Pearson cross-correlations with total exploitable biomass (tonnes) versus sea ice and climate system indices (North Atlantic Oscillation, NAO; Southern Oscillation, SO; Pacific Decadal Oscillaion, PDO) as well as cod biomass indices (tonnes) by Stock Region (Alaska, AK; Newfoundland and Labrador, NL; southern Gulf of St. Lawrence, sGSL).

Pearson cross-correlations with total exploitable biomass (tonnes) versus sea ice and climate system indices (North Atlantic Oscillation, NAO; Southern Oscillation, SO; Pacific Decadal Oscillaion, PDO) as well as cod biomass indices (tonnes) by Stock Region (Alaska, AK; Newfoundland and Labrador, NL; southern Gulf of St. Lawrence, sGSL).</p

Fig 1 -

Left. Artic Circle view of the northern hemisphere showing the nine sea Ice Regions considered in analysis. Dashed circle shows Arctic Circle delineation. Right. Top Row: Snow crab total exploitable biomass index by Stock Region (AK = Alaska, NL = Newfoundland & Labrador, sGSL = Southern Gulf of St. Lawrence). Second Row: Maximum sea ice extent index by snow crab Stock Region. Third Row: Cod biomass index by snow crab Stock Region. Fourth Row: Annual Arctic Oscillation and North Atlantic Oscillation Indices. Bottom Row: Annual Pacific Decadal and Southern Oscillation Indices. Map source file “The Blue Marble” modified from and credited to NASA Earth Observations (https://neo.gsfc.nasa.gov/view.php?datasetId=BlueMarbleNG-TB). Snow crab distribution is related to seasonal ice cover. Globally, areas either perpetually or ephemerally covered in sea ice do not support large stock biomasses. In cases where exceptions occur, such as in the southernmost (ice-free) extent of the Atlantic Canadian stock range (Nova Scotia), direct cold water inputs from adjacent ice-covered ecosystems occur (Petrie and Drinkwater, 1993). In recent decades, increased ice free periods in Arctic Regions have enabled habitat shifts for snow crab. Numerous recent observations of increasing abundances or first occurrences in Arctic waters (i.e. north of 66.56°N) such as the Chukchi [2], Beaufort [3], Barents [4]), Kara [5], and East Siberian and Laptev Seas [6] collectively confirm that the distribution of snow crab is now near-circumpolar and that the species should no longer be characterized as sub-Arctic.</p

Future Habitat Model (FHM) outputs by Ice Region (Total Arctic [TotArc], Arctic Ocean [ArcOcn], Canadian Archipelago [CanArch], Huddon Bay [Hudson], East Greenland [EGreen], Barents and Kara Seas [BarKara], Baffin Bay and Newfoundland & Labrador [BaffNL], Southern Gulf of St. Lawrence [sGSL], Bering Sea [Bering], and Seas of Okhotsk and Japan [OkhJpn]).

Predictor terms are calendar month, Arctic Oscillation (AO) and carbon dioxide (CO2). edf refers to effective degrees of freedom, Ref.df refers to reference degrees of freedom, and dev.expl. refers to deviance explained.</p

Future habitat model (FHM) of predicted versus observed values of ice extent by Ice Region and year.

Future habitat model (FHM) of predicted versus observed values of ice extent by Ice Region and year.</p

Short-term prediction model of biomasses for Alaska (AK), Newfoundland & Labrador (NL), and southern Gulf of St. Lawrence (sGSL) stock units.

Black squares are survey indices (2020 in Alaska is model estimate). Black lines and dots and associated error bars are full model fits (short-, mid-, long-term effects) and red lines and dots and error bars are model run with no short-term effects. Shaded areas are 95% confidene intervals of model fits.</p

Fig 8 -

Left. Marginal effect smooths of monthly ice extent patterns by Ice Region. Right. Contour plots of smoothed interaction effects of atmospheric CO2 concentration and the Arctic Oscillation on ice extent in the Future Habitat Model (FHM).</p

Snow crab potential habitat index by Ice Region.

Black points show ice extent areas based on historic NOAA satellite observations of maximum minus minimum ice extent in a calendar year. Black lines are loess regression curves. Blue and red solid lines are best- and worst-case CO2 emission scenarios projections, with the index calculated from model point estimates of maximum and minimum monthly ice extent values. Thin-dashed black lines show upper and lower 95% confidence interval bounds for model fits. Corresponding thin-dashed blue and red lines show upper (95th percentile) and lower (5th percentile) levels of predicted ice extent for a given calendar year. Lowest levels of ice predictions equal to zero in the worst-case scenario model run are plotted below zero for presentation.</p

Ice extent indices by Ice Region grouped as new frontiers, historic ranges, and overall area.

Maximum and minimum based on annual observations and Habitat Potential based on difference of maximum-minimum values. Data from NOAA satellite observations.</p

Historic data on monthly ice extent values from NOAA satellite observations by Ice Region (black dots) with Future Habitat Model fits (black lines) and 95% confidence intervals (gray shades).

Blue and red lines show projections under best and worst case CO2 emissions scenarios respectively. Red and blue shaded areas represent bootstrapped 95% prediction intervals. Data are fit by month with calendar years restricted to those indicated on the x-axis. Vertical solid black lines show January and vertial dashed black lines show December. Horizontal green line on Total Arctic panel (top panel) shows 1 million square kilometres ice coverage level.</p

Observed (black) versus predicted (red) ice extent (million km²) by month from 1980 to 2020 by Ice Region.

Observed data are from NOAA satellite observations and predicted ata are from the Future Habitat Model. Horizontal lines and associated 95% confidence intervals are loess regression curves fit to the data for visual assessment of mean trends. Maximum Ice Regions refer to those consistently full of ice during the calendar year, Minimum Ice Regions refer to those consistently fully deplete of ice during the calendar year, and Variable Ice Regions refer to those neither consistently full nor deplete of ice during the calendar year.</p