Where Ice Meets the Ocean: Outer Coast Field Update for 2022

NPS/Jamie Womble

The Southeast Alaska Network and the University of Alaska College of Fisheries and Ocean Sciences completed the inaugural oceanographic and seabird and marine mammal monitoring mission along the outer coasts of Wrangell-St. Elias and Glacier Bay national parks and preserves from the R/V Wolstad, 2-9 June 2022. The primary objective was to characterize fjord and nearshore marine conditions along the outer coast in Disenchantment Bay, Yakutat Bay, Icy Bay, and Lituya Bay. This effort represents the first synoptic physical and biological oceanographic surveys in tidewater glacier fjords in this remote region of the eastern Gulf of Alaska. The mission included physical, chemical, and biological oceanographic sampling at about 70 stations and concurrent marine bird and mammal surveys in tidewater glacier fjords and nearshore regions along the outer coast (Figure 1).

Figure 1. A map of the sampling area describing what kind of data were collected and where.

Summary of Preliminary Results

• Ocean Temperature. Observed water column temperatures varied from below 4 °C (in Icy Bay near melting ice) to above 11 °C (outside of fjords on the shelf, near-surface; Figure 2). Salinity ranged from close to 32 (near-bottom, offshore) to 31-31.5 (subsurface within fjords) to 25-30.5 (surface). Near-surface stratification generally confined the mixed layer depth to the upper 33 feet (10 m) of the water column.

Figure 2. Temperature (°C) and salinity profiles for Icy Bay, Yakutat and Disenchantment Bays, and Lituya Bay observed during the 2022 Outer Coast mission.

Deployment of a CTD (conductivity, temperature, and depth) rosette equipped with Niskin water sampling bottles near Lituya Bay.

NPS/Jamie Womble

• Freshwater Plumes, Density Fronts, and Turbidity. We observed a series of density fronts that were often associated with bathymetric features (e.g., sills) and freshwater plumes that resulted from melting tidewater glaciers and icebergs. Turbidity levels increased in association with melting ice (close to glaciers, even throughout the water column in northern Disenchantment Bay), chlorophyll blooms (near-surface), and in other waters that had coloration indicating the presence of glacial till.
• Nutrients. Concentrations of the macronutrients nitrate, phosphate, and silicic acid that are necessary for photosynthesis and phytoplankton growth were low in all four fjords. Nutrient concentrations were generally higher on the shelf side of the transects compared to the head of the bays near glaciers and sources of freshwater inputs. Low nutrient concentrations resulted in low concentrations of chlorophyll-a—a pigment used to estimate phytoplankton biomass—over the entire study region with phytoplankton detected in the upper 65 feet (20 m) of the water column.
• Phytoplankton. The phytoplankton communities in each bay were composed of small-sized phytoplankton in the nano- and picoplankton size categories (0.7-20 µm) with little contribution from the larger diatom phytoplankton species (>20 µm). A peak in diatoms at the head of Icy Bay was associated with the freshwater lens formed from ice melt.

• Zooplankton. Zooplankton community composition within the fjords were primarily composed of small- to medium-sized copepods, such as the cyclopoid copepod Oithona similis and calanoid copepods Calanus marshallae, Acartia longiremis, and the Pseudocalanus species complex consisting of P. newmani, P. mimus, and P. minutus. Other notable members of the zooplankton community included juvenile euphausiids (krill) and the pteropod (pelagic snail) Limacina helicina.
• Ocean Acidification. Ocean acidification conditions were evaluated for each fjord by determining the saturation states of the calcium carbonate minerals calcite (Ω_Ca) and aragonite (Ω_Ar; Figure 3); calcite and aragonite are essential minerals for calcifying marine organisms such as pteropods, crustaceans, and echinoderms. All four bays exhibited an oversaturation (Ω >1) with respects to calcite, indicating favorable conditions for calcifying marine organisms. Pockets of water nearing undersaturation (Ω <1) were observed in Yakutat Bay and in shelf waters off and within Lituya Bay. In all four bays, Ω_Ar was low with undersaturated waters congruent with low Ω_Ca conditions.

Figure 3. Ocean acidification parameters of calcite (Ca; top graphs) and aragonite (Ar; bottom graphs) saturation states for Icy Bay, Yakutat and Disenchantment Bays, and Lituya Bay observed during the 2022 Outer Coast mission.

Oceanographic mooring being deployed in Disenchantment Bay.

NPS/Jamie Womble

• Jellyfish Bloom in Lituya Bay. A large bloom of the jellyfish Aequoria victoria (Cnidaria) was observed in Lituya Bay. The high densities are likely a result of the warm sea surface temperatures and entrapment in the bay due to the narrow entrance and tidal cycles.

• Oceanographic Mooring for Monitoring High-Resolution Physical and Chemical Parameters in Disenchantment Bay. An over-wintering oceanographic biophysical mooring was deployed in Disenchantment Bay. The mooring was set up to collect high-resolution physical, bio-optical data and underwater sound recordings. The mooring was designed to be recovered and re-deployed annually.

• Seabirds and Marine Mammals
  • Seabird species observed along transects included marbled murrelets, Kittlitz’s murrelets, glaucous-winged gulls, black-legged kittiwakes, common murres, pelagic cormorants, and Arctic terns
  • Cenotaph Island in Lituya Bay is home to a large black-legged kittiwake colony along with several pelagic cormorants.
  • Harbor porpoise were observed in Lituya Bay and Disenchantment Bay.
  • Large aggregations of harbor seals (including pups) were observed resting on icebergs in Disenchantment Bay and Icy Bay in coastal Wrangell-St. Elias National Park and Preserve. Currently, Icy Bay hosts the largest seasonal aggregations of harbor seals in Alaska and the world. In the mid-1990s, tidewater glaciers in Lituya Bay provided iceberg habitat for seals; however, since those glaciers have grounded, seals no longer use ice habitat in the bay.
  • Sea otters were observed in all fjords and generally associated with nearshore areas and foraging over and near glacial sills.
  • Approximately 270 Steller sea lions were primarily observed hauled out along a series of nearshore rocks near the entrance of and south of Lituya Bay.

A colony of black-legged kittiwakes on Cenotaph Island (above, left), a harbor seal and her pup (above, middle), and Steller sea lions hauled out in Lituya Bay (above, right).

NPS/Jamie Womble