaufort-Chukchi, Laptev, Kara, and East Siberian Seas, where sea ice area losses exhibit a strong negative relationship with regional recycling and local evaporation. Arctic-wide sea ice loss accounts for 32% of the increase in precipitation recycling, dominated by losses in the Beaufort-Chukchi Seas and the Central Arctic Basin. End-of-century model projections indicate further intensification of Arctic-wide recycling with rates of 60–64% by 2100, but are questionable at the regional scale due to a mismatch of evaporative and advected water vapor fluxes as compared to historical data. Models with realistic sea ice decline indicate that end-of-century net precipitation is higher than other previously reported estimates and will be between 2318 and 2734 km3 yr−1.

Modeled Stokes drift in the marginal ice zones of the Arctic Ocean

This study modeled Stokes drift in the marginal ice zone (MIZ) of the Arctic Ocean using WAVEWATCH III. Applying two viscoelastic and one empirical frequency-dependent wave–ice models, modeled wave parameters and spectra were compared with field observations from the Beaufort–Chukchi Sea. The three wave–ice parameterizations showed similar ability in reproducing the surface Stokes drift estimated using buoy measurements. Comparison with buoy drift showed the estimation of total surface drift was improved by considering Stokes drift during significant wave events. Based on 5-year (2015–2019) hindcasted directional spectra of the summer-autumn Arctic, we investigated monthly mean surface Stokes drift (1–10 cm/s), e-folding depth (1–14 m), and vertically integrated transport (< 0.23 m2/s) in the MIZ. The results showed that Stokes drift in the MIZ increased in strength from July to October. When bulk wave parameters were adopted to estimate Stokes drift fields, the surface Stokes drift was underestimated by about 34–50%, while the Stokes e-folding depth was overestimated by approximately 1.4–5.0 times, increasing from the interior to the edge of the ice cover. We compared the modeled surface Stokes drift with the Eulerian mean flow from reanalyzed data. It showed the mean surface Stokes drift is typically approximately 30% of the Eulerian current over large parts of the Arctic Ocean MIZ with mean ice concentration < 60%, and is the same order of magnitude as (or even larger than) some areas of the Chukchi, East Siberian, and Laptev Seas. It implies Stokes drift should be considered to improve modeling of the dynamic processes of sea ice, especially ice floe drift.

Arctic Intense Summer Storms and Their Impacts on Sea Ice—A Regional Climate Modeling Study

Various temporal and spatial changes have manifested in Arctic storm activities, including the occurrence of the anomalously intense storms in the summers of 2012 and 2016, along with the amplified warming and rapidly decreased sea ice. To detect the variability of and changes in storm activity and understand its role in sea ice changes, we examined summer storm count and intensity year-by-year from ensemble hindcast simulations with an Arctic regional coupled climate model for the period of 1948–2008. The results indicated that the model realistically simulated the climatological spatial structure of the storm activity, characterized by the storm count and intensity. The simulated storm count captures the variability derived from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP–NCAR) reanalysis, though the simulated one is higher than that in the reanalysis. This could be attributed to the higher resolution of the model that may better represent smaller and shallower cyclones. The composite analysis shows that intense storms tend to form a low-pressure pattern with centers over the Kara Sea and Chukchi Sea, respectively, generating cyclonic circulation over the North Atlantic and North Pacific Arctic Ocean. The former drives intensification of the transpolar drift and Fram Strait sea ice export, and the latter suppresses thick ice transport from the Canada Basin to the Beaufort–Chukchi Seas, in spite of an increase in sea ice transport to the East Siberian Sea. Associated with these changes in sea ice transport, sea ice concentration and thickness show large decreases in the Barents–Kara Seas and the Chukchi–East-Siberian Seas, respectively. Energy budgets analysis suggests that more numerous intense storms substantially decrease the downward net sea ice heat fluxes, including net radiative fluxes, turbulent fluxes, and oceanic heat fluxes, compared with that when a lower number of intense storms occur. The decrease in the heat fluxes could be attributable to an increased cloudiness and the resultant reduction of downward shortwave radiation, as well as a destabilized boundary layer induced increase in upward turbulent fluxes.

Arctic underwater noise transients from sea ice deformation: Characteristics, annual time series, and forcing in Beaufort Sea.

A 13-month time series of Arctic Ocean noise from the marginal ice zone of the Eastern Beaufort Sea is analyzed to detect under-ice acoustic transients isolated from ambient noise with a dedicated algorithm. Noise transients due to ice cracking, fracturing, shearing, and ridging are sorted out into three categories: broadband impulses, frequency modulated (FM) tones, and high-frequency broadband noise. Their temporal and acoustic characteristics over the 8-month ice covered period, from November 2005 to mid-June 2006, are presented and their generation mechanisms are discussed. Correlations analyses showed that the occurrence of these ice transients responded to large-scale ice motion and deformation rates forced by meteorological events, often leading to opening of large-scale leads at main discontinuities in the ice cover. Such a sequence, resulting in the opening of a large lead, hundreds by tens of kilometers in size, along the margin of landfast ice and multiyear ice plume in the Beaufort-Chukchi seas is detailed. These ice transients largely contribute to the soundscape properties of the Arctic Ocean, for both its ambient and total noise components. Some FM tonal transients can be confounded with marine mammal songs, especially when they are repeated, with periods similar to wind generated waves.

Relationship between Arctic sea ice thickness distribution and climate of China

Based on the simulated ice thickness data from 1949 to 1999, monthly mean temperature data from 160 stations, and monthly mean 1°×1° precipitation data reconstructed from 749 stations in China from 1951 to 2000, the relationship between the Arctic sea ice thickness distribution and the climate of China is analyzed by using the singular value decomposition method. Climate patterns of temperature and precipitation are obtained through the rotated empirical orthogonal function analysis. The results are as follows. (1) Sea ice in Arctic Ocean has a decreasing trend as a whole, and varies with two major periods of 12–14 and 16–20 yr, respectively. (2) When sea ice is thicker in central Arctic Ocean and Beaufort-Chukchi Seas, thinner in Barents-Kara Seas and Baffin Bay-Labrador Sea, precipitation is less in southern China, Tibetan Plateau, and the north part of northeastern China than normal, and vice versa. (3) When sea ice is thinner in the whole Arctic seas, precipitation is less over the middle and lower reaches of Yellow River and north part of northeastern China, more in Tibetan Plateau and south part of northeastern China than normal, and the reverse is also true. (4) When sea ice is thinner in central Arctic Ocean, East Siberian Sea, Beaufort-Chukchi Seas, and Greenland Sea; and thicker in Baffin Bay-Labrador Sea, air temperature is higher in northeastern China, southern Tibetan Plateau, and Hainan Island than normal. (5) When sea ice is thicker in East Siberian Sea 5 months earlier, thinner in Baffin Bay-Labrador Sea 7–15 months earlier, air temperature is lower over the north of Tibetan Plateau and higher in the north part of northwestern China than normal, and a reverse correlation also exists.

Lactational transfer of mercury and polychlorinated biphenyls in polar bears

We examined concentrations of total mercury (tHg, inorganic and methylated forms) and polychlorinated biphenyls (PCBs) in blood and milk from free-ranging Southern Beaufort–Chukchi Sea polar bears (Ursus maritimus) to assess maternal transfer of contaminants during lactation and the potential health risk to nursing young. Concentrations of contaminants in the blood of dependent and juvenile animals (ages 1–5years) ranged from 35.9 to 52.2μgkg−1ww for tHg and 13.9 to 52.2μgkg−1ww (3255.81–11067.79μgkg−1lw) for ΣPCB7s, similar to those of adult females, but greater than adult males. Contaminant concentrations in milk ranged from 5.7 to 71.8μg tHg kg−1ww and 160 to 690μg ΣPCB11s kg−1ww (547–5190μgkg−1lw). The daily intake levels for tHg by milk consumption estimated for dependent young were below the tolerable daily intake level (TDIL) of tHg established for adult humans. Although the daily intake levels of PCBs through milk consumption for cubs of the year exceeded the TDIL thresholds, calculated dioxin equivalents for PCBs in milk were below adverse physiological thresholds for aquatic mammals. Relatively high concentrations of non-dioxin like PCBs in polar bear milk and blood could impact endocrine function of Southern Beaufort–Chukchi Sea polar bears, but this is uncertain. Transfer of contaminants during mid to late lactation likely limits bioaccumulation of dietary contaminants in female polar bears during spring. As polar bears respond to changes in their arctic sea ice habitat, the adverse health impacts associated with nutritional stress may be exacerbated by tHg and PCBs exposure, especially in ecologically and toxicologically sensitive polar bear cohorts such as reproductive females and young.

Long-Range Statistical Forecasting of Ice Severity in the Beaufort–Chukchi Sea

Abstract Interannual variations in Beaufort Sea summer ice conditions influence a wide range of socioeconomic activities, including merchant shipping in the Beaufort Sea and subsistence lifestyles on the Alaskan North Slope. Each year, the National Ice Center quantifies Beaufort Sea summer ice conditions based on the Barnett severity index (BSI), which is based on distances from Point Barrow, Alaska, to the sea ice edge, as well as characteristics of the shipping season from Prudhoe Bay to the Bering Sea. Long-range forecasts (monthly to seasonal) of the BSI would be valuable for the above-mentioned users, provided that the forecasts are communicated effectively and used properly. Utilizing mean monthly sea ice and atmospheric data from 1979 through 2000, multiple linear regression models are developed here to forecast the BSI at monthly intervals from October of the previous year through to July of the prediction year. The final models retain between three and five variables, with decreased multiyear sea...

Enantiomer-specific biomagnification of alpha-hexachlorocyclohexane and selected chiral chlordane-related compounds within an Arctic marine food web.

Concentrations of achiral and chiral organochlorine contaminants (OCs), including hexachlorocyclohexane isomers (HCH), chlordane congeners (cis- and trans-chlordane, cis- and trans-nonachlor, MC5, MC7, and U82), and related metabolites (oxychlordane [OXY] and heptachlor exo-epoxide [HEPX]), were quantified in seawater (100 L; n = 6) and biota from the coastal Beaufort-Chukchi Seas food web near Barrow (AK, USA). The biota included zooplankton (Calanus spp.; n = 5), fish species such as arctic cod (Boreogadus saida; n = 10), arctic char (Salvelinus alpinus; n = 3), and marine mammals including bowhead whales (Balaena mysticetus; liver: n = 23; blubber: n = 40), beluga whales (Delphinapterus leucas; blubber: n = 20), ringed seals (Phoca hispida; blubber: n = 20), and bearded seals (Erignathus barbatus; blubber: n = 7). The food web magnification factors (FWMFs) for HCHs and chlordane compounds ranged from 0.5 (gamma-HCH) to 6.5 (HEPX) and were expected based on known recalcitrance and biotransformation of OCs. The enantiomer fractions (EFs) of all chiral OCs were near racemic (EF = 0.50) in the seawater, zooplankton, and all fish analyzed. In contrast, the EFs for most OCs analyzed were nonracemic (EF # 0.50) in the marine mammals blubber (range: 0.09-0.79) because of enantiomer-specific biotransformation and (or) accumulation. However, EF values were not significantly correlated with isotopically determined trophic level. The EFs for all chiral OCs (except alpha-HCH) in bowhead whale liver closely approximated the values in zooplankton, suggesting that the accumulation of chiral OCs from prey into this cetacean is not enantiomer specific. However, the modification of EFs from bowhead liver to blubber suggests that this species has the ability to enantioselectively biotransform and accumulate several chiral OC compounds.

Trophic transfer of persistent organochlorine contaminants (OCs) within an Arctic marine food web from the southern Beaufort–Chukchi Seas

Stable isotope values (δ 13C, δ 15N) and concentrations of persistent organochlorine contaminants (OCs) were determined to evaluate the near-shore marine trophic status of biota and biomagnification of OCs from the southern Beaufort–Chukchi Seas (1999–2000) near Barrow, AK. The biota examined included zooplankton ( Calanus spp.), fish species such as arctic cod ( Boreogadus saida), arctic char ( Salvelinus alpinus), pink salmon ( Oncorhynchus gorbuscha), and fourhorn sculpin ( Myoxocephalus quadricornis), along with marine mammals, including bowhead whales ( Balaena mysticetus), beluga whales ( Delphinapterus leucas), ringed seals ( Phoca hispida) and bearded seals ( Erignathus barbatus). The isotopically derived trophic position of biota from the Beaufort–Chukchi Seas marine food web, avian fauna excluded, is similar to other coastal food webs in the Arctic. Concentrations of OCs in marine mammals were significantly greater than in fish and corresponded with determined trophic level. In general, OCs with the greatest food web magnification factors (FWMFs) were those either formed due to biotransformation (e.g. p,p′-DDE, oxychlordane) or considered recalcitrant (e.g. β-HCH, 2,4,5-Cl substituted PCBs) in most biota, whereas concentrations of OCs that are considered to be readily eliminated (e.g. γ-HCH) did not correlate with trophic level. Differences in physical–chemical properties of OCs, feeding strategy and possible biotransformation were reflected in the variable biomagnification between fish and marine mammals. The FWMFs in the Beaufort–Chukchi Seas region were consistent with reported values in the Canadian Arctic and temperate food webs, but were statistically different than FWMFs from the Barents and White Seas, indicating that the spatial variability of OC contamination in top-level marine Arctic predators is attributed to differences in regional sources of contamination rather than trophic position.

On the origin and evolution of sea-ice anomalies in the Beaufort-Chukchi Sea

The origin and space-time evolution of Beaufort-Chukchi Sea ice anomalies are studied using data and a recently developed dynamic-thermodynamic sea-ice model. First, the relative importance of anomalies of river runoff, atmospheric temperature and wind in creating anomalous sea-ice conditions in the Beaufort-Chukchi Sea is investigated. The results indicate that wind anomalies are the dominant factor responsible for creating interannual variability in the Beaufort-Chukchi Sea ice cover. Temperature anomalies appear to play a major role for longer time scale fluctuations, whereas the effects of runoff anomalies are small. The sea-ice model is then used to track the position of a positive sea-ice anomaly as it is transported by the Beaufort Gyre toward the Transpolar Drift Stream and then exported out of the Arctic Basin into the Greenland Sea via Fram Strait. The model integration shows that sea-ice anomalies originating in the western Beaufort Sea can survive a few seasonal cycles as they propogate through the Arctic Basin and can account for a notable amount of anomalous ice export into the Greenland Sea. These anomalies, however, represent a small contribution to the fresh water budget in this area when compared with sea-ice fluctuations generated by interannually varying local winds.

The fast ice regimes of the Beaufort and Chukchi Sea coasts, Alaska

The annual fast ice regimes of the Beaufort-Chukchi Sea coasts are characterized from an analysis of LANDSAT imagery for 1973–76. Maps of the fast ice margin are presented and factors determining its spatial and temporal variability are discussed. The summer decay pattern is influenced by the previous winter's grounded ridges, the distribution of river flooding and local polynyi, and by the climatic regime. Thawing degree days are a useful index of ice decay, although temperature conditions themselves are strongly determined by wind directions on both coasts. Potential ice hazards of the nearshore zone in the Beaufort Sea for offshore developments are discussed.