ABSTRACT:

This study examines the impact of climate variability on glaciers in the Olympic Mountains, Washington State, USA. The area is known for a significant precipitation gradient, with annual rainfall varying from 6.5 meters on the west-facing slopes to 0.5 meters in the northeast lowlands. We are investigating the hypothesis that past variations in glacier extent were influenced by this spatial variability in precipitation.

Our analysis relies on data from the Weather Research and Forecasting (WRF) model, captured during the Olympic Mountain Experiment (OLYMPEX) campaign of 2015-2016. This data offers a valuable source of detailed information about the region's climate dynamics.

The first dataset, "OLYMPICS_ELWHA_QUINAULT_6-HOUR_MEANS.csv," contains average precipitation data within the Elwha and Quinault basins for each 6-hour model run. This information helps to show how precipitation patterns vary within these basins over time.

The second dataset, "OLYMPEX_RAINNC_TOTAL.tif," includes the total sum of the RAINNC variable, which represents total precipitation, for the entirety of the OLYMPEX campaign. This comprehensive data provides a clear picture of overall precipitation levels during the study period.

By using these datasets, we aim to gain a better understanding of the relationship between precipitation and glacier extent in the Olympic Mountains. This knowledge is crucial for assessing the effects of climate change in this region and others with similar climate patterns.

ABSTRACT:

This MATLAB program is designed to simulate the flow dynamics of glaciers within the Elwha and Quinault basins, situated in the Olympic mountains. Using parameters that affect glacial flow, such as the density of ice, the gravitational pull, and the coefficients for deformation and sliding of the glacier, this model provides an insight into the process of glacial evolution.

The model initializes by importing the desired glacier profile from two available .mat files, "Elwha_Basin_Input.mat" or "Quinault_Basin_Input.mat," which provide comprehensive data about the unique conditions of the Elwha and Quinault basins, respectively. The geometric attributes of the glacier, including its bed elevation and width, are then meticulously defined and interpolated onto a calculated grid for accurate modelling.

Climate parameters integral to the functioning of glaciers are also incorporated into this model, encompassing annual precipitation rates, sea-level temperature, and the melt factor. These values, along with other parameters, feed into the critical computation of the mass balance of the glacier, which balances the accumulation against the melting of the glacier ice.

At the heart of the simulation is a time-stepping loop that updates and records the glacier's height, thickness, and the rate of change of thickness over the defined period. This iterative approach provides dynamic results that demonstrate the evolution of the glacier over time, providing outputs of both glacier height and thickness at each time step.

The generated outputs from this model provide an invaluable resource for understanding glacial behavior and the effects of varying climatic conditions on glaciers. This can be of great use in broader studies of climate change and its impact on glacial ecosystems, providing a data-driven foundation for further research and policy making.

ABSTRACT:

Glaciers are sensitive to temporal climate variability. Glacier sensitivity to spatial variability in climate has been much less studied. The Olympic Mountains of Washington State, USA, experience a pronounced orographic precipitation gradient with modern annual precipitation ranging between ~6500 and ~500 mm water equivalent. In the Quinault Valley, on the wet side of the range, a glacier extended onto the coastal plain reaching a maximum position during the early Wisconsin. On the dry side of the range, in the Elwha Valley, there is no evidence of a large paleoglacier during the Wisconsin. We hypothesize that asymmetry in past glacier extent was driven by spatial variability in precipitation. To evaluate this hypothesis, we constrain the past precipitation gradient, and model glacier extent. We explore variability in observed and modelled precipitation gradients over timescales from 6 hours to ~100 years. Across three data sets, basin-averaged precipitation in the Elwha is 54% of that in the Quinault. Our analysis overwhelmingly indicates spatially coherent variability in precipitation across the peninsula. We conclude that the past precipitation gradient was likely similar to the modern gradient. We use a one-dimensional glacier flowline model, driven by sea-level summer temperature and annual precipitation to approximate glacier extent in the Quinault and Elwha Valleys. We find several equilibrium states for the Quinault Glacier at the mapped maximum position within paleoclimate constraints for cooling and drying, relative to present-day conditions. Assuming stable precipitation gradients, we model Elwha glacier extent for the climates of these equilibria. At the warm end of the paleoclimate constraint (July average sea-level temperature of 10.5 ˚C), a small valley glacier occurs in the high headwaters of the Elwha Valley. Yet, for the cooler end of the allowable paleoclimate (July average sea-level temperature of 7 ˚C), the Elwha Glacier advances to a narrow notch in the valley, thickens, and rapidly extends far beyond the likely true maximum extent. Therefore, we suggest that the last glacial maximum climate was more likely to have been relatively warm because our models of glacial extent are consistent with the past record of glaciation in both the Quinault Valley and Elwha Valley for warm conditions, but inconsistent for cooler conditions. Alternatively, spatially variable drivers of ablation including differences in cloudiness could have contributed to past asymmetry in glacier extent. Future research to constrain past precipitation gradients and evaluate their impact on glacier dynamics is needed to better interpret the climatic significance of past glaciation and to predict future response of glaciers to climate change.