A model-based examination of multivariate physical modes in the Gulf of Alaska

Hermann, Albert J.; Ladd, Carol; Cheng, Wei; Curchitser, Enrique N.; Hedstrom, Kate

doi:10.1016/j.dsr2.2016.04.005

Cited by 19 publications

(8 citation statements)

References 32 publications

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“…These are, however, volume averages for the top 300 m and over a large spatial region; locally and near the surface changes in T and S are more substantial. The warmer and fresher T GOA and S GOA during a positive PDO phase are consistent with the expected water properties variations for the GOA associated with the PDO (Hermann et al, 2016;Cummins & Masson, 2018).…”

Section: Geostrophic Contribution To Temperature and Salinity Variabisupporting

confidence: 84%

“…These near‐shelf values for the meridional transport should, however, be considered with caution since they are sensitive to the limited near‐costal spatial coverage of the data sets used here. Nevertheless, the overall implications of a stronger Alaska Gyre and weak modal amplitude in the eastern GOA (as compared to the western GOA) during a positive phase of the PDO are consistent with model‐based multivariate analysis (Hermann et al, ).…”

Section: Comparison Of Steric Height and Ssh For The Northeast Pacificsupporting

confidence: 74%

“…Temperature and salinity, volume‐averaged for the GOA and the top 300 m, are also strongly affected by the PDO, with warmer and fresher waters during a positive phase (Cummins & Masson, ; Hermann et al, ). The covariability between northward geostrophic transport anomalies and water property variability in the GOA suggest a possible advective contribution from the south (Figure ).…”

Section: Discussionmentioning

confidence: 99%

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Variability and Trends of the Alaska Gyre From Argo and Satellite Altimetry

2019

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The interannual variability and trends of the Alaska Gyre and Gulf of Alaska (GOA) circulation are examined using meridional geostrophic transport from Argo temperature and salinity (2004–2017) and altimetric sea surface height (1993–2017). More than half of the top 1,500 m meridional transport variability in the Alaska Gyre is accounted for by a statistical mode strongly correlated with the Pacific Decadal Oscillation (PDO) index, consistent with the PDO exerting a major influence on North Pacific sea surface temperature variability. During a positive phase of the PDO, the zero‐transport streamline separating the subtropical from the Alaska Gyre is shifted to the south from its mean position, while more transport is diverted northward, associated with a stronger and larger Alaska Gyre. Additionally, over the 25‐year altimetric record there is a linear, increasing trend in strength of the Alaska Gyre (but not in areal extent), accompanied by an increasing trend for the incoming North Pacific Current. The effect of the PDO transport mode on GOA circulation is weak. Temperature and salinity volume averaged for the GOA covary with the PDO index, with warmer and fresher waters during a positive phase. Despite correlated anomalies for temperature, salinity, and northward transport into the GOA, however, geostrophic advection from the south contributes only minimally to the interannual variations of water properties in the GOA. An exception was the marine heat wave of 2013/2014 and its aftermath when temperature advection from the south played a more appreciable role for warming and subsequent cooling of the GOA.

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Section: Geostrophic Contribution To Temperature and Salinity Variabisupporting

confidence: 84%

Section: Comparison Of Steric Height and Ssh For The Northeast Pacificsupporting

confidence: 74%

Section: Discussionmentioning

confidence: 99%

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Variability and Trends of the Alaska Gyre From Argo and Satellite Altimetry

2019

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“…A definitive spring bloom occurs between March‐May, with lower but sustained productivity throughout summer when downwelling conditions are relaxed and peak glacial discharge occurs (Coyle et al, ). On interannual timescales, both atmospheric and hydrographic features of the GOA are significantly modulated by global patterns such as the El Niño–Southern Oscillation (Hermann et al, , ).…”

Section: Introductionmentioning

confidence: 99%

Simulated Impact of Glacial Runoff on CO₂ Uptake in the Gulf of Alaska

Pilcher

Siedlecki

Hermann

et al. 2018

Geophysical Research Letters

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The Gulf of Alaska (GOA) receives substantial summer freshwater runoff from glacial meltwater. The alkalinity of this runoff is highly dependent on the glacial source and can modify the coastal carbon cycle. We use a regional ocean biogeochemical model to simulate CO2 uptake in the GOA under different alkalinity‐loading scenarios. The GOA is identified as a current net sink of carbon, though low‐alkalinity tidewater glacial runoff suppresses summer coastal carbon uptake. Our model shows that increasing the alkalinity generates an increase in annual CO2 uptake of 1.9–2.7 TgC/yr. This transition is comparable to a projected change in glacial runoff composition (i.e., from tidewater to land‐terminating) due to continued climate warming. Our results demonstrate an important local carbon‐climate feedback that can significantly increase coastal carbon uptake via enhanced air‐sea exchange, with potential implications to the coastal ecosystems in glaciated areas around the world.

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“…The winds in the winter mix the shelf down to 100–200 m. The runoff contribution to the shelf is massive (∼24,000 m 3 s −1 ; or 20% greater than the Mississippi River discharge) and in combination with wind forcing affects shelf dynamics, stratification, nutrient loads, and carbon biogeochemistry. The principal drivers of this shelf ecosystem also vary substantially at interannual and longer time scales (Hermann et al, ; Royer, ; Stabeno et al, ; Weingartner et al, ), although the variability is poorly understood.…”

Section: Introductionmentioning

confidence: 99%

The Importance of Freshwater to Spatial Variability of Aragonite Saturation State in the Gulf of Alaska

et al. 2017

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High‐latitude and subpolar regions like the Gulf of Alaska (GOA) are more vulnerable than equatorial regions to rising carbon dioxide (CO2) levels, in part due to local processes that amplify the global signal. Recent field observations have shown that the shelf of the GOA is currently experiencing seasonal corrosive events (carbonate mineral saturation states Ω, Ω < 1), including suppressed Ω in response to ocean acidification as well as local processes like increased low‐alkalinity glacial meltwater discharge. While the glacial discharge mainly influences the inner shelf, on the outer shelf, upwelling brings corrosive waters from the deep GOA. In this work, we develop a high‐resolution model for carbon dynamics in the GOA, identify regions of high variability of Ω, and test the sensitivity of those regions to changes in the chemistry of glacial meltwater discharge. Results indicate the importance of this climatically sensitive and relatively unconstrained regional freshwater forcing for Ω variability in the nearshore. The increase was nearly linear at 0.002 Ω per 100 µmol/kg increase in alkalinity in the freshwater runoff. We find that the local winds, biological processes, and freshwater forcing all contribute to the spatial distribution of Ω and identify which of these three is highly correlated to the variability in Ω. Given that the timing and magnitude of these processes will likely change during the next few decades, it is critical to elucidate the effect of local processes on the background ocean acidification signal using robust models, such as the one described here.

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A model-based examination of multivariate physical modes in the Gulf of Alaska

Cited by 19 publications

References 32 publications

Variability and Trends of the Alaska Gyre From Argo and Satellite Altimetry

Variability and Trends of the Alaska Gyre From Argo and Satellite Altimetry

Simulated Impact of Glacial Runoff on CO₂ Uptake in the Gulf of Alaska

The Importance of Freshwater to Spatial Variability of Aragonite Saturation State in the Gulf of Alaska

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A model-based examination of multivariate physical modes in the Gulf of Alaska

Cited by 19 publications

References 32 publications

Variability and Trends of the Alaska Gyre From Argo and Satellite Altimetry

Variability and Trends of the Alaska Gyre From Argo and Satellite Altimetry

Simulated Impact of Glacial Runoff on CO2 Uptake in the Gulf of Alaska

The Importance of Freshwater to Spatial Variability of Aragonite Saturation State in the Gulf of Alaska

Contact Info

Product

Resources

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Simulated Impact of Glacial Runoff on CO₂ Uptake in the Gulf of Alaska